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Article

Sigalia Dostrovsky, Murray Campbell, James F. Bell and C. Truesdell

This article is concerned with the history of vibration theory as it relates to music. For further information see Acoustics and Sound.

Sigalia Dostrovsky, revised by Murray Campbell

The basic ideas of the physics of music were first obtained in the 17th century. Acoustic science then consisted mainly in the study of musical sounds; in fact, music provided both questions and techniques for the study of vibration. Music gave experience in comparing the pitch and timbre of tones, and so the means for careful experiment on sound; musical instruments offered empirical information on the nature of vibration; and, rather remarkably, the Pythagorean ratios of traditional music theory provided frequency ratios.

Early in the 17th century it was realized that the sensation of pitch is appropriately quantified by vibrational frequency – that is, pitch ‘corresponds’ to frequency. This realization came as part of a preliminary understanding of consonance and dissonance. Once the correspondence had been made, it was possible to determine the relative vibrational frequencies of tones from the musical intervals they produced. When relative frequencies were known, there was the challenge of determining frequencies absolutely; and the first measurements were made during the century. The idea that pitch corresponds to frequency motivated efforts to understand overtones, since, during most of the 17th century, it seemed paradoxical that a single object could vibrate simultaneously at different frequencies. This paradox was resolved by the end of the century through an initial understanding of the ‘principle of superposition’. Also by this time the connection between overtones and timbre was noticed, and beats were explained quantitatively. During most of the century, sound was described as a succession of pulses, its wave nature being understood qualitatively. But late in the century the first mathematical analysis of the propagation of sound waves was made....

Article

R.W.B. Stephens

revised by Murray Campbell

(b Langford Grove, nr Maldon, Essex, Nov 12, 1842; d Witham, Essex, June 30, 1919). English scientist. He was educated at Cambridge University, where he was Cavendish Professor of Experimental Physics (1879–84); later (1887–1905) he held the professorship of natural philosophy at the Royal Institution, London, and in 1905 he became president of the Royal Society. He received jointly with Sir William Ramsay a Nobel Prize for the discovery of argon.

Rayleigh was perhaps the most versatile of British physical scientists from about 1850 to 1930 and, like Helmholtz, he covered almost all branches of physics and ventured into other disciplines. His monumental Theory of Sound (1877–8/R), written over five years, is often termed the ‘bible of acoustics’ and remains a standard treatise. Among Rayleigh’s contributions to acoustics was his extension of Helmholtz’s resonator theory. He also made more precise the corrections for open and closed resonating tubes, and gave a theoretical explanation of heat-maintained vibrations in pipes (the ‘Rijke sounding-tube’ effect). Additionally he carried out investigations on singing and acoustic sensitive flames and gave a more detailed explanation of ‘whispering galleries’, attributing the effect of the St Paul’s Cathedral gallery to the slight inward slant of the circular containing walls. He also investigated the binaural effect in sound and developed the phonic motor, of considerable value for frequency measurement. Rayleigh’s collected papers, which number over 400, were published in ...

Article

Arthur W.J.G. Ord-Hume, Jerome F. Weber, John Borwick and D.E.L. Shorter

This article is concerned with historical and technical aspects of the means for recording, reproducing and transmitting sound. The material covered in the first section includes, first, a history of recorded sound from mechanical to electrical means; secondly, a history of the various media and technologies used in recording; and lastly, a historical overview of the recording industry. The material covered in the second section includes, first, the conversion of sound into usable electrical energy by microphones; secondly, the employment of microphones and other apparatus in recording and broadcasting studios; thirdly, the recording of sound on disc, tape and film; fourthly, the transmission of sound by radio broadcasting; and lastly, the reproduction of sound through amplifiers and loudspeakers. For the history of music in radio and the influence of radio on musical life, see Radio.

Arthur W.J.G. Ord-Hume

The earliest attempts to obtain a permanent record of extempore performance were in the form of ‘notating devices’, normally attached to the action of a keyboard instrument. Apparently the first such machine was proposed in England by J. Creed, who wrote a ‘Demonstration of the Possibility of making a machine that shall write Extempore Voluntaries or other Pieces of Music as fast as any master shall be able to play them upon an Organ, Harpsichord, etc.’, published posthumously by the Royal Society in ...

Article

Murray Campbell

The lower-pitched tone that may be heard when a group of harmonically related pure tones is sounded quietly together. It can be distinguished from the difference tones because if all the components are raised in frequency by the same amount, the residue tone also rises, though not by the same amount. If a difference tone were present it would remain constant in frequency. ...

Article

Murray Campbell

A large amplitude of oscillation built up when a vibrating system is driven by an outside periodic force of frequency close to a natural frequency of the system. It plays an important part in the operation of almost all acoustic systems. In musical instruments, resonances are crucial in the generation or stabilisation of pitched sounds and are frequently employed to enhance sound radiation; on the other hand, a strong resonance can be a problem if a uniform response is required over a wide frequency range. ...

Article

Murray Campbell

The time taken for a loud sound to decay to an inaudible level (strictly, for the sound pressure level to decay by 60 dB). When a sound is created within a room, the initial waves are reflected back and forth between the walls and so the sound continues after the source has ceased to produce sound energy. If the walls are highly absorbent the persistence may be short and the room is then said to have a short reverberation time or a ‘dry’ acoustic quality. If the walls are highly reflecting (e.g. of glazed tiles and glass as in an indoor swimming pool) the reverberation may be long (up to four or five seconds) and the room is said to be ‘lively’ or ‘reverberant’. Good acoustic design demands (among other things) a balance between these extremes to suit the use for which the room is intended. The variation of reverberation time with frequency must also be considered. For example, if the wall covering is an efficient absorber at high frequency but reflects more sound at low frequency, the reverberation time will be longer for low than for high frequency giving the hall a ‘booming’ acoustic. ...

Article

Richard Orton

An electronic device used in both recorded and live electronic music. It is a standard item in electronic music studios, and can appear as a free-standing unit connected to other electronic apparatus, or as a module within a synthesizer. Existing in both analog and digital forms, the ring modulator takes its name from the characteristic ring formation of four diodes in its analog circuit (see illustration).

There are broadly two classes of instruments in an electronic music studio: sound generators and sound modifiers. The ring modulator is a sound modifier. It modifies the frequency components of a given sound (henceforward the ‘signal’), according to definite laws, in relation to those of a second source, or ‘carrier’. So a ring modulator has two inputs, the signal input and the carrier input, and one output. The modulator will function only if both inputs are present, and optimally when they are balanced, i.e. present at the same amplitude. The output consists of the sum and difference frequencies of those at the inputs. For example, if sine waves (i.e. pure tones) of frequencies 1000 Hz and 400 Hz are present at the inputs, the output will consist of the two frequencies 1400 Hz and 600 Hz. In practice, it matters little which input is regarded as the signal and which the carrier, since it is only the modulation products that matter. These products are called ‘sidebands'....

Article

Mark Lindley

(b Montpellier, Sept 14, 1723; d Montpellier, Nov 8, 1766). French dilettante and scientist. In December 1751 he announced his discovery of difference tones, which he had made by experiments with wind instruments. (Nearly three years later Tartini, evidently unaware of Romieu’s work, published his discovery of the same phenomenon observed in double stops on the violin.) Romieu’s ‘Mémoire théorique & practique sur les systèmes temperés de musique’, published in the 1758 Mémoires of the Académie Royale des Sciences, surveyed various regular tuning systems and expressed preference for ⅙-comma mean-tone temperament and its theoretical equivalent, the division of the octave into 55 equal parts.

E. Roche: ‘Notice sur les travaux de J.-B. Romieu’, Mémoires de l’Académie des sciences et lettres de Montpellier, 9 (1879)J.M. Barbour: Tuning and Temperament: a Historical Survey (East Lansing, MI, 1951/R, 2/1953)P. Barbieri: ‘Il “migliore” sistema musicale temperato: querelles fra Estève, Romieu e altri accademici francesi (c.1740–60)’, ...

Article

Murray Campbell and Clive Greated

(b Madison, SD, March 27, 1929). American physicist and acoustician. After studying at Luther College, Iowa (BA 1950), and Iowa State University (MS 1952, PhD 1954), he worked for the Sperry Rand Corporation. He was appointed professor of physics at St Olaf College, Minnesota, in 1957, then at Northern Illinois University in 1971. He has contributed greatly to the understanding of percussion instruments. Particularly noteworthy was his experimental demonstration of Chladni figures showing the vibrational modes of a kettledrum head (1982) and his work on bells (1984). His research with Johan Sundberg and colleagues in Stockholm revealed important features of the formant characteristics of the voice in solo and choral singing. He is best known as co-author of the influential The Physics of Musical Instruments (1991).

‘The Physics of Kettledrums’, Scientific American, no.247 (1982), 172–8 ed.: Acoustics of Bells (Stroudsburg, PA, 1984)...

Article

James F. Bell

revised by Murray Campbell

(b Richwood, OH, June 13, 1868; d Cambridge, MA, Jan 10, 1919). American acoustician. He studied at Ohio State University and Harvard, where he taught physics from 1890; between 1895 and 1919 he laid the foundations of architectural acoustics on the basic principles of engineering design. C.W. Eliot, president of Harvard, prevailed on Sabine to try to correct the serious problem of reverberation in the lecture hall of the Fogg Art Museum, his first acoustical project. At Eliot’s urging he also served as consultant for the Boston Music Hall: his outstanding success there illustrated the effects that could be achieved when acoustical engineering design preceded construction. Sabine’s discovery of the relation among reverberation time, absorbent capacity and the volume of an auditorium was a fundamental and new contribution; he earned a lasting reputation for the scope and perception of his work. It is indeed appropriate that the unit of sound-absorbing power is named the ‘sabine’. His ...

Article

C. Truesdell

revised by Murray Campbell

(b La Flèche, March 24, 1653; d Paris, July 9, 1716). French acoustician. In 1670 he went to Paris, where he attended the lectures of the Cartesian physicist Rohault; his works do not display the knowledge of advanced mathematics that characterizes the scientific progress of the age of Newton, although he held a chair of mathematics for a decade. He was elected to membership of the Académie des Sciences (1696), which left him free to develop his interest in acoustics. He thoroughly mastered the idea of frequency and was the first to interpret beats correctly. He also introduced the terms ‘acoustique’ (acoustics), ‘son harmonique’ (harmonic sound) and ‘noeud’ (node). His papers, though not so original as he may have thought them, were fairly clear and descriptive; they were very widely read, and certainly they had great effect upon the centrally important work of Daniel Bernoulli a quarter of a century later. He suffered from a speech defect and is said to have had no ear for music. His works include ...

Article

James F. Bell, R.W.B. Stephens and Murray Campbell

(b Mézières, June 30, 1791; d Paris, March 16, 1841). French scientist. He was trained at Strasbourg in medicine, taking a degree in 1816. He had long been interested in acoustics when, in 1816, he abandoned medicine and went to Paris, where he came under the guidance of Biot. He became a professor of natural philosophy in 1820 and was elected to the Académie in 1827, also obtaining an appointment at the Collège de France. He is known mainly for the Biot–Savart Law of Electrodynamics. His chief interest, indicated by the titles of his 27 papers (mostly published in the Annales de chimie et de physique), was in the study of vibrating bodies. These included important and often ingenious measurements of air, cords, bars, membranes, plates, solids of revolution and, particularly, vocal cords. He proposed theories of the vocal sounds of men and animals. His repetition and extension of Chladni’s experiments with sand figures on vibrating plates and longitudinal bars led in the early 19th century to controversy over the velocity of sound in solids. In ...

Article

Murray Campbell

(b 1892; d 1979). American engineer and acoustician. He had a distinguished professional career as an electrical engineer, specializing in research into radio wave transmission. In 1957 he retired from the directorship of radio research at Bell Telephone Laboratories. An enthusiastic amateur cellist, Schelleng undertook a programme of research into the acoustics of the violin family in his retirement. The combination of his musical experience and his background in electrical engineering resulted in a novel and extremely fruitful approach to the study of bowed string instruments, in which he drew an analogy between the exchange of vibrational energy between the string and the body of the instrument and the flow of electrical current round a circuit. His seminal paper, ‘The Violin as a Circuit’ (1963), provided the first realistic picture of how the violin functions as a whole, and became the foundation for most subsequent work in this area. Schelling was a pivotal figure in the group of researchers in violin acoustics which adopted the whimsical name Catgut Acoustical Society at his suggestion. He worked closely with Carleen Hutchins on the development of the Violin Octet, a set of new instruments based on the application of scaling theory to the violin. He was elected a fellow of the Acoustical Society of America in ...

Article

Murray Campbell and Clive Greated

A time-varying parameter which carries information. In the musical context, the signal is typically a fluctuating electrical voltage which, after appropriate amplification, can be applied to a loudspeaker to generate an audible sound. A musical signal may be generated in a variety of ways. A microphone senses the fluctuating pressure in a sound wave and converts it into an electrical signal. The pickup on an electric guitar generates a signal which depends on the string motion. In a synthesizer the signal is generated purely by electrical circuits. Once the signal has been generated, it can be modified by a range of techniques known collectively as signal processing. The most common of these are amplification, in which the signal is multiplied by a constant factor, and filtering, in which selected parts of the frequency spectrum of the signal are amplified or attenuated. The voltage output from a microphone is a continuously varying representation of the sound pressure. Neglecting any distortion introduced by the microphone, the voltage waveform is a strict analogue of the pressure waveform, and this type of signal is known as an analogue signal. Most modern signal processors and recording systems require that an analogue signal is first passed through an analogue-to-digital converter (ADC), which periodically samples the signal. The result is a sequence of numbers, representing the signal values at the sampling times, known as a digital signal....

Article

Murray Campbell

(b Gainsborough, 1689; d Cambridge, 1768). English mathematician. He entered Trinity College, Cambridge, in 1708, and became a senior Fellow in 1739 and Master in 1742; he was also a Fellow of the Royal Society and Plumian Professor of Astronomy (1716–60). His work on acoustics is contained in Harmonics, or the Philosophy of Musical Sounds (London, 1749/R, enlarged 2/1759) and Postscript … upon the Changeable Harpsichord (London, 1762). The first includes a table showing the rates of beating of tempered 5ths on the various notes of the scale calculated for a series of pitches of performance; the temperaments used are mean-tone and Smith’s own system of equal harmony. It is significant that his approach to the problem of tuning a keyboard instrument was through the judgment of the musician’s ear: he tried out his equal harmony on the harpsichord, and the first organ of the Foundling Hospital, with its system of alternative notes actuated by selective stops, is said to have been built under his direction. In several striking respects he anticipated Helmholtz, who, however, did not know his work....

Article

Sone  

Article

Sound  

Charles Taylor and Murray Campbell

This article gives an introduction to the scientific aspects of sound. For information on related topics see Acoustics (for matters connected with rooms, instruments and the human voice), Hearing and psychoacoustics, Psychology of music and Recorded sound; for the history of the study of sound, see Physics of music.

Greek and Roman sources include numerous references to scientific reflections on the nature and origin of sound, and these seem to be the earliest recorded thoughts indicating any attitude to music other than the purely aesthetic. Many classical observers, however, followed the Aristotelian method of thinking about an experiment and imagining the results, a method which, though of undoubted value as a starting-point, usually led to conflicting conclusions if not checked against real experiments. Also, a great deal of mysticism, especially concerning numerical relationships, tended to obscure more scientific ideas.

There followed a gap of 15–16 centuries during which there was no development in the scientific study of sound. But during the 16th and 17th centuries almost all of the great scientists of the time devoted at least some of their attention to the subject. Galileo made the first serious study of vibrating strings and gave a plausible explanation of the origin of consonance and dissonance, one that remains generally acceptable. He also introduced the idea of demonstration by analogue, including the use of pendula to demonstrate harmonic ratios. Boyle performed the classical experiment to show that a medium is needed for sound transmission; Descartes made studies of resonance; Hooke recognized that a sound of definite pitch can be derived from a rotating wheel; Mersenne formulated laws of vibrating strings (though Galileo had laid firm foundations in unpublished work); and Newton was the first to make a theoretical derivation of the velocity of sound and to compare it with experimental results....

Article

Edwin M. Ripin

(Fr. table d'harmonie; Ger. Resonanzboden; It. piano armonico, tavola armonica)

The thin sheet of wood in a piano, harpsichord, clavichord, zither, or the like, that serves to make the sound of the strings more readily audible and helps to form the characteristic tone quality of the instrument. A string presents so small a surface to the surrounding air that its vibrations cannot set the air into vibration with any great efficiency; as a result, the sound produced by a string in the absence of a soundboard, although it may well sustain for an appreciable time, is hardly loud enough to be used for any musical purpose. The soundboard, coupled to the strings by means of one or more bridges over which they pass, provides a larger vibrating surface so that the air can be set into vibration more efficiently and a louder sound can be heard. The soundboard does not serve as an amplifier in the same sense as an electronic circuit or device, since it adds no energy from an outside source; rather, it enables the energy already imparted to the string by a hammer, plectrum, tangent, or the like, to be dissipated more rapidly, so this energy is converted to a sound of higher intensity that lasts for a shorter time. The particular resonance and vibrational characteristics of the soundboard determine which components of the complex vibration of the string will be given particular prominence, and the rate at which they will be dissipated; consequently the shape, thickness and ribbing of the soundboard are of primary importance in determining the quality of the instrument of which it is a part....

Article

Murray Campbell

The initial sound produced when one vibrating system begins to drive another (e.g. string and soundboard, or reed and pipe). Although the time between the initiation and the emergence of a regular vibration may be very short, the starting transient produced in that time is one of the important characteristics distinguishing the sound of one type of musical instrument from that of another. ...