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Journal of the Acoustical Society of America

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Jul 1947

Volume 19, Issue 4, pp. 527-737

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An Institute of Musical Science—A Suggestion

Harvey Fletcher

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 527-531 (1947); (5 pages)

Online Publication Date: 17 Jun 2005

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This paper suggests the establishment of an Institute of Musical Science designed to provide a scientific basis and techniques whereby music may contribute more fully to the esthetic life of a larger number of people. The program of research of the Institute extends from the physics of the production of musical sounds to the psychology of their appreciation by listeners. It would measure and study audience reaction under a wide variety of conditions. It would undertake the experimental development of new musical instruments, of new electro-acoustical systems for the production or reproduction of esthetic sounds; and it would study the possibilities of synthetic orchestras and new techniques or orchestration. It would experiment in the application of sound effects to dramatic and operatic performances. Techniques would be worked out for the measurement of musical talent, and scientific apparatus developed for the musical education of individuals and the training of choral or instrumental groups. It would apply to the problems of music the techniques and instrumentalities which have been developed in the fields of acoustics, electrical communications, and electronics. Particular attention would be given to music in the home, and to applications to its needs of devices inherent in recent engineering advances.

The Place of Acoustics in the Future of Music

Harold Burris‐Meyer

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 532-534 (1947); (3 pages)

Online Publication Date: 17 Jun 2005

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Decay Rates of Piano Tones

Daniel W. Martin

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 535-541 (1947); (7 pages) | Cited 4 times

Online Publication Date: 17 Jun 2005

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Decay curves were recorded for an upright piano, a baby grand, and an electronic spinet. For some tones the partials were recorded separately. Decay rates for the electronic piano were measured at different levels of piano amplification. Analysis of the data reveals the degree of control exerted by the sounding board upon decay rate, particularly in the initial stage of decay. The significance of this control by the sounding board is discussed, in relation to the problem of electrical amplification of piano tones.

Musical Tone Qualities as a Factor in Expressiveness

Abe Pepinsky

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 542-544 (1947); (3 pages)

Online Publication Date: 17 Jun 2005

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Music as an Aid to Healing

R. C. Lewis, Harold Burris‐Meyer, and R. L. Cardinell

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 544-546 (1947); (3 pages)

Online Publication Date: 17 Jun 2005

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Music in Industry Today

R. L. Cardinell and Harold Burris‐Meyer

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 547-549 (1947); (3 pages)

Online Publication Date: 17 Jun 2005

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Frequency Range Preference for Speech and Music

Harry F. Olson

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 549-555 (1947); (7 pages)

Online Publication Date: 17 Jun 2005

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Frequency range preference tests for reproduced speech and music indicate that listeners prefer a restricted frequency range in monaural reproduced speech and music. In order to obtain a better understanding of the reason for the preference of a restricted frequency range in reproduced sound, a fundamental all‐acoustic frequency range preference test has been made. An acoustical filter was placed between the orchestra and the listeners and arranged so that the filter can be turned in and out. A sheer cloth curtain which transmits sound without any appreciable attenuation was placed between the acoustical filter and the listeners. The curtain was illuminated so that the listeners could not see what transpired behind the curtain. The response‐frequency characteristic of the acoustical filter was 5000‐cycle low pass transmission. The response approximated a good commercial radio or phonograph. The tests made up to the present time have been conducted in a small room which simulates the average living room in dimensions and acoustics. A six‐piece orchestra playing popular and semi‐classical music was used in these tests. Tests involving one thousand listeners indicated a preponderant preference for the full frequency range. Similar results have been obtained for speech.

Acoustical Properties of Homogeneous, Isotropic Rigid Tiles and Flexible Blankets

Leo L. Beranek

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 556-568 (1947); (13 pages) | Cited 9 times

Online Publication Date: 17 Jun 2005

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Studies on rigid acoustical tiles and soft blankets are described in this paper. It is shown that two waves travel through the material—one primarily airborne and the other primarily structure‐borne. From a knowledge of the density of the sample, the volume coefficients of elasticity of the air and of the skeleton of the material, the porosity, the air flow resistance, the inter‐fiber frictional resistance, and the structure factor, the propagation constants of each of these waves can be calculated. The experimental results indicate that the theory is useful in calculating the performance of the flexible, airplane type of blankets over the entire audible frequency range. For rigid tiles, however, the theory appears to fail at frequencies above 1000 c.p.s. if the flow resistance is high, and it fails at all frequencies for materials with low flow resistance. Experiment shows that the condensations and rarefactions of the gas in blankets take place isothermally at low frequencies and adiabatically at high. The transfer from one state to the other occurs gradually in the 100 to 2000 c.p.s. region. A more complete theory is required to explain the effects of thermodynamic and viscous losses on the propagation constant of rigid materials.

Acoustical Impedance of Enclosures

Fred B. Daniels

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 569-571 (1947); (3 pages) | Cited 5 times

Online Publication Date: 17 Jun 2005

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Formulas are derived for the acoustical impedance of three types of enclosures, a sphere, a cylinder, and a narrow rectangular box. The solutions are valid throughout the entire range from adiabatic to isothermal conditions.

The Diffraction of Sound Due to Right‐Angled Joints in Rectangular Tubes

John W. Miles

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 572-579 (1947); (8 pages) | Cited 4 times

Online Publication Date: 17 Jun 2005

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The diffraction of a plane wave of sound caused by right‐angled joints in rectangular tubes is computed by calculating the impedance elements of the equivalent circuit for the discontinuities, the propagation of the principal wave being represented by the voltage and current on a transmission line. A numerical example is given.

The Equivalent Circuit for a Bifurcated Cylindrical Tube

John W. Miles

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 579-584 (1947); (6 pages)

Online Publication Date: 17 Jun 2005

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Using the impedance concepts developed in earlier papers, the problem of the diffraction of sound, caused by a bifurcation of a cylindrical tube, is solved. The equivalent circuit elements are shown to be related to the analogous changes of cross section. It is shown that the transmitted power is divided between the two tubes resulting from the bifurcation in proportion to their areas and without frequency distortion or reflection, and that the bifurcation may, therefore, be regarded as taking place in a virtual plane parallel to, but somewhat removed frown, the geometrical plane. A formula is given to locate this plane.
The results are applied to a concentric‐circular bifurcation and to a rectangular‐tube bifurcated parallel to one of its walls. Numerical results are given which may be applied both to the circular change of cross section and to the concentric bifurcation of a circular tube.

The Growth of Auditory Sensation

W. A. Munson

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 584-591 (1947); (8 pages) | Cited 8 times

Online Publication Date: 17 Jun 2005

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The integration of sensation with respect to time was studied experimentally by means of tones of short duration. Loudness tests were made on sounds persisting from 0.005 to 0.2 second and covering a wide range of levels. The observed increase in magnitude of a sensation as the duration time is increased is attributed to the integration characteristic of the central nervous system, and an equivalent electrical circuit is derived. The circuit analogy is then used in the computation of loudness as a function of the duration of the stimulus.

A Pulse‐Tone Technique for Clinical Audiometric Threshold Measurements

Mark B. Gardner

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 592-599 (1947); (8 pages)

Online Publication Date: 17 Jun 2005

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The pulse‐tone method of testing hearing, used as a basis for the 1939–40 World's Fair tests in which over one million individuals voluntarily participated, has been adapted for clinical audiometric use. For this purpose, a tri‐functional control has been utilized consisting of (1) an electronic method of producing the desired number of tone pulses (normally one, two, three, or four) in a selected sequence under control of the operator, (2) a visual signal which occurs at the beginning of each pulse series to act as a warning to the observer, and (3), a visual signal which flashes in synchronism with the output tone pulses to act as a counter for the operator. In threshold tests in which both the pulse‐tone method and the standard audiometric method were used, approximately three out of every four operators and a similar percentage of observers expressed a preference for the pulse‐tone procedure. For the very young listener, the pulse‐tone test appears to be preferable in the majority of cases. The normal threshold intensity calibrations of the two tests are in good agreement so that either test may be used interchangeably with the other. The time required to make a pulse‐tone audiogram is slightly in excess of that required to make a measurement by the standard procedure, but the resulting data are more reproducible.

Auditory Thresholds of Short Tones as a Function of Repetition Rates

W. R. Garner

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 600-608 (1947); (9 pages)

Online Publication Date: 17 Jun 2005

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Auditory thresholds were obtained for repeated short tones (sine‐wave) with repetition rates between ¼ and 100 per second, and tone durations between 1 and 50 milliseconds. Both noise‐masked and quiet thresholds were measured, Although the total energy in a stimulus can be changed by varying either the repetition rate or the duration, the results show that only in the latter case is there an equivalent shift in the threshold. Discussion of the results in terms of spectral distribution of energy of such tones leads to the conclusion that the ear does not perform a Fourier analysis of these tones. Further discussion indicates the conditions necessary for temporal integration of acoustic energy by the ear.

Sensitivity to Changes in the Intensity of White Noise and Its Relation to Masking and Loudness

George A. Miller

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 609-619 (1947); (11 pages) | Cited 12 times

Online Publication Date: 17 Jun 2005

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Sensitivity to changes in the intensity of a random noise was determined over a wide range of intensities. The just detectable increment in the intensity of the noise is of the same order of magnitude as the just detectable increment in the intensity of pure tones. For intensities more than 30 db above the threshold of hearing for noise the size in decibels of the increment which can be heard 50 percent of the time is approximately constant (0.41 db). When the results of the experiment are regarded as measures of the masking of a noise by the noise itself, it can be shown that functions which describe intensity discrimination also describe the masking by white noise of pure tones and of speech. It is argued, therefore, that the determination of differential sensitivity to intensity is a special case of the more general masking experiment. The loudness of the noise was also determined, and just noticeable differences are shown to be unequal in subjective magnitude. A just noticeable difference at a low intensity produces a much smaller change in the apparent loudness than does a just noticeable difference at a high intensity.

Physiological Noise Generated under Earphone Cushions

W. J. Brogden and George A. Miller

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 620-623 (1947); (4 pages)

Online Publication Date: 17 Jun 2005

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Listeners were required to match the quality and intensity of a low frequency ambient noise to the quality and intensity of the noise which they heard when they held earphones over both ears. A sound‐pressure of 55 or 60 db of rumbling, low frequency noise can be generated by the tremor of the tonic contractions of hand and arm muscles.

A Theory as to the Function of the Scala Tympani in Hearing

Louis A. de Rosa

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 623-628 (1947); (6 pages)

Online Publication Date: 17 Jun 2005

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The scala tympani canal is assumed to be coupled to the scab vestibuli of the cochlea through‐out its length. If the mathematics are formulated for this premise, with appropriate boundary conditions, it is found that despite the absence of reflections and standing wave patterns, there is, nevertheless, an area of maximum stimulation of the basilar membrane as a function of frequency. Interpretation of various acoustical phenomena is simplified by reference to this analysis.

Binaural Versus Monaural Hearing

John W. Keys

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 629-631 (1947); (3 pages)

Online Publication Date: 17 Jun 2005

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Construction and Calibration of an Improved Bone‐Conduction Receiver for Audiometry

R. W. Carlisle, H. A. Pearson, and P. R. Werner

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 632-638 (1947); (7 pages) | Cited 1 time

Online Publication Date: 17 Jun 2005

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The construction of an acoustically shielded bone‐conduction unit is described. The masses and springs have been proportioned for optimum purity of wave form at low frequency and for extension of the high frequency range to over 12,000 cycles.
The precautions taken in preparing an acoustical loudness‐balance calibration are described, and the reproducibility of observations is considered. Methods of specifying the response of productions units are shown.

Broadened Criteria of Hearing Aid Performance

August B. Mundel and Richard W. Carlisle

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 639-644 (1947); (6 pages)

Online Publication Date: 17 Jun 2005

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The requirements of hearing aid users include, besides adequate acoustic response, low reaction to “noise” excitation and other characteristics.
Methods used in reducing unwanted sensitivity are discussed. Other operational features of a hearing aid are considered, and a single chart method of presenting acoustic input‐output characteristics, frequency response, and distortion is described.

Reaction of Small Enclosures on the Human Voice

Charles T. Morrow

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 645-652 (1947); (8 pages)

Online Publication Date: 17 Jun 2005

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The paper concerns itself primarily with the acoustical specifications necessary for intelligible speech transmission through radiating enclosures, such as gas masks, placed on the front of the head. The results apply to enclosures whose internal dimensions are small by comparison with the wave‐lengths significant for speech. Transmission through larger enclosures is in general poor. A speech transmitting device for a gas mask will ordinarily consist of a diaphragm, a perforated protective cover, and an exhaust valve. The acoustical system, however, must include the cavity between the mask and the face. The enclosures considered here radiate through a circular constriction, a set of perforations, or a diaphragm; specifications for the more complicated case of a diaphragm and cover have not been obtained, but may be inferred from the data presented here. The enclosures all behave as Helmholtz resonators when tested on an artificial voice. They may be specified acoustically by the resonant frequency, and a quantity related to the inertance of the acoustical system. It has been found convenient to express this property of a set of perforations or of a diaphragm in terms of an effective diameter: the diameter of the circular constriction that results in the same resonant frequency for the enclosure, or, in other words, has the same inertance. The intelligibility obtainable through an enclosure increases when either the resonant frequency or the effective diameter is increased. In general, the intelligibility will be satisfactory if the resonant frequency is at least as high as 1500 cycles per second, provided that the effective diameter is at least 1.25 inches.

Effects of Impulsive Interference upon A‐M Voice Communication

J. C. R. Licklider and S. J. Goffard

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 653-663 (1947); (11 pages) | Cited 1 time

Online Publication Date: 17 Jun 2005

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The degree to which noise impairs the intelligibility of speech depends upon the characteristics of the noise. In this paper, which is concerned with electrical interference and radio communication, the questions are: (1) “what characteristics of the noise determine the degree of impairment,” and (2) “what are the functional relations between intelligibility and the important characteristics of the noise?” Answers to these questions were obtained with the aid of articulation tests, conducted with a typical amplitude‐modulation system and with a variety of electrical interferences.

Properties of Liquids at High Sound Pressure

H. B. Briggs, J. B. Johnson, and W. P. Mason

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 664-677 (1947); (14 pages) | Cited 3 times

Online Publication Date: 17 Jun 2005

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When sound of high amplitude is transmitted into a liquid by means of a mechanical driving device, the ultimate limitation to the power that can be transferred is cavitation or breakdown of the liquid under high internal stresses. A study of cavitation has resulted in establishing the following results. Under steady‐state conditions, light liquids filled with air cavitate when the negative acoustic pressure reaches the atmospheric pressure. When liquids are degassed, their natural cohesive pressure becomes effective and they will withstand a negative acoustic pressure. It is found that the total negative pressure required to cause cavitation is equal to the sum of the cohesive pressure—tensile strength—and the ambient pressure. Viscous liquids have a higher cohesive pressure and a proportionality has been established between the logarithm of the viscosity and the cohesive pressure. The amount of power that a liquid can withstand increases markedly as the pulse length is shortened.
An explanation of these phenomena is attempted on the basis of Eyring's theory of viscosity, plasticity and diffusion. On this theory natural holes exist in the liquid into which molecules can jump, leaving holes behind them. A jump occurs when the molecule has accumulated enough heat energy to surmount an activation potential barrier of energy value E0. Cavitation appears to be the result of coalescing of the natural holes in the negative pressure phase of the cycle. Since a molecule has to jump from a hole in order that this can coalesce with another hole, the cavitation pressure is proportional to the activation energy which in turn is proportional to the logarithm of the viscosity. The increased power‐transmitting capacity for short pulse lengths is a result of the finite time taken for the small holes to grow in size to a large enough hole to cause rupture of the liquid.

The German Use of Sonic Listening

Lee E. Holt

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 678-681 (1947); (4 pages)

Online Publication Date: 17 Jun 2005

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The most successful German sonic listening device, the GHG Gruppen Horch Gerät, is described in general terms. Reference is made to the types of ships using the equipment and to the arrangement and placement of the hydrophone arrays. A brief account is given of the steps taken by the Germans to improve the operation of the GHG by streamlining the array and by altering its position on the hull. The simple but efficient electrical training device is explained, and bearing accuracy and range data, as reported by the Germans, are presented. The paper is based on technical reports received from Germany and on subsequent investigations. The most important of the sources consulted is the Navy Technical Mission Report prepared by Mr. Laurence Batchelder.

On the Radiation Problem at High Frequencies

M. Lax and H. Feshbach

J. Acoust. Soc. Am. Volume 19, Issue 4, pp. 682-690 (1947); (9 pages)

Online Publication Date: 17 Jun 2005

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The angular distribution of radiation from a vibrating cylinder of arbitrary cross section is considered in the limit of high frequencies. An inhomogeneous integral equation of the first kind is derived for the distribution and is solved by the method of steepest descents. The first approximation yields the “geometric optics” result in which every element of the radiator radiates normally to itself. Higher order terms are obtained for the case in which the boundary conditions on the radiator surface vary smoothly. The case of an abrupt change in boundary condition is also solved and exhibits typical diffraction effects. The techniques used in this paper have a wide range of applicability to problems of radiation and scattering of waves as they occur in field physics.
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