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INTERNATIONAL SYMPOSIUM ON MUSICAL ACOUSTICS

19-22 August 1997

Abstracts of Papers

With page numbers in the Proceedings

Web URL:- http://www.music.ed.ac.uk/euchmi/isma/mta.html

ISMA '97 Organising Committee

D. Murray Campbell (University of Edinburgh); Peter Dobbins (BAeSEMA); Clive Greated (University of Edinburgh); Catherine Mackenzie (Institute of Acoustics); Arnold Myers (University of Edinburgh); Peter Nelson (University of Edinburgh); Bernard E. Richardson (University of Cardiff); James Woodhouse (University of Cambridge)

ISMA '97 Scientific Committee

Xavier Boutillon (France); Neville Fletcher (Australia); Avraham Hirschberg (Netherlands); Carleen Hutchins (U.S.A.); Jürgen Meyer (Germany); Isao Nakamura (Japan); Thomas Rossing (U.S.A.); Julius O. Smith (U.S.A.)

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Contents

See also the abstracts of the Colloquium on Historical Musical Instrument Acoustics and Technology organised jointly by the Edinburgh University Collection of Historic Musical Instruments and the Galpin Society, to be held in Edinburgh 22-23 August 1997.


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Bowed String Instruments

1 

Bow Notes

Knut Guettler
Norwegian State Academy of Music, Oslo, Norway

Musicians and bow makers claim with great conviction that they are able to detect differences in timbre between bows. The same is claimed for differences in the playing characteristics. In the string player's repertoire of bowing styles, a variety of bow qualities are asked for, some of which may seem contradicting. In legato playing, for instance, the bow should be tranquil (at least in the bow-force plane normal to the string), ensuring a stable bow-string contact. In contrast: spiccato and ricochet bowing requires the bow to be vigorous in the same plane, facilitating rapid bounces on and off the string. The good bow is said to be capable of both.

Over the last few decades the study of the physics of the bow comprises research on: resonances, modal behavior and static deformation, properties of rosin, bow hair and the stick-slip mechanisms involved, and not of least importance: the bowing parameters utilized in professional playing. The effect of the bow on the string during stick, as linear coupled oscillators, seems formally well established, but a comprehensive model of the bow-string interaction includes several nonlinear elements, the effects of which are not equally well analysed. Although our knowledge about the bow has grown considerably during the last few years, much remains before the physicist can tell the bow maker and the musician in which properties the excellent bow deviates from the average.

11 

The Bouncing Bow - some Important Parameters

Anders Askenfelt
Department of Speech, Music and Hearing, Royal Institute of Technology, Stockholm, Sweden

Knut Guettler
Norwegian State Academy of Music, Oslo, Norway

The bouncing bow, as used in rapid spiccato and ricochet bowing, has been studied. Statical measurements of the compliance of the outer part of the stick were made by supporting the bow hair at selected points and loading the tip. The change in head angle was also estimated. Dynamical tests were made by monitoring the force history when the bow was dropped or played against a force transducer as a substitute to the string. The effect of displacing the point of percussion was studied by loading the stick with a mass at various positions. The action of the bow stick was investigated by comparing the performance of bows which were modified from the normal (concave) shape into straight sticks. Bows made of wood, fiber glass, and carbon fiber composites were studied and compared.

17 

Mobility at the Violin Bridge and Bridge Properties

Erik V. Jansson, Benedykt Niewczyk and Lars Frydén
Department of Speech, Music and Hearing, Royal Institute of Technology (KTH), Stockholm, Sweden

The frequency response measured at the violin bridge usually shows a broad hill between 2 and 3 kHz. The hill seems to be a major quality factor of a violin and we have named this hill "the bridge hill". The bridge hill is affected both by the resonance properties of the bridge and properties of the top plate. Large differences in bridge properties give large influence on tonal quality but minor influence on the bridge hill. Does this controversial result stem from time-limited properties displayed in the time history of the response but masked in the time averaged frequency response? Or, are the minor differences of the bridge hill sufficient for the large tonal quality differences perceived by hearing?

23 

Transient Response of the Violin Body when Impacted at the Bridge and at the Strings

Nils-Erik Molin, Staffan Schedin and Per Gren
Division of Experimental Mechanics, Luleå University of Technology, Sweden

Erik V. Jansson
Department of Speech, Music and Hearing, Royal Institute of Technology (KTH), Stockholm, Sweden
Earlier, transient propagating waves in a violin body was recorded using pulsed holographic interferometry, when the violin was impacted horizontally or vertically at the bridge top. The excitation resembles that of a single transient impact pulse from the bow string interaction, the step of the sawtooth shaped force at the bridge. The impact force generates propagating transient bending waves in the corpus. The measurements show how an initial force at the bridge top, via the bridge is transformed into a couple which generates two waves moving outward from the bridge feet, with different speed along and across the grains, as well as how energy is transmitted via the sound post to the back plate of the violin. These investigations were made with photographic film as recording media.

Recently, a pulsed TV-holography system has been developed which allows simpler and faster recording as well as quantitative evaluation, all electronically monitored. Experiments using this new system will be reported on, especially transient bending wave propagation in the violin body when strings are impacted by a pizzicato.

29 

Normal Modes of Vibrations in Violins

Mark Roberts and Thomas D. Rossing
Physics Department, Northern Illinois University, DeKalb, U.S.A.

A normal mode of vibration represents the motion of a linear system at a normal frequency (eigenfrequency). It should be possible to excite a normal mode of vibration at any point in a structure that is not a node and to observe motion at any other point that is not a node. The normal modes of vibration or eigenmodes of a violin are determined by the coupled motion of the top plate, back plate, enclosed air, ribs, neck, fingerboard, etc., a fact that is clouded a bit by designating modes as "air modes", "plate modes", etc. Using electronic TV holography we have studied the vibrational motion of several violins, one a Hutchins violin previously studied by other investigators, and we have attempted to reconcile some of the differences in the normal mode descriptions that appear in the literature. We compare the vibrational motion of the violin when it is excited by a force applied to the bridge and by an oscillating sound pressure (applied externally and internally).


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Bowed and Plucked String Instrumens

37 

The Physics of "Matching" Modes A0 and B0 in the Violin

James Woodhouse
University of Cambridge, U.K.

In recent years, success has been reported by Hutchins and others in improving the sound and/or playing properties of violins by adjusting the structure to "match" the frequencies of the modes A0 (modified Helmholtz air resonance) and B0 (lowest free-free bending-beam mode of the whole instrument). The changes in the coupled modes of vibration have been studied as a parameter (such as fingerboard length) is varied to take the instrument through the "tuned" condition. In fact "matching" is never achieved, since "curve-veering" behaviour is seen, as in many coupled vibrating systems. Measured data from a number of instruments will be used to support a simple model of the behaviour. The implications of such "mode matching" for violin makers and players will be explored.

43 

Measurement of Bow Force

Robert T. Schumacher and Stephen Garoff
Department of Physics, Carnegie Mellon University, Pittsburgh, U.S.A.

By using signals from force transducers at the terminations of a bowed string, it is possible to reconstruct the velocity of the string at the bowing point and the force exerted on the string by the bow in the plane of the string's motion. The theory of the reconstruction is presented, as well as some methods of realizing the theory in practice with sampled data. Examples using simulated data and data from a bowed E string are given.

49 

Evaluation of Acoustic Quality of Plucked Strings by means of Physical and Geometric Paramaeters

Edgar Lieber
Plauen, Germany

The theory of plucked stiff strings enables us to develop characteristics for the intensity of partials, inharmonicity, playing properties. This will be demonstrated for all six strings of the guitar. A comparsion with subjective impressions is explained. Inharmonicity has a big influence on the brilliance of tone. But there are complications which can modify subjective judgement:

  1. The longitudinal effect which can change timbre
  2. Inhomogeneities in diameter and density can spoil sound
  3. Players can limit the intensity of partials by "holding back"
  4. Interaction with corpus of the instrument by coupling over saddle and bridge

55 

The String-Finger Interaction in the Classical Guitar: Theoretical Model and Experiments

Maria Pavlidou and Bernard E. Richardson
Department of Physics and Astronomy, College of Cardiff, University of Wales, United Kingdom

The interaction which takes place between the string and the guitarist's finger influences the radiated sound of the instrument. In order to investigate how the physical properties of the string and fingertip affect the sound, a numerical model of the interaction has been created.

The model takes into account the propagation of transverse (in two planes) and torsional waves along the string during the interaction time, as well as the role of the frictional force between the fingernail and the string. The movement of the bridge is also included, allowing for information from the guitar body to come back along the string. The equations of motion are solved by using the finite-difference method. The model predicts the trajectory of the plucking position during and after the interaction as well as the movement of the whole string.

In order to validate the theoretical model, measurements of the string movement near the plucking position were made by using two optical sensors. The experimental set up traces the string shadow in two planes perpendicular to the string length during various plucks.

In the present work we describe the theoretical model, its predictions and compare the theory with the experimental results.

61 

Mental Modelling for Guitar Acoustics

Trevor Semple
London Guildhall University, London, U.K.

One of the greatest achievements of the human mind lies in our ability to manipulate complicated information by reducing it to a form that is easier to understand like graphs, symbols, diagrams, or pictures. When we are struggling to make sense of a new idea, the most valuable gift is a mental model. The art of mental modelling is to create a very clear, simple version of the problem by converting the abstract into the concrete.

Musical instruments are dynamic acoustic structures, allowing very open-ended design. An instrument is a hundred thousand details. For every one of these details, a decision is required about size or shape or position or material or adhesive, and so on. In making each decision, you can always ask: "what if ......?".

I use my own mental models in order to see more clearly how a guitar works like swimming pools, paddles and longbows. By their very nature these models are overviews and therefore incomplete, but this does not detract from their value. They can evolve allowing understanding to deepen and like a jigsaw puzzle, pieces begin to link up.


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Musical Instrument Materials

69 

Materials Selection for Musical Instruments

Claire Y. Barlow
Cambridge University Engineering Department, U.K.

This paper explores some ways in which materials may be selected for use in musical instruments. It is not intended as a comprehensive survey of instruments, materials needs, or available materials. The purpose is to demonstrate a powerful methodology, to introduce the idea of mechanical property maps of different classes of materials, and to touch on the importance of microstructure in selection of a material. Examples are used to illustrate how a materials database presented in the form of maps can be used to optimise the choice of material for chosen application.

Violins are made of wood. If a violin-shaped instrument were to be invented today, would wood be the obvious choice of material, given the huge range of artificial materials now available? A related question is to ask whether there are any reasonable substitute materials which could be used if good wood of a particular species became unavailable. These two questions could be tackled in two rather different ways. For 'reinventing' the violin one might try to analyse the mechanical properties of the materials required for such an object, and to optimise the material choice using some criterion. For finding wood-substitutes one might look for materials with the same range of properties as the wood which had become unavailable. We will discuss these and related problems, and begin to identify some criteria for the selection of appropriate materials.


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Keyboard String Instruments

79 

Grand Piano and Upright Piano: Differences in Sound and Radiation

Ingolf Bork
Physikalisch-Technische Bundesanstalt Braunschweig, Germany

For the pianists the preference for the grand piano compared with the upright piano is evident. Quality differences are ascribed not only to the sound but also to the mechanical behaviour of the action. The comparison of all acoustical and vibrational relevant parts reveals a lot of functional differences of the two piano models. Therefore various measurement were done to document the different properties, e.g. the sound field due to the different radiation position of the soundboards was investigated using modal analysis software. The aim of these investigations is to find the quality relevant parameters for the piano in general which may lead to improvements by better understanding the contribution of individual parts to sound quality.

85 

Tuning of FEM Models of Soundboards by the Results of Experimental Modal Analysis

Alois Raffaj
PETROF, Hradec Králové, Czech Republic

Specially orthotropic thin plates (half of guitar top plate) and generally orthotropic thin plates (upright piano soundboards) with free edges were analysed by experimental modal analysis (EMA). Specially orthotropic plates means that the grains run parallel with edges and generally ones means that grains are not parallel with edges. Modal frequencies and mode shapes of different ribless plates were obtained. The elastic constants EL, ER and GLR have been determined by resonant frequencies of the lowest bending (2-0,0-2) and twisting (1-1) modes. Poisson ratio was obtained after plate tuning to modes X and O. These elastic constants have been used as input parameters to FEM model of sounboards. FEM model was tuned by elastic constant variations to obtain good agreement with results of EMA. The reasons of discrepancies are analyzed. Some experiencies in ribs and boundary conditions modeling are presented.

91 

The Double-Pendulum Piano Action

A.Y. Gokhshtein
Russian Academy of Sciences, Moscow, Russia

In the traditional constructions of piano the disengagement of the hammer is kinematical: the spieler is removed before the key comes to the end position. The last quarter of the key shift forms the silence sone where the contact with the hammer is lost. The new approach proposed here makes the construction more simple and the control of the hammer movement more complete.

The essential element of the new grand piano action is the L-shaped inner pendulum which can rotate independently within the hammerstiel. The spieler engages the inner pendulum during all the stage of the key movement providing the hammer acceleration. At the next stage of free flying the inner pendulum rises together with the hammerstiel. After collision of the hammer with the piano string the hammer is repelled but the inner pendulum continues to move in the former direction and begins to rotate relative to the hammerstiel. This inertial movement disengages the hammerstiel which falls on the repetition spring and catches hold of the fanger. The next engagement of the hammer is happen at the reverse movement of the key and occurs by the gravity of the inner pendulum.

Such action gives the opportunity to achieve the better repetition and diversity of the piano sounds.

97 

Change in the Characteristics of Piano Tones under Different Concert Pitches

Tomoyasu Taguti and Osamu Tokuyama
Konan University, Higashinada, Kobe, Japan

Raising the concert pitch of a musical instrument, e.g., A4 tuned to 445Hz, is said to make the tones brighter, tenser, etc. This paper reports an acoustical measurement and a listening experiment on the tones of a piano where A4 is tuned to 436Hz(L:low), 442Hz(N:normal), and 445Hz(H:high). The result is summarized as follows:

  1. Physically, a clear distinction was found regarding the energy decay and the inharmonicity of single piano strings in that the former becomes faster, and the latter becomes decreased as the pitch is raised. (The latter is implied in fact by the formula of inharmonicity by Fletcher.) For key C3 as an example, the decay rates in dB/s were {-3.88(L), -4.00(N), and -4.43(H)}; and the inharmonicities in cents were {20(L), 17(N), 10(H)} at the 10th partial, and {45(L), 42(N), 35(H)} at the 20th partial.
  2. Subjectively, analysis by the method of paired comparison with thirteen adjectives, where the evaluation was made by nine subjects who were non-musicians, showed no significant distinction as a whole in the recorded sound materials L, N, and H (of single piano strings), as far as the reproducing pitches of these three were made equal. (The reproducing frequency of materials L was raised by a factor of 442/436, etc.)
Hence, the conclusion, though tentative, is that tuning a piano to different concert pitches only does not change the timbre effectively. A listening experiment with musically-trained subjects is under preparation.


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Stringed Instruments

101 

On the Kinetics of Spiccato Bowing

Knut Guettler
Norwegian State Academy of Music, Oslo, Norway

Anders Askenfelt
Department of Speech Communication and Music Acoustics, Royal Institute of Technology, Stockholm, Sweden

A skilled performer is able to play a series of spiccato strokes (i.e., producing short notes by means of a bouncing bow) with each onset showing little or no aperiodic motion before a regular slip/stick pattern (Helmholtz motion) is triggered. Kinematic analysis reveals that a well-behaving bow gives nearly vertical impacts on the string, and that each note's first release takes place when the normal bow force is near its maximum. The complex movement of the stick can be decomposed into a translational and a rotational motion. The translational movement starts with a straight-lined downward/backward shift (for down bow) and returns in the same path with an upward/forward shift for the next attack. Within this cycle, the bow describes two periods of rotational motion with the finger grip (thumb and the opposite fingers) near the axis of rotation. This paper discusses the relation between the quality of attacks and the phase relation between these two motions.

107 

Listeners' Judgements and Acoustic Properties of Violins

Georg Heike
Phonetics Institute, University of Cologne, Germany

Selected violins with different frequency curves and presumably different sound properties were submitted to listening tests. The violins were played in pairs; listeners were asked to decide which violin of each pair they preferred in terms of "tonal quality" ("Klangqualität") and "carrying power" ("Trägfähigkeit"); no definitions of these categories were offered.

On the whole, preliminary results indicate a good correlation between listeners' judgements and frequency curves: violins with poor frequency curves received unfavourable judgements. Within the group of preferred instruments, however, evaluation in terms of tonal quality differed considerably from evaluation in terms of carrying power; judgements seem to depend on the violinist and on the player-to-listener distance. Results also suggest that the category "carrying power" combines two qualities: (1) maintenance of tonal quality over a great distance; (2) loudness (or dominance) in relation to noise (accompaniment). The correlation of carrying power with an overtone region equivalent to the singer's formant does not seem to be as direct and simple as has been supposed. Further results will be presented in detail.

113 

Friction, Damping and Bowed String Pitch and Timbre

Alison J. McMillan
Newcastle under Lyme, Staffordshire, U.K.

Any analysis of the physics of bowed string dymanics must consider in detail the nature of the friction between bow and string. For example, the simplest model of friction in which the opposing force is independent of the sliding speed, will predict steady slip rather than self-excited vibrations. The friction law is thus critical to a realistic model of the bowed string. An empirical friction law is proposed which is a function of both sliding velocity and acceleration. The effect of this law in the generation of self-excited vibrations is demonstrated for a single degree of freedom (spring-mass-damper) system with various levels of damping. This suggests that, for sufficiently energetic excitation, vibration rather than steady slip will occur, even for highly damped systems. The argument is extended to multi degree of freedom systems (bowed string) to analyse the effect of modal damping and friction law on the relative excitation of modes, and thence to decribe the influence of bowing conditions on timbre.

119 

Bowed String Instruments: F Holes and Bass Bar Effects on Plate Tuning

Anne Houssay
Drancy France

While making the back and belly of an instrument of the violin family, can the maker anticipate what tuning is to be obtained on the finished front ?

Traditionnally, one does not retouch from the inside the thicknesses of the table after the f holes and bass bar are done, in order to obtain the nice smooth and regular internal curve that is usually aimed for. That is why the maker must know in advance the effects the cutting of holes and the addition of bar will have on the frequencies of modes, in order to achieve the final tuning he wishes, between the modes of the front and with those of the back.

In this study, measuring the frequencies has been used as a tool to guide the working process of the next instruments beeing built. In that way, 3 violins, 4 violas and 3 cellos were measured during their making between 1985 and 1990, with a very simple equipment (frequency generator, high speaker and powdered sugar), thanks to Carleen Hutchins's directions given in CAS NL #39, 1983.

Some conclusions are given on the influence of f holes (position, shape and cutting) as well as of the bass bar (gluing and shaping) on the tuning of the instrument's table.

125 

Violin Tones Spectra and their Relationship to Perceived Sound Quality

J. Stepanek, Z. Otcenasek, V. Syrovy
Music Faculty, Academy of Performing Arts, Prague, Czech Republic

A. Melka
Acoustics Prague, Prague, Czech Republic

The perceived sound quality of violins was studied on five different tones. Tones of 24 instruments representing a large extent of instrument quality, played non vibrato, were recorded. Eleven sound recordings for every particular tone were successively selected for perceived sound quality preference tests. Comparing the judgements of ten evaluators for every particular tone, relative group preferences were calculated, and the rank of instruments according to their perceived sound quality was set up. The harmonic spectra were computed using the sustain parts of the sounds. By comparing the results for every particular tone, it was possible to better ascertain the frequency position of the formant regions of violin tones. The relationship of perceived sound quality and the levels of individual harmonics and the other spectral characteristics was treated using the correlation analysis. Finally, properties of sustain spectra found in quality violin tones are discussed.

131 

Starting Transients in Violins and the Elusive Body Resonance C3

Erik V. Jansson and Anders Askenfelt
Department of Speech, Music and Hearing, Royal Institute of Technology, Stockholm, Sweden

A body mode (C3) of the violin at about 550 - 600 Hz shows intriguing behaviour. Being close in frequency to the first top plate resonance (T1) at about 450 - 500 Hz, a confusion has sometimes occurred in the identification of these modes. A pronounced C3-resonance seems to be a characteristic of high-quality instruments with low arching. The relation between the levels of T1 and C3-peaks in the input admittance is highly sensitive to the position of the soundpost. The sound radiation at the frequency of the C3-resonance is omni-directional. Experiments, measuring the bridge motion and radiated sound, showed that for vigorous bowing (detaché, martellato), a strong C3-component is present in the initial part of the tone before the string partials have developed.

137 

Measuring the Physical Characteristics of Violin Bows

John S. Lamancusa
Department of Mechanical Engineering, Penn State University, University Park, Pennsylvania, U.S.A.

The violin bow is a critical and often-neglected element in the production of good violin tone. The bow maker makes various decisions in selecting the pernambuco blank (density, elastic modulus), graduation and camber of the stick. These decisions determine the static properties of the bow (center of gravity, moment of inertia, stiffness distribution) as well as its dynamic properties (natural frequencies, mode shapes, and damping). These physical determine the complex interaction between the bow hair and the string and give each bow its own "signature" sound and feel.

This paper addresses the static characteristics of violin bows and their correlation to player's impressions of tone and playing qualities. Methods for measuring the static properties of bows are reviewed. A common measure of bow stiffness is to support the stick at its ends and apply a one pound load to the center of the bow and measure the deflection at the same point. However, this measure does not necessarily correlate to the player's subjective feeling of stiffness. Alternative methods for measuring stiffness and its distribution along the length of the bow are examined. Measurements and player's impressions of a number of fine violin bows are presented.

143 

Material Dependence of the Vibrational Behaviour of the Guitar's Plate

A. Ezcurra
Dpto. de Fisica - Universidad Pública de Navarra, Pamplona, Spain

M.J. Elejabarrieta
Dpto. de Fisica Aplicada II, Universidad del Pais Vasco Bilbao, Spain

Nowadays classical guitars must comply with some requirements: high level of sound, homogeneous response in the low and high frequency range and a neat and warm timbre. Moreover, it is well-known that the plate is the most relevant part of the complete guitar since it determines the response of the resonance box, and in consequence of the whole instrument. Taking this into account we present a detailed study of the vibrational properties of the guitar's plate, that can be studied by analysing the vibrational behaviour, that is, normal modes and frequencies, admittance curves and quality factors of the bare plate, and the influence on this behaviour of the additional internal structures. With this aim in view we have focused our attention to the first task, doing a comparative study of the three most common types of wood used by craftsmen for guitar plates: cedar, spruce and 3-ply wood by means of the modal analysis technique, getting their characteristics and discussing the influence of these characteristics on the quality of the final instrument.

149 

On the Relationships between the Response of the Guitar Body and the Instrument's Tone Quality

Howard Wright and Bernard E. Richardson
Department of Physics and Astronomy, College of Cardiff, University of Wales, United Kingdom

Psychoacoustical work is presented which uses sounds synthesised from a numerical model of the guitar to examine the links between the physical properties of the instrument's body and aspects of the guitar's tone quality. The response of the guitar body is described in terms of its normal modes, each mode being characterised by four parameters: a resonance frequency, a Q-value, an effective mass and an effective monopole area. The sound pressure response of the instrument is calculated for a given plucking force applied to one of its strings. Alterations to the body-mode parameters affect the coupling between the string and body, causing the radiated sound to change. The differences in tone quality that result from changes to individual body-mode parameters are investigated in a number of psychoacoustical listening tests. The results indicate that alterations to the effective masses and areas of the body modes have a greater effect on the instrument's tone quality than changes to the mode frequencies. Furthermore, the effective masses and areas have a "global" influence on tone, in which notes with fundamentals covering a wide range of frequencies are affected.

155 

Holographic Studies of Cello Vibrations

Eric Bynum and Thomas D. Rossing
Physics Department, Northern Illinois University, DeKalb, U.S.A.

The principal modes of vibration observed in the body of a cello show some similarities to those observed in violins. The lowest sound-radiating mode at 102 Hz is quite similar to the so-called A0 mode in violins, and a mode at 144 Hz is characterized by strong motion in the top plate, similar to the T1 mode in violins. A mainly torsional mode of the body (similar to the C2 mode inviolins) occurs around 170 Hz, and a "ring" mode (like the C4 mode in violins) occurs around 190 Hz. A strong mode at 220 Hz appears to be similar to the strongly-radiating C3 body mode in violins. Modal frequencies in this cello occur at about 0.29 to 0.43 times the corresponding mode frequencies in violins,which puts them in slightly different relationships to the open string frequencies, which are 0.33 times those of a violin.

 

The Problem with Veneers on Harps: Practical and Theoretical Considerations

Alexander Bell and Sarah Charlesworth
Centre for Combined Studies, Heriot-Watt University, Edinburgh, U.K.

The concert harp is unusual amongst musical instruments in that the wood grain of the soundboard lies across the board. Many makers fix a thin wooden veneer to the board: its grain is along the soundboard and it is a very decorative feature. The acoustic effect of the veneer is detrimental. There are predictable changes to density and effective Young's modulus, but the Q-values of any resonances fall. We will present experimental details of testing on sample spruce bars, and link this to Finite Element analysis of the problem. With any luck, the FE analysis and the experimental results will be in accord.

163 

Two Dimensional Measurement of a Piano String Vibration

Keinosuke Nagai, Hideyuki Tanaka and Koichi Mizutani
Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan

Equipment has been made to measure the two dimensional motion of the piano string E1. It has been found:

  1. The piano sound is formed by the coupling of the vertical and horizontal vibrations, which occurs at the inclined pins of the bridge.
  2. The string vibrates at first vertically to the soundboard and then it starts to rotate. The direction of the rotation changes alternately every about six seconds.
  3. The first direction of the rotation is not determined. It depends on how to touch the key.
  4. The vertical vibration attenuates rapidly, while the horizontal one keeps almost same level. This may cause the two rate of a piano-string-decay.

169 

Fat Strings

Douglas Nunn
Durham University, U.K.

The classical analysis of a vibrating string assumes that the string is perfectly flexible. This implies that the partials will be harmonically related. In practice, however, the finite stiffness of real strings means that the partials become sharper with increasing frequency.

This paper examines an extreme case of frequency stretching in which the second partial falls at three times the fundamental frequency. This vibrating system can be thought of as intermediate between a string and a bar, and might be expected to have an intermediate timbre. This can be made using a "fat string", much thicker and shorter than that for a near-harmonic string.

I start by giving a theoretical overview of frequency stretching and inharmonicity, and derive the dimensions required for fat strings. I then give synthetic examples of the timbres available. Finally I discuss practical considerations in designing instruments using fat strings, and present prototype instruments using these principles.

175 

Modal Analysis of an Upright Piano and its Case

Taro Mori and Ingolf Bork
Physikalisch-Technische Bundesanstalt Braunschweig, Germany

When an upright piano is played, not only the sound board is set into vibrations. Touching the surface of other parts like the cover gives the feeling of the vibration which of course may contribute partially to the sound field. Therefore it is reasonable to assume that the whole system simultaneously takes part in the radiation process. In order to estimate relative vibration amplitudes of individual components the whole upright piano including its case was measured by modal analysis. While it is known that investigation of the sound board vibrations enables to determine the characteristics of the piano sound, the piano case, especially the upper panel and the cover can also have influences, because they exist directly between the player and the sound board. It will be shown in how far the resonances change the sound and the decay process of piano tones.


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Percussion

181 

Active Control of Timbre Radiated by a Fluid-Loaded Percussion Instrument

Douglas Rollow, David C. Swanson, and Courtney B. Burroughs
Graduate Program in Acoustics, Pennsylvania State University, U.S.A.

Conventional membranophones radiate sound according to the influence of the surrounding fluid medium (air) as well as the mechanical parameters of the membrane and the supporting structure. In this work, an active control system which affects the vibration of individual modes of the drum head is described, and the behavior of the resulting electromechanical system is shown. The timbre of the system can be modified by changing the operation of the control system, resulting in a drum which can produce a variety of sounds not available with strictly mechanical systems.

The instrument consists of a Mylar timpano head stretched over an enclosure which has been outfitted with electroacoustic drivers. Sensors are arranged on the surface of the drum head so the motion of individual modes can be determined, and the array of drivers allows independent control of these modes. A multichannel digital signal processor is used to implement the control filters. By modifying the loading of each mode, the timbre of the radiated sound is changed as the decaying spectrum varies. In addition, the spatially distributed sensors can allow a musician to use new expressive techniques not found in traditional instruments.

Work supported by the Exploratory and Foundational fund, Applied Research Laboratory.

195 

Measurement of Performance Responses Differences using Straight and Bent Tube Marimba Resonators

Barry J. Larkin
Department of Music, Iowa State University, Ames, USA

Ronald A. Roberts
Aerospace Engineering and Engineering Mechanics, Iowa State University, Ames, USA

In recent years, the range of concert marimba instruments has extended from the standard four octave instrument to instruments reaching five octaves and beyond. When constructing such an instrument, the resonator lengths of the lower pitches present problems of design. The length of pipe needed to resonate pitches in the lower octaves are usually longer than the height of the instrument. Designers, dealing with these lower pitches, are required to bend the pipes in various configurations in order to accommodate the additional length. Marimba performers debate how the pitch and color of the resonated note is influenced by these various configurations. Experiments are being performed with the pitch great F sharp (Fsharp2) to determine if any such difference can be detected in laboratory measurements between a resonator that has been soldered with two forty five degree pieces to accommodate the necessary bending and a identical resonator that straight. This paper will outline experimental techniques used in recording airborne responses generated by repeated mallet strokes in the recital hall at the Iowa State University Department of Music. Data analysis will be summarized, and results will be presented showing the nature of measured differences in both overtone structure and response evolution.

201 

Transient Wave Propagation in a Cymbal

Staffan Schedin and Per O. Gren
Division of Experimental Mechanics, Luleå University of Technology, Sweden

Thomas D. Rossing
Physics Department, Northern Illinois University, DeKalb, U.S.A.

Using an electronic system for pulsed TV holography with a double-pulsed ruby laser, transient wave propagation during intervals from 30 to 480 microseconds after impact is recorded. The first observable bending waves, having wavelengths of about 5 mm, propagate at about 1700 m/s and reach the edge of the cymbal in about 60 microseconds. These are quickly followed by waves of longer wavelength which scatter at the outer edge of the cymbal and also the dome and result in standing waves. A phase unwrapping procedure is used to obtain a three-dimensional map of the wave field. Holographic film recordings similarly show scattering of transient bending waves at the central dome.

207 

The Effects of a Resonator Tube on the Timbre and Directivity of a Vibrating Bar

Brian C. Tuttle and Courtney B. Burroughs
Graduate Program in Acoustics, The Pennsylvania State University, U.S.A.
A common method of amplifying the sound produced by a bar percussion instrument is to place each bar directly above a resonator tube tuned to one quarter wavelength of the bar's fundamental frequency. This research explores the changes in timbre and directivity produced when a resonating structure is placed near a vibrating bar. These changes are observed through measurement of an aluminum bar and resonator tube from a vibraphone and by a computer model of the system.

Both nearfield and farfield measurements are made of the frequency spectra and directivity of the bar with and without the resonator tube. The surface velocity of the bar is measured with laser vibrometry to show the dominant modes of vibration. The system is modeled computationally using a finite element method for the structural vibrations of the bar and a boundary element method to show the sound radiated from the bar and resonator tube. With this computational method, different shapes and positions of the resonating structure may be modeled, and the resulting changes in timbre and directivity may be observed.


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Stringed Instrument Simulations

213 

Calibration of Physical Models Using Artificial Neural Networks with Application to Plucked String Instruments

Ali Taylan Cemgil
Department of Computer Engineering, Bogazici University, Istanbul, Turkey

Cumhur Erkut
Department of Electronic and Communication Engineering, Yildiz Technical University, Istanbul, Turkey

Over the last decade, physical models of plucked string instruments are examined and applied to real time sound synthesis with success. This extensive work offered various parametric and nonparametric methods to estimate model parameters, and the calibrated models produced useful results. However, many methods use simplified acoustical or psychoacoustical aspects of musical sounds for the sake of simplicity.

This study introduces an artificial neural network (ANN) based scheme to estimate the model parameters for plucked string instruments. The system consists of a preprocessor and an ANN model. The preprocessor computes the time-varying spectral contents of recorded sounds and this data is fed into the ANN model to implement the nonlinear mapping to the parameter space. With an intermediate bark filter block between the preprocessor and the ANN model, the perceptual properties of the auditory system can be incorporated in a straightforward manner. Three different ANN topologies are compared, a multilayer perceptron (MLP), a time-delay neural network (TDNN) and a Self Organizing Map (SOM). Various plucked string models are calibrated using this scheme, and the results are compared with other methods.

219 

A Physical Model of Stiff Strings

Italo Testa, Sergio Cavaliere and Gianpaolo Evangelista
Department of Physical Sciences, University "Federico II", Naples, Italy

The digital waveguide approach to the synthesis of musical instruments is receiving an increasing interest, due to the direct physical interpretation of parameters and good acoustic performance.

In this paper, we generalise the Karplus-Strong algorithm in order to accurately model dispersion due to stiffness and air friction. It will be shown that the equation of a stiff string in continuous time domain, again leads, in discrete space and time domain, to a digital waveguide model consisting of a chain of all-pass filters.

Starting from the solution of the equation, an analytic expression of a delay term is obtained, which depends on the frequency and on the physical constants of the system, such as inertia moment, Young modulus and transversal velocity. This term is approximated by the phase of an all-pass filter whose coefficients are calculated by means of an error minimisation algorithm. As in the non-dispersive case, the delay line is fed back by a loop filter, whose action is a frequency dependent attenuation in time of the signal travelling on the string.

This approach is particularly attractive for the synthesis of low octave piano strings. However, it can be extended to synthesise other percussive instruments such as drums, membranes and plates, for which stiffness is extremely relevant from an acoustical point of view.

225 

Numerical Simulations of Stringed Instruments: Modeling of String-Plate and Plate-Cavity Coupling

Christophe Lambourg, Mathieu Huet and Antoine Chaigne
ENST, Departement SIGNAL, CNRS URA 820, Paris, France

This paper is the direct continuation of previously presented models of rectangular isotropic and orthotropic vibrating plates [1][2]. The modeling of the damped plate is now extended by taking its interaction with both strings and closed cavity into account. Finite-difference methods are used for solving numerically the partial differential equations of the problem in the time-domain. The set of equations to be solved is now made of the association of:

At the present state-of-the-art, the reaction of the exterior acoustic field on the plate is neglected. In addition, the cavity is assumed to be perfectly closed, with no holes in the plate. The stability condition of the numerical algorithms is obtained through energetic methods. From a physical point of view, the investigation of the variations of energy with time yields interesting informations on the energy transfer between plate and cavity.

The numerical results are compared with analytical solutions, in simplified situations. The model is used also for exploring the influence of the geometries of both plate and cavity on the modal coupling and time-evolution of the sounds. Particular attention is paid to the sound pressure inside the cavity.

References

  1. Christophe Lambourg & Antoine Chaigne, Time-domain simulation of vibrating plates: preliminary results, Proceedings of the International Symposium on Musical Acoustics, Dourdan, 1995, 358-365.
  2. Antoine Chaigne & Christophe Lambourg, New developments in time-domain modeling of plates for the simulation of string instruments, Third Joint ASA-ASJ Meeting, Honolulu, 1996.

231 

Comparison of String Vibration Spectra Excited by a Different Piano Hammers

Anatoli Stulov
Department of Mechanics and Applied Mathematics, Institute of Cybernetics, Tallinn, Estonia

The process of a flexible string excitation by striking with a piano hammer is considered. Two models of the piano hammers were used for comparison. The first model considered is the usual model that connected the force acting on the hammer with the felt compression by a power-law dependence. The second model of the hammer considered is the hysteretic model published in J. Acoust. Soc. Am. v.97, 2577-2585 (1995). This model of the hammer describes the real piano hammer better, and takes into account the hysteresis-type of the force-compression characteristics of the felt deformation also.

The flexible string obeys the wave equation that is satisfied by simple nondispersive waves represented by a combination of arbitrary waveforms moving along the string in the opposite directions from the striking point.

The results of numerical calculations of the hammer-string interaction are presented in the form of the force histories and the string vibration spectra for hysteretic and nonhysteretic hammers for comparison. The comparison of the numerical model results with the measurements is also presented. It is shown that the hysteretic model of the hammer gives prediction of the string vibration spectrum better than the nonhysteretic one, and without allowing for additional physical processes in the string as damping.

239 

Parameter Synthesis of Quality Piano Tones in Real Time using Programmable Digital Signal Processors

Paul A. Wheeler and David H. Woodcox
Electrical and Computer Engineering Department, Utah State University, Logan, U.S.A.

The Strong-Barlow Model used to synthesize the vibrational characteristics of the piano timbre was developed at Brigham Young University. Although the model was well defined, the parameter values needed to create individual piano notes had not been determined. This paper reports research performed at Utah State University using this model. A method was developed to extract synthesis parameters from recorded piano tones. This method examined the behavior of the spectrum of a note as a function of time and computed values for frequency, decay-factor, and scale-factor used in the model. The model used these parameters to compute output values that were written into an industry standard audio file for convenient playback. Once the piano tone synthesis parameters were derived, a real-time implementation using programmable digital signal processors was proposed. This research demonstrated that quality piano tones could be generated with this model. A real-time system was realizable using current digital signal processor technology.

245 

Automated Parameter Extraction for Plucked String Synthesis

Tero Tolonen, Vesa Välimäki and Matti Karjalainen
Laboratory of Acoustics and Audio Signal Processing, Helsinki University of Technology, Espoo, Finland

We present an improved analysis technique for physical modeling of plucked string instruments and excitation with wavetables. The estimation procedure is automated to obtain accurate and reliable parameters for a new multirate synthesis model.

Multirate DSP techniques are used to reduce memory requirements and computational burden. These techniques include modeling the decay part of the synthesized signal at a lower sampling rate. Also the lowest body resonances are modeled with separate filters using a low sampling rate. With these methods the excitation wavetables will require less memory.

An analysis technique using the short-time Fourier transform has been proposed before. This technique is developed further and a new method for computation of the excitation signal is proposed. This method uses spectral modeling synthesis techniques to inverse filter the original signal in the frequency domain. An optimal solution for the loop filter design is found by introducing an error weighting function which takes into account the behavior of each individual harmonic. The automatic detection and extraction of body resonances is also demonstrated.

The MATLAB files implementing the proposed analysis method will be available via FTP. Sound examples of resynthesis of guitar tones will be played at the ISMA'97.


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Simulations of Wind Instruments

251 

Time-domain Modeling and Computer Simulation of an Organ Flue Pipe

Seiji Adachi
ATR Human Information Processing Research Laboratories, Kyoto, Japan

Woodwind instruments having no physical vibrating reeds, such as flutes, recorders and organ flue pipes, are called air-jet driven instruments. Despite the simple structure, interaction between an air jet and the acoustic excitation at the pipe mouth is complex. Therefore, the sound production has not yet been fully understood. Jet deflection models proposed so far are somewhat hypothetical and empirical, and are not derived from the first principle of the fluid dynamics.

Originally, the jet deflection has been considered in the frequency domain. This is because the interaction between the jet and the acoustic excitation is, at least approximately, linear. However, non-linear dynamics of the total sound production system makes it difficult to estimate exact behavior of the instruments such as the mode transition and the harmonic structures of produced sound. Time-domain description of the jet deflection and other part of the sound production process has an advantage to do such estimation.

This study presents a time-domain modeling of an organ flue pipe, and estimates the performances of jet deflection models proposed by several authors. They are also compared with the mode transition observed in an experiment of a pipe artificially blown.


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Reed Instruments

261 

Interactions of Both Reeds in a Channel of a Diatonic Harmonica

Laurent Millot, Christian Cuesta and Claude Valette
Laboratoire d'Acoustique Musicale, Université Paris, France

This works keeps up with the study of the diatonic harmonica which began at the MAL (Laboratoire d'Acoustique Musicale) from Paris, with the visit of the harmonicist J. Hanriot.

In oder to be able to explain the advanced modes (bends, overblows and overdraws) we introduce the buccal cavity in our modelling as an Helmholtz resonator. For each reed of a chosen channel, we carry out the calculation of the upwards acoustical admittance, which takes account on the one hand of the buccal cavity and on the other hand of the interaction between both reeds. As the two reeds are supposed to be in parallel, from the acoustical point of view, for the chosen channel, the total acoustical admittance is the sum of both reeds admittances. With this modelling, each mode, normal or advanced, is understandable but because we are not aware of the flow distribution through the reeds, we arrive at the multiplicity of the possible solutions : cases where auto-oscillation and so sound production are possible.

267 

Why is a Saxophone Louder than a Clarinet

Jean-Pierre Dalmont [1] and Kees Nederveen [2]
1. Institut d'Acoustique et de Mécanique (LAUM, UMR CNRS 6613) Av. O. Messiaen, BP 535, 72017 Le Mans Cedex, France
2. Pijnacker, The Netherlands

There is a great loudness difference between a clarinet and a saxophone. Even the saxophone closest resembling the clarinet in frequency range, the sopranino, is approximately 10dB louder than the clarinet, while blowing pressure, reed and reed slit are near the same for both instruments. Three causes can be considered:

  1. The clarinet reed is open half of the time, whereas the saxophone reed is open, depending on which note, up to 80% of the time; so the input power signal is larger for a saxophone
  2. As the asymmetric signal contains more higher harmonics, the radiation efficiency will be higher
  3. The difference in hole shape causes a difference in non-linear losses at the holes
To establish the contribution of each of these effects, experiments were carried out on an artificial blowing machine, the same mouthpiece being used for both instruments. At various places, in the mouthpiece, in the bore and outside the instruments pressures were measured to establish the transfer of energy from mouth to surroundings. Results will be compared with theoretical expectations.

273 

Blowing Pressures in Reed Woodwinds

Leonardo Fuks and Johan Sundberg
Music Acoustics PhD Programme, Royal Institute of Technology, Stockholm, Sweden

Blowing pressures in reed woodwind instruments, which range between 10 and 120 cm H2O, have been a matter of interest in some earlier investigations, aiming at different targets. In music acoustics, pressure data are required for comprehension of how the system consisting of player/instrument converts aerodynamic energy into sound. The complex relationship between input parameters (mouth pressure, air flow and the embouchure) and the resulting sound properties (pitch variations, loudness and sound quality) represent a challenging and promising issue in the physics of instruments. In musical practice and education, the mouth pressure data could be used to the identification of performance problems and to the development of methods that would make available better blowing control by the player.

Initially, the problem was addressed by means of aerodynamic and acoustic concepts and formulations. Then, blowing pressures were measured in the mouth cavity of players of each of four reed woodwinds, Bb clarinet, alto saxophone, oboe, and bassoon. The players performed tasks which consisted of sustained tones and arpeggio tones at four different dynamic levels and at pitches covering the normal range of the instruments. The results show that, within instruments, the players' pressures exhibit similar dependencies of pitch and dynamic levels. Between instruments, clear differences were found with regard to both pressure ranges and dependence on pitch.

279 

An Experimental Bassoon

Edgar Brown
Department of Physics, King's College, London, U.K.

The bassoon, more so than any other woodwind instrument, suffers from problems of intonation and variability of tone quality from note to note. Many attempts have been made to re-model the bassoon so as to mitigate these defects. All have failed in some degree to preserve the bassoon's highly-regarded tonal personality.

A renewed attempt has been made to address this problem. Following a programme of experimental work, an instrument has been built and will be demonstrated. The tone-hole layout has been chosen to improve tonal uniformity and intonation. By attention to the tone-holes lattice cut-off frequency and other design factors, an attempt has been made to preseve the tone-quality of the German-style instrument. A new key system, making use of the "universal sharp" principle has been used, although this is not an essential feature of the acoustic design.


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Flutes and Organ Pipes

285 

Effect of Voicing Steps on the Stationary Spectrum and Attack Transient of a Flue Organ Pipe

J. Angster [1], G. Paál [2], W. Garen [2] and A. Miklós [1]
1. Fraunhofer-Institut für Bauphysik, Stuttgart, Germany
2. Fachhochschule Ostfriesland, Emden, Germany

Stationary sound spectra and attack transients of a flue organ pipe (Diapason 4ft F) have been measured at every step of the voicing process. The adjustments have been carried out in situ by a professional organ builder. Qualitative estimates of the changes of the acoustic and flow parameters at the mouth due to the adjustment steps have been given using the results of recent LDA (Laser Doppler Anemometry), flow visualisation and flat water tank modelling experiments. The observed changes in the acoustic spectra and attack transients are analysed and compared to the expectations based on the predicted effects of the adjustment steps on the sound. In parallel, changes in the sound character are demonstrated using simultaneous DAT recording of the measuring microphone signal. Finally, the influence of the applied voicing steps on both of the stationary spectrum and the time evolution of the harmonic components during the attack are discussed in details.

295 

Sound and Flow at the Mouth of Flue Organ Pipes, Part 1: Fully Developed State

G. Paál [1], J. Angster [2], W. Garen [1] and & A. Miklós [2]
1. Fachhochschule Ostfriesland, Emden, Germany
2. Fraunhofer Institut für Bauphysik, Stuttgart, Germany

The absence of precise and detailed measurements of the flow characteristics within the mouth hampered the better understanding of the sound production mechanism of flue organ pipes which has been the subject of controversy for the last century. Non-intrusive optical methods (flow visualization and LDA) have been applied to the study of the plane jet swinging across the mouth which allow a significant improvement in precision and resolution. The fluid mechanical investigations were supplemented by acoustical experiments. The measurements have been carried out on two real metallic pipes: one open and the other stopped. Typical photos of the flow visualization at preselected phases of the sound period are presented as well as a video movie. Phase resolved velocity measurements are also shown in the form of a whole field streamline pattern. Relationships with acoustical properties are analysed. Differences between the various pipe types as well as between various voicing stages are discussed.

303 

Sound Intensity Measurements of an Open Organ Pipe

Anna Runnemalm
Experimental Mechanics, Luleå University of Technology, Sweden

Örjan Johansson
Environment Technology, Luleå University of Technology, Sweden

What part of an open organ pipe emits most of the sound and what is the spatial sound distribution for the harmonic tones? The sound intensity from a blown open organ pipe, tuned to C4 at 260 Hz, is measured in an anechoic room using a 3D sound intensity probe. The measurements are performed both in the vertical and in the horizontal plane in front of the pipe. The two dimensional sound intensity vector field for different harmonic tones are studied. The study focuses on the active mean intensity field and the results point out the main sources of acoustic power and their contribution to the far field. Pipes made of different material and tooled in different ways are compared. Interference phenomena between sources are also visualised. First it can be noted that the top and the mouth are the main sound radiators compared to the walls. They are of about the same strength for the first four harmonics. For the fifth and sixth harmonics the top is the main sound radiator. For odd numbered harmonic tones the mouth and the top emit sound in phase and for even numbers, out of phase. The material choice and tooling method affect the sound spectra.

309 

Looking for a New Design of Chimney Flutes

A. Hirschberg [1], A.P.J. Wijnands [1] and M.P. Verge [2]
1. Department of Physics, Eindhoven University of Technology, The Netherlands.
2. Laboratoire d'Acoustique Musicale, Universite Paris VI, France

Assuming that a chimney flue organ-pipe should have a strong fifth harmonic, we consider the design of such pipes. We propose a non-conventional position of the chimney with respect to the cap: half inside the pipe and half outside the pipe. This design is supported by calculations of the pipe admitance. Measurements of steady sound production and of the attack transient are presented for pipes obtained by modification of existing pipes from two different manifacturers. In particular we investigate the influence of the ratio of the chimney diameter to its length. We also investigated the influence of small variations in cap position for tuning purposes.

In order to gain insight into the influence of changes in the geometry of the mouth we carry out some flow visualization experiments on a small pipe. We compare those data to results obtained with a time domain simulation of the pipe response. The critical problem in this model is the description of the turbulent jet. We compare various existing models for the turbulent jet.

314 

The Acoustic Impedance of the Boehm Flute: Standard and some Non-Standard Fingerings

John Smith, Nathalie Henrich and Joe Wolfe
School of Physics, University of New South Wales, Sydney, Australia

The acoustic impedance Z(f) of the flute has a range of around 70 dB. We report the use of a novel impedance spectrometer [1,2] to measure the acoustic impedance of the flute with a resolution of +/- 1 1 Hz, a dynamic range of over 80 dB and which makes the measurement in 1 second. We report Z(f) for the standard fingerings over the range C4 to C7, and for selected non-standard fingerings as well. These results explain some of the idiosyncracies of the instrument well known to flutists, and in some cases suggest ways in which these may be overcome.

  1. Wolfe, J., Smith, J., Brielbeck, G. and Stocker, F. (1995) A system for real time measurement of acoustic transfer functions. Acoustics Australia, 23, 19-20.
  2. Wolfe, J. and Smith, J. (1995) A comparison of acoustic impedances of flutes - a preliminary study. Proc. International Symposium on Musical Acoustics, Dourdan, France. 100-106.


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Wind Instruments and Simulations

 

Optical techniques for measuring sound and flow fields in musical instrument research

C.A. Greated, D.B. Hann and D. Murray Campbell
Department of Physics and Astronomy, The University of Edinburgh, U.K.

In recent years there has been an increasing interest in the use of optical methods for the study of sound and flow fields in musical instrument research. Specific examples of their application are in the study of flow patterns in organ pipes and flutes. The two most important techniques are Laser Doppler Anemometry (LDA) and Particle Image Velocimetry (PIV). Both of these have been used extensively over a number of years for the measurement of flow velocities but only fairly recently has it has been recognised that they can also be used for sound measurement. LDA is a point measuring technique which can be used to simultaneously record the instantaneous flow rate and acoustic particle velocity. PIV is a whole field technique which can produce maps of flow velocity and acoustic particle amplitude.

The paper discusses the merits and limitations of these two methods as they apply to the study of flow patterns and sound levels in the bores and mouthpieces of woodwind and brass instruments and examples will be given of their application.

321 

Simulations of an Organ Flue Pipe Using an Empirical Jet Deflection Model

Seiji Adachi and Masa-aki Sato
ATR Human Information Processing Research Laboratories, Kyoto, Japan

Jet deflection mechanism is a central question of the sound production in air-jet driven instruments. Coltman [J. Acoust. Soc. Am. 60, 725-733 (1976)] experimentally determined phase of wave propagation on an jet relative to the driving acoustical field. In this paper, we carry out simulations of an organ flue pipe, using a time-domain description of the jet deflection deduced from his experiment. By changing the static pressure supplied to the pipe foot from 32 Pa to 10 kPa, we obtain various self-excited oscillations. The fundamental frequency and harmonic levels of the simulated sound are drawn in a mode transition diagram. We find that, in addition to the normal oscillation regime, underblows and overblows are generated. Overlaps of adjacent oscillation regimes, which indicates hysteresis in the mode transition, are observed. By comparing the diagram with the one experimentally observed, the jet deflection mechanism is discussed. Our preliminary measurements of the jet deflection is also presented.

327 

Simple Measurements ofthe Sound Pressure Levels of Pipe Organs

J.R. Oswin
BAeSEMA Ltd, Bristol, U.K.

G.A.A. Rock
Graham Rock Acoustics, Taunton, U.K.

Whereas papers on the tonal quality of organ pipes and the influences on tone generation are well represented in the literature, data on the sound levels produced are scarce.

This paper presents measurements made with a simple hand-held meter on a number of instruments. These span the range of small-to-medium size instruments most commonly found, rather than the larger, more spectacular organs.

Even small organs present the opportunity for large numbers of measurements which can lead to unmanageable data sets which defy classification and comparison, so a measurement set is developed which provides sufficient information over the frequency and sound power range of the instruments to help with a greater understanding of organ and building acoustics. This initial data base may prove useful to those involved in acoustic design and planning and it also gives insight into the way in which the performance of organ music is perceived by the organist and by listeners, as any measurements on the organ must recognise above all that its function is to make music.

333 

Sound and Flow at the Mouth of Flue Organ Pipes, Part II: Transient State

G. Paál [1], J. Angster [2], W. Garen [1] and & A. Miklós [2]
1. Fachhochschule Ostfriesland, Emden, Germany
2. Fraunhofer Institut für Bauphysik, Stuttgart, Germany

Apart from the harmonic content of the stationary tone, the subjective perception of the sound character of an organ pipe is determined by the initial development of the tone, the so- called attack transient. The evolution of the tone is intrinsically linked to the development of the jet and its ability to start vibrating. The knowledge of the transient flow with good temporal and spatial resolution is therefore necessary. The optical and acoustical techniques, described in the accompanying paper, have been applied here to the attack in real organ pipes. The transient development of the jet within the mouth is illustrated on a series of time ordered photographs. The temporal history of the axial and cross components of the flow velocity at various spatial positions are presented. Typical stages of the attack transient known from pressure measurements can be recognized. Under certain circumstances overtones within the velocity signal are visible. As far as acoustic is concerned, the transient development of the first nine overtones using a specialized "running window" FFT is shown. The influence of certain voicing steps is analysed.

339 

Spectral Properties of the Edge Tone of a Flue Organ Pipe Model

S. Pitsch [1], J. Angster [2], M. Strunz [1] and A. Miklós [2]
1. Institut für Aero- und Gasdynamik, Universität Stuttgart, Germany
2. Fraunhofer Institut für Bauphysik, Stuttgart, Germany

The spectra of the edge tones produced by a model of the mouth and the foot of a flue organ pipe (Diapason 8' C) have been studied in a series of experiments. The investigation was initiated by the interesting results of recent flat-water channel flow visualisations of the flow through of a 2-dimensional model representing an enlarged longitudinal section of the pipe foot. It has been found that two distinct flow paths exist, resulting in different jet parameters at the flue exit. The existence of both flow states has been supported by the acoustic measurements, which have been carried out in an anechoic room. The structure of the edge tone spectrum depends strongly on the flow path. The frequencies of the corresponding components are slightly shifted. The dependence of the spectra on the flue geometry and outflow velocity has also been investigated. The possible influence of the presented results on the sound generation of flue organ pipes is discussed.

345 

Effects of Material Choice and Tooling Methods on Structural Modes of Open Organ Pipes

Anna Runnemalm
Experimental Mechanics, Luleå University of Technology, Sweden

How are wall vibrations of organ pipes influenced by material choice and tooling methods ?

Six groups of three equally made diapason organ pipes (tuned to C4 at 260 Hz) fabricated out of two different alloys and with three tooling methods are investigated. All experiments are performed with the pipes mounted in an experimental organ. Results from the following experiments are compared:

The results show that structural vibrations are affected by the choice of material and tooling; a pipe with higher tin contents have higher eigenfrequencies. It is also shown that the voicing process selects certain modes of vibration in the pipes.

353 

Measurement of Newly Defined Energetic Indicators of the Steady Sound Field inside an Organ Pipe

Domenico Stanzial, Davide Bonsi and Nicola Prodi
CIARM c/o Department of Acoustics, CNR - Cemoter, Cassana, Ferrara, Italy

The measurement of three newly defined sound field energetic indicators introduced in a recent paper [1] has been carried out inside an organ pipe. The internal steady sound field has been monitored all along the axis of the pipe by means of a B&K 4181 intensity probe in the "side by side" configuration and the acoustic signals coming from the two microphones have been processed using the B&K 2133 intensity meter. In order to get the values of the three energetic indicators, a post-processing of the collected data for the time-averaged squared pressure, air particle velocity and active intensity has been performed running dedicated programs on a PC. The experimental data will be reported in the paper and a preliminary interpretation of the results will be presented.

1. D. Stanzial, N. Prodi, G. Schiffrer, Reactive intensity for general fields and energy polarization; J. Acoust. Soc. Am., 99(4): 1868-1876, April 1996.

359 

Vibration Behaviour of Organ Flue Pipes

Lothar Zipser and Heinz Franke
Hochschule für Technik und Wirtschaft Dresden, Germany

Oscillating fluid columns in tubes stimulate the tube bodies to vibrations. This is important not only for the design of music instruments as organs or trumpets, but also for the avoidance of noise and vibrations of pipe lines.

The paper concentrates on measurements of the vibration response of thin-walled tubes, particularly of organ flue pipe bodies, which are stimulated by oscillating air columns inside. Details concerning the interaction between the oscillating air column and the complicated motions of the tube body are presented.

Experiments show that the organ pipe body oscillates approximately like a thin-walled tube with one free end and one fixed end. A thin-walled tube vibrates radially as a quadrupole with axial modes superimposed at higher frequencies. However, both the shape and the vibration type of the labium, as well as the occasionally existing tuning notch at the open end of the organ pipe cause considerable deviations from the theoretical vibration patterns. Examples of typical vibration figures will be shown.

Furthermore, considering the results mentioned above, the problem of sound generation and radiation from organ pipes should be regarded in a modified sight. After all, the disputed problem of the influence of material and design of the pipe body on the sound quality of organ flue pipes becomes more transparent.

The investigations include modern and historical metallic and wooden organ flue pipes of several German masters, e.g. of the known Gottfried Silbermann.

The measurements are carried out by a modern laser scanning vibrometer, sound level meters and an equipment for rotating the tubes and pipes under investigation.

367 

Investigation of Jet Motion in Flutes

A. Bamberger and H. Wentsch
University of Freiburg, Germany

This investigation intends to measure jet properties in flutes. The classic flute covers more than three octaves by overblowing. Various recipies are described in textbooks in order to facilitate the overblowing, but they are inadequate in terms of the properties of the exctitation mechanism.

In contrast to flue pipe investigations of organs there are only a few investigations published, let alone examples of jet visualisation. The flow visualisation through "Schlieren"-methode was used to search higher modes starting with a flue pipe. A mock-up of the lips of the flute player was constructed and above methode applied to the flute. In spite of smaller size of the jet and the obstruction of the optical path by the embochoure of a normal flute some main properties of jet movement can be displayed. For more quantitative investigations - with the aim to be extended to spectral analysis - the hot wire anamometry (DANTEC, 1 micrometer wire diameter, temperature compensated) has been applied. First results of jet velocity profiles and scaling properties in flutes are presented.

373 

Prediction and Measurements of Exhaled CO2 Effects in the Pitch of Wind Instruments

Leonardo Fuks
Music Acoustics PhD Programme, Royal Institute of Technology, Stockholm, Sweden

The fundamental frequency in wind instrument playing depends on the properties of the gas inside the instrument. Also, this gas continuously changes its composition with respect to the content of CO2 and O2 because of the player's metabolism. These changes should affect the fundamental frequency to some extent. The purpose of the present study was to provide an experimental and theoretical basis for further analysis of this phenomenon by documenting the CO2 variation during performance of sustained tones and musical phrases in wind instrument blowing. A theoretical-numerical approach is applied to determine the dependence of sound velocity on the percentage of CO2 contained in the air. Realistic performance data were obtained from experiments in which a professional musician played a clarinet and an oboe, while the CO2 content of exhaled air was recorded together with the audio signal. By calculating the impact of the variation of CO2 and O2 contents on sound velocity, considerable effects on the fundamental frequency of the tones produced are predicted. As a way of corroborating the predicted effects an experiment is done in which instruments, an oboe and a clarinet, are artificialy blown with air at different gaseous proportions of CO2 and O2.

379 

Measurements of Sounding Frequency as a Function of Blowing Pressure in the Soprano Recorder

Mary Derengowski-Stein
Montclair State University, U. Montclair, New Jersey, U.S.A.

Results are reported from a series of experimental measurements on a soprano recorder. These include determination of the passive resonance frequencies for the instrument at bore configurations corresponding to fingerings for several different notes. In addition, measurements have been taken of the sounding frequency as a function of blowing pressure for several of these fingering configurations. The plots of sounding frequency versus blowing pressure exhibit plateaus in the vicinity of the resonance frequencies, as expected, with abrupt transitions from one plateau to the next as blowing pressure is changed. Hysteresis effects are observed for two of the bore configurations; that is, the transitions between plateaus occur at different pressures depending on whether the pressure is increasing or decreasing. The results are interpreted with reference to a transverse wave propagating on the air stream in the gap between the mouthpiece slit and the lip of the air column. The phase delay in the gap is calculated for each data point. Most of the resonance plateaus are found to correspond to a range of phase delays between approximately 100 and 180 degrees.

385 

Signal Analysis of Oboe Vibrato

Stephen Secan [1], Osamu Fujimura [2], and David M. Butler [1]
1. School of Music, The Ohio State University, U.S.A.
2. Department of Speech and Hearing Science, The Ohio State University, U.S.A.

The present study replicated elements of earlier studies on vibrato with the use of digital recording techniques and several computer analysis tools including crucially software (SNDAN) provided by J. Beauchamp. Anecdotal data were recorded in the form of interviews with widely respected oboists from leading American orchestras. Sound samples were collected from selected excerpts of recorded symphony performances. As a preliminary step, signals were expanded in time (2x) using cmusic. Time expansion was useful in particular for perceptual assessment of frequency fluctuation. Digitized samples were then analyzed with signal processing software including spectrographic displays to assess frequency and amplitude deviation. Both frequency and amplitude modulations, with specific patterns of correlation, were found to be critical factors with regard to timbre. Interaction of amplitude modulations of upper partials may be the acoustical basis for certain expressive effects, which are described as shimmer, rolling or spinning motions by the performers. Further study is necessary to relate perceptual effects to signal characteristics.


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Brass Instruments

391 

Brass Instruments: Theoretical and Experimental Results

Joël Gilbert [1] and Jean-François Petiot [2]
1. Institut d'Acoustique et de Mécanique, Le Mans, France
2. Laboratoire d'Automatique de Nantes, Nantes, France

This key-note paper on brass instruments is presented in three parts. We begin with a general presentation and illustrations of their bevaviour. We discuss the lips medelisation in the second part: lips between reed and vocal cords? Finally we discuss the effect of non-linear wave propagation in the instrument and the relation with the well-known "brassy sound": four hundred sonic bangs per second in a trombone! All of these parts are illustrated by experimental results obtained with an "artificial mouth".

Previous studies on reed musical instruments (clarinet, saxophone) have demonstrated the necessity of a mechanical device as a substitute for the musician. The latter exerts stable mouth control and makes it possible to take measurements during play (e.g. playing frequency) and to compare these with characteristic features of the instrument (e.g. resonance frequency).

In the same perspective we have developed an "artificial mouth" for brass instruments. With this mechanical system the trombone sound behaviour is very realistic (a video-film will be shown during the presentation). We have also made measurements in the permanent mode of play on steady self-excited oscillations.

Two kinds of results are presented. First, we have measured the harmonic distorsion in the input and output of the slide of the trombone. This allow us to underline the phenomenom of non-linearity of wave propagation, which determine the behaviour of brass instrument played at fortissimo level (bright "metallic" sound). Secondly, we present joint measurements of playing frequencies and resonance frequencies. These experimental results are compared with theory and numerical simulation.

The talk is illustrated by live trombone sounds and a video film.

401 

Variabilities in Trumpet Sounds

Matthias Bertsch
Institute für Wiener Klangstil (IWK), University for Music and Performing Art, Vienna

The development of theories and models concerning sound generation on brass instruments is in progress, but still quite uncertain because of its complexity. Properties plus qualities of the instrument and the characteristics of the musician produce a result that varies in many aspects. The paper starts with a description of sound influencing variables. Afterwards first results of a substantial audio-visual research study on trumpet playing are presented. One key question thereby is how the sound -played by many professional and student trumpet players using the same instrument- differs. Finally, a comparison of certain embouchures worked out by means of optical analysis is presented.

407 

The Influence of Valve Mechanism on the Microstructure of Slurs Played with Brass Wind Instruments

Gregor Widholm
Institute für Wiener Klangstil (IWK), University for Music and Performing Art, Vienna

The sound characteristic of brass wind instruments is highly determined by transients as there are the starting transients, slurs (transients between two "legato-notes") etc. Professionell brasswind player say, there is a distinct diffrerence in sound characteristic between instruments with rotary valves and instruments with perinet valves. New investigations show that not the type of valve but the position within the cylindrical tube determines the sound difference. Using new developed computer-systems, the situation for the lips of the player inside the mouthpiece during a slur can be illustrated by threedimensional plots. Consequences on playing technique and instrument design are discussed.

413 

Modeling Viscothermal Wave Propagation in Wind Instrument Air Columns

Maarten van Walstijn [1], John S. Cullen [2] and D. Murray Campbell [2]
1. Faculty of Music, University of Edinburgh, U.K.
2. Department of Physics and Astronomy, University of Edinburgh, U.K.

The theory of one-dimensional viscothermal wave propagation in cylindrical ducts is extended in this paper towards modelling acoustical tubes with non-uniform cross-section, with the purpose of developing efficient and accurate filter representations that can be applied in digital waveguide modelling of musical wind instruments.

Expressions for transmission-line parameters of a cylindrical duct model are adapted to obtain closed form expression for the `lossy' cone transmission coefficient. The use of such an expression is specifically desirable for truncated cones with a large difference between their end radii. Complete aircoloumns are approximated with piecewise conical sections for which the geometrical parameters are obtained through instrument bore measurements.

This waveguide model permits the inclusion of the effects of thermal gradients, a phenomenon that is very common for wind instruments under playing conditions.

A comparison is made between the waveguide model, a classical cylindrical section model, and input impedance measurements on a cornetto. Thermal gradients in the cornetto were produced using heating tapes.

The results of this paper provide improvements to the calculation of instrument resonance characteristics, as well as a new method of including viscothermal losses in digital waveguide models of wind instrument aircoloums.


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Modelling of Wind Instruments

419 

Physical Model of the Trombone including Nonlinear Propagation Effects

Régis Msallam, Samuel Dequidt, Stéphan Tassart, and René Caussé
IRCAM, Paris, France
A simple physical model for sound synthesis of the trombone including nonlinear propagation effects is presented. From theorical considerations, numerical simulations and measurements, we propose to take into account the nonlinear propagation effects only inside the slide of the trombone (i.e. the uniform section part), neglecting nonlinear interactions between the forward and backward waves but including linear damping (i.e. viscothermal losses). For sound synthesis applications, the characteristics method is used to propagate the waves from one end of the slide to the other. In this case waves are treated as simple plane waves (nonlinear travelling and frictionless waves). This method, which may also include variations of the length of the slide, is formulated as a time varying fractionnal delay digital filter. A special treatement based on the weak shock theory is given when shock waves occur. Viscothermal losses, propagation in the bell and radiation are treated in the simulation in a linear manner and the lips of the trombonist are described by a simple one-mass or two-mass model. Such a model can reproduce the typical brightness of the sound of the trombone at high levels of playing. Results will be presented and discussed.

425 

A Physical Model of Brass Instruments: Theoretical Results and Real-time Implementation

Christophe Vergez and Xavier Rodet
IRCAM, Paris, France

For several years, we have been developing and studying a physical model of brass instruments including the player's lips. By playing and improving this simulated instrument, we have obtained interesting theoretical results as well as remarquable sonic results . The model consists of either one or two masses, representing the lips, which are nonlinearly coupled to a linear sytem representing the bore. In developing our model we found some interesting features related to the basic behavior of brass instruments including the roles of the various forces acting upon the lips. Our model is a nonlinear dynamical system. An important aspect of this system is its behavior, particularly its oscillations, and the control of this behavior for musical applications. We show that the Hopf theorem can be applied to prove that the system possesses a unique stable periodic orbit when the fixed point becomes unstable. Furthermore, frequency and amplitude of the oscillating solution are predictable. We have also worked to improve the model in order to create a better approximation of natural instrumental sound production. Improved lip movements and dynamics are proposed. The coupling of the air flow and the lips has been more thoroughly studied. In order to provide musicians with an instrument which has true musical capabilities, we have developped a user interface and worked towards improving the ease of use, expressivity and flexibility which are essential from a musical point of view. A real-time implementation will also be presented and demonstrated.

433 

Scattering Parameters for the Keefe Clarinet Tonehole Model

Julius O. Smith and Gary P. Scavone
Center for Computer Research in Music and Acoustics (CCRMA), Music Department, Stanford University, Stanford, California, U.S.A.

The clarinet tonehole model developed by Keefe [JASA 88(1): 35-51] is parametrized as the cascade of a series reactance, a shunt complex impedance, and another series reactance. The transmission matrix description of this two-port tonehole model is given by the product of the transmission matrices for each of the three impedances. For implementation in a digital waveguide model, these "lumped" parameters of the Keefe tonehole model must be converted to traveling-wave scattering parameters. Such formulations have recently appeared in the literature [e.g., Valimaki, ICMC-93] based on a three-port digital waveguide junction loaded by an inertance as described in Fletcher and Rossing [Physics of Musical Instruments, Springer Verlag, 1990].

The scattering parameters of any high quality tonehole model are frequency dependent and therefore require a filter-design problem to be solved. Previously, Scavone and Smith [ASA-'96:5aMU8, Honolulu] addressed the scattering formulation of the Keefe tonehole model as implemented by a "four-filter", two-port scattering junction. This paper investigates an exact "one-filter" form for the Keefe tonehole scattering junction.

439 

Trombone Tone Synthesis Using Measured Lip Openings

David C. Copley and William J. Strong
Department of Physics and Astronomy, Brigham Young University, Provo, Utah, U.S.A.

Harmonic generation in trumpet tones can be largely accounted for by using a sinusoidally varying lip aperature as shown by Backus and Hundley. However, measured time-varying lip apertures exhibit significant harmonic components as shown by Copley and Strong. This paper is a report of trombone tone synthesis using measured time-varying lip apertures. The synthesis model consists of an air supply, the time-varying lip aperture, and the input and output impulse responses of the trombone. The mouth (blowing) pressure is calculated as the lung pressure minus the airway resistance times the flow. The flow is calculated from the pressure drop across the lip aperture and the time-varying lip aperture impedance. The tube (mouthpiece) pressure is calculated as the convolution of flow and tube input impulse response. The radiated pressure is calculated as the convolution of flow and tube transfer impulse response. Results of the simulation will be presented as plots of lip aperature area, flow, tube pressure, and radiated pressure. Recordings of the radiated pressure will also be presented.

445 

Physical Modelling based on the Analysis of Real Sounds

P. Guillemain, R. Kronland-Martinet and S. Ystad
CNRS-Laboratoire de Mécanique et d'Acoustique, Marseille, France

In this paper, we investigate sound analysis techniques in order to resynthesize instrumental sounds by the use of waveguide models. These models simulate the most important physical features of the sound generation, and are consequently well adapted to musical performance. We consider two different classes of musical instruments: transient excited ones, and continuously excited ones. In each case, we derive techniques for the estimation of the parameters of the model, based on an approximation of the spectral density of its impulse response. For one typical intrument in each class, namely the guitar and the flute, we compare the parameters estimated to the ones coming from the solutions of the movement equations. In the guitar case, the model takes into account the location of the excitation on the string as well as the resonance of the soundboard. In the flute case, it takes into account the interraction between the air jet and the acoustic pressure in a simplified way. Sound examples will be played, showing the relevancy of these techniques.


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Wind Instruments and Voice

451 

Real Time Acoustic Wave Separation in a Tube

Jean Guerard and Xavier Boutillon
Laboratoire d'Acoustique Musicale, Université PARIS VI, Paris, France
The separation of forward and backward acoustic waves in a tube can be performed in real time with two or more microphones. When the microphones are close together, an analog electronic device computes the spatial gradient of the waves, which is equivalent to the time derivative; then the waves are separated through time integration. This method is close to intensimetry, but we generalize the use of several microphones. Problems are signal-to-noise ratio and gain calibration error, bringing residues and diaphony.

The technique is first tested with pulse excitation into long tubes, in order to identify the separation. Then it is running in real time on short tubes. Applications like echo cancelling, acoustic reflectometry and impedance measurement are described and compared to existing methods.

A new kind of musical instrument synthesis is finally introduced; a flute mouthpiece is coupled at one end of a tube, while a real time controlled loudspeaker is fixed at the other end. When breathing in the mouth-piece (the excitator), this active tube behaves as a virtual device, longer or shorter than the real one, simulating the resonating part of the instrument. The musician plays the virtual flute as if it were a real instrument.

457 

Experiments with a Tone Hole of Continuously Adjustable Size and Position

Donald Hall and John Schreiner
Department of Physics, California State University, Sacramento, U.S.A.

When one wishes to obtain a note of a particular pitch from a wind instrument, this can be done with various combinations of tone hole size and position. In studying the acoustics of this tradeoff, it would be helpful to be able to change both the hole size and position at will while keeping the instrument the same in all other respects, yet without the complication of having several holes and having to cover the ones not in use. We will describe possible ways of doing this, including both discrete and continuous variation of hole size and position. We will demonstrate a model, built as a cylindrical extension for a recorder mouthpiece, that allows continuous variation. The adjustable tone hole makes possible relatively simple experiments for (1) comparing the effect of hole size and position upon fundamental frequency with approximate theories and (2) studying the effect of hole size and position upon departure from harmonicity of the first few natural modes of the instrument.

461 

Length Corrections for Woodwind Tone Holes

C.J. Nederveen
Pijnacker, The Netherlands
For accurately calculating the resonance frequencies of woodwinds, corrections (of hitherto insufficiently known magnitude) must be applied because the effective acoustic dimensions are not exactly equal to the geometric ones. The region in which the hole is localized is assumed to be small with respect to the wavelength so the corrections are distinguishable as local changes in compliance and inertance. Compliance changes are simply proportional to volume perturbations, but inertance changes are more difficult to determine. Depicting the 3D flow by an integration of 2D slices in parallel, accurate results were easily obtained, though with a systematic error. Exact results were obtained by numerically solving the Laplace equation using a 3D finite difference method. The method is free of systematic errors, but a large number of nodes (in our case up to 200 000) is necessary to obtain a satisfactory accuracy, which made computations lengthy. Shown will be results for the inertance correction at a closed hole, for the internal length correction to an open hole where it joins the bore and for open end corrections (a finite flange and a key hanging above the hole).

467 

Numerical Solution of the Horn Equation for Arbitrary Contours

Robert W. Pyle, Jr.
Cambridge, Massachusetts, U.S.A.

For many horn contours there are known solutions of the so-called "Webster" horn equation. However, for quantitative work on brass instruments, it is necessary to solve the equation for arbitrary contours, often specified in tabular numerical form. The present paper describes a numerical technique that is efficient and accurate. It can also include the effects of viscous and thermal damping at the walls of the horn. Like most numerical methods for solving differential equations, this breaks the range into a number of small pieces. However, here the pieces are not quasi-infinitesimal but can be large enough that the wave function can vary appreciably within each piece. The error is estimated and reduced in a series of consecutive approximations using a method called "the deferred approach to the limit". Double-precision calculations (approximately 15 signifiant figures) yield results accurate to about 6 or 7 decimal places for cases where the exact solution is known (e.g., lossless exponential horn). In regions of rapid flare, like the end of a typical brass-instrument bell, the horn equation itself fails to model real life this accurately.

473 

Wave Propagation in Acoustic Horns using Modal Decomposition

N. Amir
Center for Technological Education, Holon, Israel
V. Pagneux and J. Kergomard
Laboratoire d'Acoustique de l'Université de Maine, Le Mans, France

The input impedance of acoustic horns is often calculated in an approximate manner using solely the lowest order mode of an infinite uniform waveguide. Though all the higher order modes may be evanescent at the throat of the horn, the high degree of coupling between modes induced by the flare can have an important effect on the input impedance of the lowest order mode.

In this work we examine a method for finding the input impedance to a higher degree of accuracy, taking the higher order modes into account. The models discussed are a continuous model obtained by taking the discrete model to the limit, and a continuous model derived directly from the wave equations. We address here two main problems mentioned in the literature: the stiffness of the respective pressure equations, and the difficulties in fulfilling hard boundary conditions. Having overcome these problems we present solutions for a number of acoustic horns, comparing them to those using only the lowest order mode and to experimental results.

479 

On the Quantitative Relationship between Subglottal Pressure, Vocal Cord Tension, and Glottal Adduction in Singing

Bernd J. Kröger
Phonetics Institute, University of Cologne, Germany

The aim of this study is to establish rules for the control of an physiologically based glottis model for singing. The glottis model used is part of a pyhsiologically based model of the human sound production mechanism also comprising a pulmonary model and a vocal tract model. It is able to simulate the aerodynamics and acoustics of human sound production.

The quantitative relationship between acoustic-aerodynamic parameters (sound pressure level, fundamental frequency, glottal flow) and glottal control parameters (cord tension, glottal adduction, subglottal pressure) has been measured. Control strategies for singing were deduced from this relationship.

Using the condition of constant glottal flow our model is able to produce the range of pitches of the modal register. Increasing fundamental frequency is realized by increasing vocal cord tension, increasing subglottal pressure, and decreasing glottal adduction. The exact quantitative relationship between these three control parameters has been evaluated.

An acoustic demonstration of our synthetic singing voice will be given.


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Psychoacoustics

485 

The Automatic Recognition of Musical Instruments

Zaal Tsereteli
Tblisi, Republic of Georgia
To fulfil the "automatic recognition of the musical instrument" means to make a computer program for each given interval of the recorded music able to answer the question: "does the given note of the given musical instrument sound in this interval?". In order to do this, first, the precise values of spectral (i.e. timbral) components of given note and given interval must be determined and second, must be compared each to other. Two algorithms, realizing these two steps of the complete automatic recognition, are described. Codes of the sample programmes are enclosed.

491 

Number Theoretical Aspects of Harmony Based on Harmonics and Subharmonics

Alper Gonen
Department of Mathematics, Istanbul Technical University, Maslak, Istanbul, Turkey
Metin Arik
Department of Physics, Bogazici University, Bebek, Istanbul, Turkey

Any sound generated by a musical instrument contains overtones with harmonic frequencies thus associating frequencies which are in the ratio f:g = 1:n. g is called a harmonic of f and f is called a subharmonic of g. It is argued that as a first step sounds differing by ratios of two should be identified not by just name but also by defining an equivalence class. These ideas lead to a modified Euler consonance function and a nonstandard interpretation interpretation of the minor scale.

495 

Measuring the Timbre of the Human Voice: Analysing the Role of Voice Quality in Mother / Infant Communication

Stephen N. Malloch [1], David Sharp [2], A. Murray Campbell [2], D. Murray Campbell [2], Colwyn Trevarthen [1]
1. Department of Psychology, University of Edinburgh, U.K.
2. Department of Physics and Astronomy, University of Edinburgh, U.K.

Infants discriminate many parameters in maternal vocalisations and musical sounds: timing patterns, and shifts in pitch, loudness, and harmonic interval have all been tested, and have been shown to be co-ordinated with the facial and hand gestures of both mother and infant [1]. However, the changing timbre of mothers' vocalisations, which is widely acknowledged to be a major parameter in emotional expression, has been only superficially explored.

We have analysed plots of pitch, duration and timbre in mothers' speech and singing from recordings of natural, spontaneous and intimate interactions between infants (aged between 5 and 16 weeks) and their mothers. Pitch is plotted using a pattern recognition method [2]. In our analysis of timbre, roughness [3] and sharpness measures complement tristimulus plots [4] and graphs of timbral width [5]. These measures offer a variety of windows into the perception of vocal timbre. The results of these measures are compared with subjective voice quality assessment based on the procedure devised by John Laver [6]. This analysis of mother /infant communication supports the proposition that in her 'protoconversational' engagements with the infant, the mother responds with forms of expression that facilitate communication and assist development of the infant's innate sympathetic awareness of other persons' motives and emotions.

  1. Trehub, S. E.,Trainor, L. J. and Unyk, A. M. (1993) Music and speech processing in the first year of life. Advances in Child Development and Behaviour, 24: 1-35.
  2. Brown, J. C. & Puckette, M. S. (1993). A high resolution fundamental frequency determination based on phase changes of the Fourier transform. J. Acoust. Soc. Am. 94, 662-667.
  3. Hutchinson, W. & Knopoff, L. (1978) The acoustic component of Western consonance. Interface 7: 1.
  4. Pollard, H. & Janson, E. V. (1982) A tristimulus method for the specification of musical timbre. Acustica 51: 162 - 171.
  5. Malloch, S. & Campbell, A. M. (1995) The acoustic analysis of music performance with special reference to music timbre. Proc. 2nd International Conference on Acoustics and Musical Research - Ferrara, Italy: 421 - 426.
  6. Laver, J. (1980) The Phonetic Description of Voice Quality. Cambridge, Cambridge University Press.

501 

Further Studies of Pitch Perception in Children

E. Castro-Sierra [1], E. Paredes-Diaz [1], M. Gomez-Gama [2] and S.J. Perez-Ruiz [3]
1. Laboratory of Psychoacoustics & Department Of Neurosurgery, Hospital Infantil de Mexico, Mexico, D.F.
2. National School of Music, Mexico
3. Section of Acoustics of the Centre of Instruments, National Autonomous University of Mexico, Mexico, D.F.

The present research is a continuation of an investigation carried out at C.C.R.M.A., Stanford University (J.A.S.A. (1993) 93/4-2:2403), on the perception of the pitch of speech and music in children. We sought to determine whether male and female (N=120 (40x3)) 6 to 14 years of age, monolingual speakers of either Spanish, a tongue with prosodic pitch contrasts, or Otomi or Zapotec, Otomanguean tongues with lexical pitch contrasts between words, and having training in singing or in diverse musical instruments would perceive the pitch of speech as they perceived the pitch of musical sounds. Our data provide information that Spanish-speaking subjects at all ages and younger Otomi- and Zapotec-speaking subjects perceived the pitch of samples of their language in a manner that was similar to their perception of the pitch of synthesised musical samples. These results applied irrespective of musical background. On the other hand, older subjects speaking Otomanguean tongues seemed to perceive the lexical pitch shifts in words of their language in a manner contrasting with their perception of musical pitch. Neurosurgical studies are in progress to assess whether these differences are due to changes in the cerebral localisation of pitch perception in the course of central auditory development.


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History of Musical Acoustics

Joint session with the Colloquium on Historical Musical Instrument Acoustics and Technology, q.v.

509 

John Donaldson and 19th-century Acoustics Teaching in the University of Edinburgh

Christopher D.S. Field
Faculty of Music, University of Edinburgh, U.K.

Shortly after John Donaldson was appointed to the Reid Chair of Music in the University of Edinburgh in 1845, he began to purchase the scientific equipment and musical instruments he considered necessary for his lectures. His expenditure on acoustical apparatus and the construction of a new music classroom were not achieved without battles with the University authorities as Trustees of the Reid Bequest funds, culminating in a lengthy legal dispute which he won on appeal in 1855.

The great importance Donaldson placed on acoustics in the teaching of music was unusual in Britain at that time. Much of his acoustical apparatus was imported from the firm of Deleuil in Paris, but some was evidently made under his own direction. One such piece was a glass tube with tuning forks mounted at each end, constructed in 1856 for demonstrating standing waves by dust patterns. This demonstration is nowadays linked to the name of the German physicist Kundt, from his publication on the subject in 1866: however, Donaldson ten years prior to that was using such equipment.

Some of the equipment bought by Donaldson has survived, and will be exhibited at the time of the Colloquium.

521 

The History of Musical Acoustics: How the Scientific Understanding of Instruments has Evolved and How it has Influenced the Development of Instruments

Michael L. Djordjevic
Radio Belgrade, Serbia
Theme: Natural potential of tone pitches and their relations as primary base for development of acoustical musical thought and its application in technology of musical instruments building


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Historical and Traditional Wind Instruments

Joint session with the Colloquium on Historical Musical Instrument Acoustics and Technology, q.v.

527 

Non-conformistic Pipe Scaling for a Classical Organ

Dirk Steenbrugge
Gent, Belgium

An Italian Renaissance organ is being built using musical acoustics to assist the design. This organ type both has reached maturity in the XVth century, and has affinity with current research practice on organ pipes, through features such as a particularly homogeneous plenum sound, dominated by one basic pipe rank, uniform pipes -in some instruments all in wood- with low cut-up and open foot bore. General design considerations and pipe scaling are covered, the first steps in this project.

The musical idiom and measurements on extant instruments suggest how to semiquantify the desired sound throughout the ranks. Following current physical models, energy balances in the pipe as well as in the room are used to calculate approximate pipe scales. The windchest layout is computer-generated, based on, among others things, these pipe scales.

533 

Musical Acoustics of Dutch Wind Instruments from the Period of the Baroque

Rob Van Acht
Haags Gemeentemuseum and Institute of Sonology, Koninklijk Conservatorium, The Hague, The Netherlands
The physical construction and character of musical instruments from the baroque differ considerably from those in our time. Musical instruments are highly important as documents of the music of their period, as well as means of producing music, and are often also works of art in themselves. As they produce sound, the very few examples that are playable are very rich sources and subjects for the application of twentieth-century methods of acoustic analyses, such as spectrum analyses. Their sound and timbre can be examined and described, as can their their pitch (deviations) and the process of attack and decay. In many ways relatively new methods to describe, analyse and compare them in acoustical way are available now.

From March to April 1997 recordings and analyses were made of several wind instruments in the collection of the Haags Gemeentemuseum, The Hague, were made in collaboration with the Institute for Sonology at the Koninklijk Conservatorium in The Hague. Four recorders, eight oboes, five traversos, a clarinet and a bassoon were played and recorded from the following Dutch wind instrument makers: Richard Haka (1646-1705), Coenraad Rijkel (1664-1726), Thomas Boekhout (1666-1715), Abraham van Aardenberg (1672-1717), Jan Steenbergen (1676-c.1730), Engelbert Terton (1676-1752), Willem Beukers senior (1666-1750) or junior (1703-1781) Beukers, Albertus (1674-c. 1730) or Jan (1704-1750) van Heerde, Hendrik (1683-1727) and Frederik (1694-1770) Richters, Philip Borkens (1693-c. 1765), Robert (1698-1774) and Willem (18th c.) and Jan Barend Beuker (1737-1816). The results of the acoustical analyses will be presented and discussed.

541 

Using Pulse Reflectometry to Compare the Evolution of the Cornet and the Trumpet in the 19th and 20th Centuries

David B. Sharp [1], Arnold Myers [2] and D. Murray Campbell [1]
1. Department of Physics and Astronomy, University of Edinburgh, U.K.
2. Faculty of Music, University of Edinburgh, U.K.

Pulse reflectometry with improved accuracy has been used to study the acoustically-significant features of the bore profiles of brass instruments. The refinements in the technique which have permitted measurements sufficiently accurate to allow subtle discrimination between apparently similar instruments is outlined. The effects of leaks on the bore reconstruction techniques are discussed.

The commonly-held view that the cornet and the valved trumpet have evolved to become less easily distinguished is shown to be over-simplified, although broadly correct. It is also demonstrated that the modern trumpet has many resemblances to some models of early cornet.


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Historical and Traditional Stringed Instruments

Joint session with the Colloquium on Historical Musical Instrument Acoustics and Technology, q.v.

549 

Bowed String Parameters and the Hurdy Gurdy

Peter Dobbins
BAeSEMA, Bristol, U.K.

The behaviour of a bowed string depends upon various parameters that are generally under the direct control of the player. This control may be sub-conscious, but it allows the player a great deal of influence over tone quality.

The relevant factors include bowing speed, pressure and position, the angle between bow and string, and the amount of rosin on the bow. For the violinist this is a matter of skill and experience, but for a mechanically bowed instrument such as the hurdy-gurdy it becomes an engineering problem. The only variation allowed to the hurdy-gurdy player is bowing speed. Other parameters must be adjusted in setting-up, or are fixed by the maker.

This paper presents results from measurements that confirm that the hurdy-gurdy is a bowed string instrument in exactly the same way as a violin. This allows the use of established bowed string theory to set criteria that must be followed in construction if the instrument is to be successfully adjusted and played. It is also demonstrated that it is all too easy to produce an unplayable instrument.

However, within the range of acceptable adjustments, a lavish variety of sounds can be produced. The paper concludes by considering the artistic implications of these variations and the combinations of parameters that are most appropriate for playing music of different styles and from different periods.

555 

Acoustic and Dynamic Characterization of Different Hammers-sets in the Rossini Piano Pleyel "petit queue" Restoration

Alessandro Cocchi [1], Flavio Ponzi [2] and Lamberto Tronchin [1]
1. DIENCA, Faculty of Engineering, University of Bologna, Italy
2. Echo Historical Pianos, Bologna, Italy

This paper is intended as a contribution to defining the acoustic and dynamic characterization of (restored) hammers of pianos of the romantic period. Many authors developed different solutions in order to achieve a general characterization of the interaction between hammer and string, ranging from Hall to Askenfelt and Jansson. This research has been developed from a different point of view, being developed in a close conjunction between the restorer and the acoustician, taking into account the need of the "romantic performer" to play a restored instrument that could be able to give the sound efficiency as close as possible to the original one. The research has been carried out by replacing the original hammers in a piano petit queue (1844) played by Rossini during his Parisian exile (the treble hammers were not more usable, being the felt too worn) with two properly remade hammers-sets, characterized respectively by a lower density and a higher density of the felt (the both used in the Pleyel manufactory about 1840), and with a Pleyel hammers-set of 1846 recently restored in a "petit queue Pleyel". A compared Fourier analysis on all the notes of the keyboard between the two new hammers-sets, the hammers-set (Pleyel petit queue) of 1846 recently restored, and the bass hammers of the original hammers-set of the Rossini Pleyel, with different degrees of excitation, has been performed. A proper questionnaire has been developed, in order to point out the differences in timbre and dynamics with the different hammers. Subjective tests have been conducted, gathering many questionnaires among trained and a sharp-eared musicians after a performance of a "romantic pianist", showing an interesting difference in sound efficiency between the different hammers-sets.

561 

Acoustics of Historical Guitars

Bernard Richardson
Department of Physics and Astronomy, University of Wales, Cardiff, U.K.

Musical usage, technological change and mere whim have, over the centuries, resulted in significant changes in the materials and design of guitars and their ancestors. A study of the acoustics of historical instruments illuminates the important functional evolution of the instrument and helps to establish possible avenues for the instrument's future development. This study examines the musical usage, design, construction techniques and principal acoustical features of instruments of the "extended" guitar family from the sixteenth century to the present day.


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Historical and Traditional Percussion Instruments

Joint session with the Colloquium on Historical Musical Instrument Acoustics and Technology, q.v.

567 

An Acoustical Study for the Restoration of the Carillon in Perpinan - Characterization of Bell Dampings

Xavier Boutillon, Bertrand David and Benoit Fabre
Laboratoire d'acoustique Musicale, Université Paris 6, France

In order to acoustically qualify the restauration of the carillon of Perpignan, the modal parameters of each bell (including a precise determination of damping, which constitutes a novel feature) are measured at various stages of the restauration process. The analysis procedure is largely automated in such a way that it can be used eventually by bell-makers in their routine practice. The results show the inocuity of the sand-cleaning of the bells and also reveal an unexpected difference between the frequencies of hanged vs. laid bells.

573 

Acoustics of Ancient Chinese Bells

Thomas D. Rossing
Physics Department, Northern Illinois University, DeKalb, U.S.A.

Many ancient Chinese bronze bells, some more than 3000 years old, remain from the time of the Shang and Zhou dynasties. Most of these bells, being oval or almond-shaped, sound two distinctly different notes, depending upon where they are struck. Modal studies of original bells and of bronze copies reveal the modes of vibration ordinarily observed in round bells exist as mode doublets in these two-tone bells. After the 3rd century AD, round temple bells gradually replaced two-tone bells. The largest of these, cast in the 15th century during the reign of the Ming emperor Yongle, stands over 4.5 m high. Modes of vibration in some large temple bells will be discussed.

Further abstracts of papers on the history of Musical Acoustics are in the abstracts of the Colloquium on Historical Musical Instrument Acoustics and Technology organised jointly by the Edinburgh University Collection of Historic Musical Instruments and the Galpin Society, to be held in Edinburgh 22-23 August 1997.

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Further information from the Chairman of the Organising Committee:

Dr D.M. Campbell,
Department of Physics and Astronomy,
University of Edinburgh,
James Clerk Maxwell Building,
Mayfield Road,
EDINBURGH EH9 3JZ, Scotland

Tel +44 (0) 131 650 5262

Fax +44 (0) 131 650 5902

Web URL:- http://www.music.ed.ac.uk/research/conferences/isma/

E-mail communications to isma.97@ed.ac.uk

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This page updated: 25.08.97