Research In Musical Acoustics Research Articles

Linearly-implicit schemes for collisions in musical acoustics based on energy quadratisation.

Collision modelling represents an active field of research in musical acoustics. Common examples of collisions include the hammer-string interaction in the piano, the interaction of strings with fretboards and fingers, the membrane-wire interaction in the snare drum, reed-beating effects in wind instruments, and others. At the modelling level, many current approaches make use of conservative potentials in the form of power-laws, and discretisations proposed for such models rely in all cases on iterative root-finding routines. Here, a method based on energy quadratisation of the nonlinear collision potential is proposed. It is shown that there exists a suitable discretisation of such a model that may be resolved in a single iteration, while guaranteeing stability via energy conservation. Applications to the case of lumped as well as fully distributed systems will be given, using both finite-difference and modal methods.

Silk purse? Brass-instrument research with limited resources

Can we make a silk purse from the proverbial sow's ear? That is, can we do meaningful experiments with inexpensive equipment? It is certainly much easier than it used to be. The advent of digital audio and cheap computing power has revolutionized musical acoustics research. In this paper the author looks at several projects on brass instruments, most of which he funded out of his own pocket. Some yielded better results than others, but all pointed toward interesting work yet to be done.Can we make a silk purse from the proverbial sow's ear? That is, can we do meaningful experiments with inexpensive equipment? It is certainly much easier than it used to be. The advent of digital audio and cheap computing power has revolutionized musical acoustics research. In this paper the author looks at several projects on brass instruments, most of which he funded out of his own pocket. Some yielded better results than others, but all pointed toward interesting work yet to be done.

The state of percussion research in musical acoustics: How we got here and where it is going

Drums are among the most ancient of all musical instruments and have been found in nearly all cultures across the world. This work covers a selection of major investigations of the acoustics of percussion instruments by a variety of scientists throughout history. Ernst Chladni’s efforts to characterize the vibration of plates are well known in acoustics and often replicated by students in the laboratory. Other scientists who made early contributions to the understanding of percussion instruments include Lord Rayleigh and C. V. Raman. Rayleigh’s observations of the acoustics of the kettledrum and bells represented only a fraction of his contributions to acoustics. Raman, who is remembered more for his work in spectroscopy, made detailed studies of the traditional Indian drum, the tabla. Modal analysis techniques used to investigate the acoustics of percussion instrument have evolved significantly in recent years. A brief review of current modal analysis techniques for studying percussion instruments is pre...

The Mechanical Invariance Factor in Musical Acoustics and Perception (Revisited)

Mechanical, acoustical, and neurophysiological investigations in music, acoustics, and auditory perception repose on the Pythagorean string ratio theory of musical pitch intervals (6^th century B.C). Recently, the mechanical validity of the string ratio theory and its psychological import have been challenged and denied on grounds of invariance. In this regard, Essien (2014) demonstrated experimentally that, contrary to established tradition in physics of sound, the tension of a string is not constant when string length is modified even though the balanced-force exerted on the string is held constant. The data revealed the existence of two sources of force in a vibrating string: (1) The oppositely-directed force applied externally to the string (labelled <i>F</i>ex); (2) The force that is the intrinsic property of the string (labelled <i>F</i>in). The latter is the missing parameter in Pythagorean auditory psychophysics. The omission lured researchers into acoustics and neurophysiology of pitch without an invariant physical correlate of pitch. Essien’s (2014) data showed that all transformations to string length or the balanced-force exerted on a string are various ways to modify the string’s resistance to deformation. Thus, the force in a string varies inversely with string length even though <i>F</i>ex is held constant. In the present paper, string length is shown to have very little or no effect at all on a string’s vibrational frequency and subjective pitch. Because psychoacoustic theories of hearing are founded on the string ratio theory, the data not only offer the missing psychological element that deprived the string ratio theory of a scientific status, but also refute both Ohm’s acoustical law (1843) and Helmholtz’s resonance theory (1877). The force in a string is portrayed as the mechanical parameter in control of pitch regardless of vibrational frequency or spectral structure. Implications for future research in musical acoustics and auditory perception are discussed.

Acoustics in a physics program in the 1990s

To a recent graduate from a liberal arts college with majors in physics and music, Dr. Bill Strong presented a unique opportunity to work on a graduate degree in physics, with research in musical acoustics, using a computational approach. The historical tradition of acoustics within the discipline of physics was important to that young graduate student then, in the 1990s, and continues to be important to this member of academia twenty years later. The work of Bill Strong in shaping and sustaining acoustics at Brigham Young University was at a critical juncture. This presentation of the contemporary setting and my mentor’s approach will offer a grad student’s perspective, through an appreciative filter of years of experience as a professor.

Stroboscopic illumination for electronic speckle pattern interferometry

A common realization of holographic interferometry is called Electronic Speckle Pattern Interferometry (or ESPI)—a technique capable of measuring harmonic modes of vibrating objects. We present a method of improving the contrast and quality of fringe patterns recorded with a simple, table-top ESPI system. In particular, by using stroboscopic illumination generated by an optical chopper, we are able to produce fringes that follow a cosine pattern, rather than the Bessel pattern fringes that result from time averaging. Since Bessel function amplitudes rapidly decrease for subsequent maxima, the stroboscopic cosine fringes show much better contrast. Also, because the zeros of cosine fringes are evenly spaced, it is much simpler to interpret the images to extract quantitative deformation amplitudes. We show that our results agree well with the theoretical predictions. This system was developed for use in musical acoustics research as a Senior Thesis project by an undergraduate student (Gavin). This low-cost, simple modification of the commonly used ESPI system could benefit other colleges and universities using holographic interferometry for acoustics research.

Adjusting the soundboard’s modal parameters without mechanical change: A modal active control approach

How do modes of soundboards affect the playability and the sound of string instruments? This talk will investigate this question experimentally, using modal active control. After identifying modal parameters of a structure, modal active control allows the adjustments of modal frequency and damping thanks to a feedback loop, without any mechanical changes. The potential of this approach for musical acoustics research will be presented for three different instruments: a simplified piano, a guitar, and a cello. The effects of modal active control of soundboards will be illustrated on attack, amplitude of sound partials, sound duration, playability, and “wolf tone” production.

A systems engineering approach to musical acoustics

Research in musical acoustics has benefited greatly from advances in technology; however, the ever increasing complexity of measurement systems may lend to inefficient experimental design and procedure. A systems engineering approach to experimentation can improve the process. Systems engineering involves the design of complex, many element, systems that maximize overall performance, considering all elements related in any way to the system, including human efficiency and the characteristics of each of the system's components. This paper explores how a background in the full product development lifecycle of a Raman spectroscopy based measurement instrument allowed for the rapid development of an automated directivity acquisition system (ADAS) used to measure a concert grand piano. Prior experience also assisted in adapting the ADAS to measure musicians when assessing elements like reliability, logistics, work-processes, and optimization methods. An account of how research in musical acoustics provides applicable experience for employment in a non-acoustics industry position will also be given.

High-Precision Regulation of a Pressure Controlled Artificial Mouth: The Case of Recorder-Like Musical Instruments

Dated: January 10, 2010 )Real-time regulation of air pressure in an arti cial mouth i s studied. A closed-loop strategyis developped, including a controller algorithm which upda tes (according to the dierencebetween the target and the measured blowing pressure) the el ectrical command sent to thesero-valve providing air ow. In this paper the targets cons idered may be steady states orslowly varying trajectories. Since both the musical instru ment and the servo-valve behavenonlinearly, the design of the controller algorithm requir es preliminary modelling and identi- cation steps in order to optimize the compromise performan ces/robustness. The controller nally adopted for the experiments is a PI (Proportional Int egral) whose integral gain isadapted according to an online estimator. Moreover, a caref ully tuned dither signal is addedon the electric command in order to limit consequences of fri ction inside the servo-valve.The high-precision regulation is used to investigate the fu nctionning of the recorder. Firstly,it allows to highlight the existence of aeolian sounds which had never been observed on arecorder. Moreover, the in uence of some small details of the chamfers geometry on theglobal behavior of the instrument is investigated. Hence th e in uence of the maker's workcan be evaluated, as well as the important consequences on th e possibilities oered to theplayer: with the optimized chamfers, the instrument can sou nd louder and the transitionbetween the two regimes is safer (larger hysteresis width).PACS numbers: 43.75.Ef, 43.75.Qr, 43.75.YyI. INTRODUCTIONBlowing machines (or arti cial mouths), were devel-oped since the early stage of research in musical acoustics(at least since 65 years,

Three decades of wind instrument research at Brigham Young Univ.

Wind instrument research at Brigham Young University during the 1970s, 1980s, and 1990s will be reviewed. In more or less chronological order, the research was as follows: (1) Calculation of input impedances of an oboe; (2) predictor coefficient analysis/synthesis of French horn tones; (3) functional model of a simplified clarinet; (4) calculated and measured modal frequencies of brass instruments; (5) calculation and measurement of flute impedances and standing waves; (6) calculation and measurement of horn impedances; (7) simulation of a player-clarinet system; (8) optimization of clarinet toneholes; (9) simulation of a player-trumpet system; (10) stroboscopic measurement of the lip motions of a trombone player; (11) calculation and measurement of nonlinear effects in loud trombone tones; (12) finite element modeling of the lips of a trombone player. [Work supported by the Institute for Research in Musical Acoustics.]

Robert W. Young’s eminence in musical acoustics

Interest in musical sound led Robert W. Young into physics graduate study at the University of Washington, where his 1934 doctoral thesis reported on standing waves within the Boehm flute. During subsequent research at C. G. Conn Ltd., Young and co-inventor Hugo Schuck developed the Conn Chromatic Stroboscope. It was the most precise frequency measuring instrument for acoustical research in the audio frequency range. Young’s book of tables for instrument users, From Frequency to Cents [1939; 2nd ed. (1952)], related frequency to cents deviation from the equally tempered musical scale. Research in musical acoustics, musical instruments, and pitch perception was especially benefited for decades, before computers became available. Young’s 63 research publications in musical acoustics concerned tuning of wind instruments, vibration of piano strings, temperature and humidity effects upon timing, inharmonicity of string vibration modes, and the resulting stretched scale of piano tuning. He was the associate editor for musical acoustics for the Journal of the Acoustical Society of America for 45 years, exerting a positive, and often creative, influence on research by authors around the world. He also served as associate editor for the acoustical patent review section of this Journal from 1943 to 1977, and personally reviewed thousands of patents, many on musical sound.

W. D. Ward as musical acoustician, journal editor, and reviewer

W. Dixon Ward’s musical talent as an expert pianist and a singer, combined with experience and training in both psychology and physics, provided the background for his significant doctoral research on pitch at Harvard University; for subsequent research in musical acoustics at the Baldwin Piano and Organ Company; and for continuing research in musical sound throughout his career. Twice Dix served the Journal as an associate editor for psychological acoustics. He peer-reviewed many Journal articles in psycho-acoustics, musical acoustics, and noise. He reviewed numerous books, and served on acoustical standards committees including acoustical terminology.

Physical Modeling Synthesis Update

Recent research in physical modeling of musical instruments for purposes of sound synthesis is reviewed. Recent references, results, and outstanding problems are highlighted for models of strings, winds, brasses, percussion, and acoustic spaces. Emphasis is placed on digital waveguide models and the musical acoustics research on which they are based.

Harvey Fletcher: Some personal recollections

The author of this paper describes his first visit with Harvey Fletcher in 1940 at the Acoustical Research Department of Bell Telephone Laboratories, then located on West Street in New York City. Five years later, he was invited by Dr. Fletcher to join the Laboratories. A brief description is given of some of the work carried out in Acoustical Research at that time. Upon his mandatory retirement at age 65, ‘‘Uncle Harvey’’ accepted the position of Visiting Professor in the Department of Electrical Engineering at Columbia University. In 1951 the author left Bell Labs for a teaching position in Europe; on his return to the U.S. a year and a half later, he again sought Dr. Fletcher’s counsel and it was suggested he take Fletcher’s place at Columbia University. This made it possible for Dr. Fletcher to return to Utah, where he devoted the rest of his distinguished career to research in musical acoustics at Brigham Young University.

Harvey Fletcher and musical acoustics

Although the bulk of his work was concerned with various aspects of speech and hearing in communication, Harvey Fletcher had a longtime interest in musical acoustics. This interest is evidenced in his papers on perceptual aspects of musical tones, which stressed the complex interdependences of the percepts of loudness, pitch, and timbre on the physical parameters of intensity, frequency, and spectrum. However, his active involvement in musical acoustics research came to fruition only after he was released from other research, administrative, and teaching responsibilities. In conjunction with others, he explored perceptual aspects of piano, organ, violin, and percussion tones. His approach was that of analysis of natural tones, followed by synthesis of these tones based on the analysis results. Real and synthetic tones were presented to listeners who were asked to judge the tones as being real or synthetic. When listeners were unable to distinguish between the two, the synthetic tones were considered to contain all of the essential ingredients of the real tones. Fletcher’s papers in which this work was described will be reviewed and samples of his real and synthetic tones will be presented.

Musical acoustics

Abstract There has been a considerable upsurge of interest in musical acoustics over the last 10 to 15 years and this article is an attempt to summarize the present position in this multidisciplinary field. It first looks at the essential physics involved, reduced to its simplest terms, goes on to consider the relationships between real musical instruments and the resonance tubes and sonometers of the old text-books on ‘sound’ and outlines the history of the subject up to the Second World War. The main section then discusses areas of current study and the relevant measurement techniques in relation to three of the main groups of musical instruments. The article concludes with a discussion of some aspects of the difficult, but all-important, subject of psycho-physics and a brief attempt to predict the future prospects for research in musical acoustics

Twenty-Five Years of Musical Acoustics

Two highlights of musical acoustics of the past twenty-five years are the advent of practical electrical musical instruments and research on deviations from the regular in music. Included in the latter are studies of the vibrato, transient modifications of tone quality, departures of intonation from rigid scales. The “steady-state” concepts of the past now need refurbishing in the light of “deviation” evidence. An analysis of papers directly related to music and published in the first twenty-five volumes of the Journal of the Acoustical Society of America reveals a steadily increasing interest in musical acoustics until World War II. In common with other subjects the publication rate dropped sharply during the war. Publication in acoustics as a whole increased rapidly after the war, but interest in musical acoustics (at least as evidenced by papers in the Journal) did not revive. Patents on musical devices, however, now constitute a significantly larger percentage of the annual output of the U.S. Patent Office than was the case in 1941. Technology is outstripping research in musical acoustics; interest in research must be revived immediately for the benefit of those who will listen to music in the next twenty-five years.

An Audiofrequency Harmonic Generator System

For proposed research in musical acoustics, a simple compact generator system is needed in which the relative phase and amplitude of each harmonic may be varied independently. In order that the fundamental frequency may be shifted freely, it is necessary to secure sinusoidal wave forms from the individual generators without recourse to electric circuit filtering. The principle of operation is similar to that employed by Firestone and also by Kurtz and Larsen. However, relative amplitude is controlled by mechanically varying the condenser gaps, while the polarizing potential remains constant. Relative phase is controlled by angular displacement of the harmonic stators relative to the fundamental stator. The theory has been developed for the rotor and stator tooth forms which will give a sinusoidal rate of change of capacity between the two elements. The theory indicates that this stator form discourages the production of even ordered harmonics of the rotor tooth form. Results of harmonic analysis of the individual generators show that the production of undesired harmonics is very low. Any remaining harmonic impurity may be eliminated by means of a cancellation principle.