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Journal of the Acoustical Society of America

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Jan 1942

Volume 13, Issue 3, pp. 207-336

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The Acoustical Society and Noise Abatement

Paul E. Sabine

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 207-209 (1942); (3 pages) | Cited 1 time

Online Publication Date: 16 Jun 2005

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Report of Activities of the National Noise Abatement Council

George P. Little and F. Edgar McGee

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 211-213 (1942); (3 pages)

Online Publication Date: 16 Jun 2005

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City Noise

Shirley W. Wynne

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 214-216 (1942); (3 pages)

Online Publication Date: 16 Jun 2005

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What Can the Hospital Do About Noise?

Charles F. Neergaard

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 217-219 (1942); (3 pages)

Online Publication Date: 16 Jun 2005

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Industrial Noises and Industrial Deafness

Walter A. Rosenblith

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 220-225 (1942); (6 pages)

Online Publication Date: 16 Jun 2005

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Measurements on the intensity and the frequency distribution of industrial noises and the hearing losses of industrial workers show: (a) some degree of correlation between the average noise level and the temporary and permanent hearing losses; (b) an almost complete localization of the permanent hearing loss in the region above 1500 cycles (with a maximum at 6000 cycles), while the most important components of industrial noises are practically always below this frequency‐limit; (c) some correlation between the amount of temporary and permanent hearing losses for high frequencies; (d) a very small permanent hearing loss for low frequencies with a very rapid recuperation from temporary loss in this region.

The Velocity of Sound in Air

H. C. Hardy, D. Telfair, and W. H. Pielemeier

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 226-233 (1942); (8 pages) | Cited 4 times

Online Publication Date: 16 Jun 2005

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A rigorous equation is set up for the velocity of sound in gases. This is used to calculate the velocity of sound in dry air at standard conditions from data taken in independent measurements. The result of this calculation is 331.45±0.05 meters sec.−1 An extensive survey of previous reported measurements has been made. After proper corrections are taken into account, the weighted mean is 331.464±0.05 meters sec.−1 The results of very precise interferometer measurements by the authors give 331.44±0.05 meters sec.−1.

Polycylindrical Diffusers in Room Acoustic Design

John E. Volkmann

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 234-243 (1942); (10 pages)

Online Publication Date: 16 Jun 2005

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Performance of Broadcast Studios Designed with Convex Surfaces of Plywood

C. P. Boner

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 244-247 (1942); (4 pages)

Online Publication Date: 16 Jun 2005

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Acoustic Impedance of Porous Materials

Leo L. Beranek

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 248-260 (1942); (13 pages) | Cited 16 times

Online Publication Date: 16 Jun 2005

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A thorough understanding of the acoustical properties of porous materials is becoming increasingly important because of the wide variety of unusual and important applications in which they are finding use. A simple and useful theory is presented for predicting the normal acoustic impedance of isotropic porous materials in terms of three previously described simple constants, namely, flow resistance, porosity, and effective dynamic mass of the enclosed gas. The variation of normal impedance with angle of incidence for spaced‐out or rigidly backed samples is treated. A striking possibility is discussed, namely, that gaseous expansions are isothermal over most of the audiofrequency range in materials made of finely divided particles. Many isotropic acoustical materials appear to fall in this class. This means that an air cavity becomes less stiff to dynamic compression when a very porous finely divided material is added to the cavity than when the material is not present. The results are checked against experimental data. A simple method is described for measuring the porosity P of a material, namely, the ratio of the volume of the air spaces in a material to the total volume of the material.

An Acoustic Tube for Measuring the Sound Absorption Coefficients of Small Samples

D. P. Loye and R. L. Morgan

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 261-264 (1942); (4 pages)

Online Publication Date: 16 Jun 2005

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Properties of the Dulled Lacquer Cutting Stylus

C. J. LeBel

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 265-273 (1942); (9 pages)

Online Publication Date: 16 Jun 2005

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The recent improvement in disk recording standards is emphasized. The combined cutting and burnishing action of a standard lacquer cutting stylus is explained. It is emphasized that cutting and burnishing take place simultaneously (in terms of wavelength) at low frequencies; but that at higher frequencies the two operations are separated by a discrete wavelength fraction; phase shift and attenuation result. These depend upon circumferential velocity, hence are worst at low rotational speed and small distance from the center of the record. The experimental study, therefore, is confined to 3331 r.p.m. recordings at various diameters, and the recorded velocity as a function of frequency and diameter is determined for needles with different lengths of dulling. The effect of amount of dulling on surface noise is determined, and a technique for comparing the perfection of action of cutting and burnishing is given. It is emphasized that for modern quality standards the length of dulling must be restricted and that the resulting increase in surface noise is not of great importance.

A Large Radius Stylus for the Reproduction of Lateral Cut Phonograph Records

John D. Reid

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 274-275 (1942); (2 pages)

Online Publication Date: 16 Jun 2005

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Tracing Distortion in the Reproduction of Constant Amplitude Recordings

Ludwig W. Sepmeyer

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 276-280 (1942); (5 pages)

Online Publication Date: 16 Jun 2005

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A Noise and Wear Reducing Phonograph Reproducer with Controlled Response

F. H. Goldsmith

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 281-283 (1942); (3 pages)

Online Publication Date: 16 Jun 2005

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The Correlation Between Elastic Deformation and Vertical Forces in Lateral Recording

S. J. Begun and T. E. Lynch

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 284-287 (1942); (4 pages)

Online Publication Date: 16 Jun 2005

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See Also: Erratum

Abstract Unavailable

The Recording Laboratory in the Library of Congress

Jerome B. Wiesner

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 288-293 (1942); (6 pages)

Online Publication Date: 16 Jun 2005

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Methods for Measuring the Performance of Hearing Aids

Frank F. Romanow

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 294-304 (1942); (11 pages)

Online Publication Date: 16 Jun 2005

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A hearing aid can be considered as a sound transmission system which is interposed in the path between the source of sound and the listener's ear. As such its performance can be judged by comparing the sound that reaches the ear first through the air path and then through the hearing aid. The experimental procedure to carry out this concept is, however, time consuming. To obtain a simple laboratory technique for comparative purposes, it is proposed, therefore, that the amplification of a hearing aid be measured by placing its microphone in a known sound field and observing the output of the receiver when terminated in an appropriate impedance. For an air conduction receiver this impedance takes the form of a closed cavity. For a bone conduction receiver the termination is an artificial mastoid. Since in a portable hearing aid compactness is desired, the undistorted pressure that can be developed by the set is limited in magnitude. Also the amplification is a function of the variation of the power supply voltages. Hence it is necessary that these characteristics be measured. As an illustration of the different factors involved characteristic curves for a recently developed vacuum tube aid are shown.

Lip Vibrations in a Cornet Mouthpiece

Daniel W. Martin

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 305-308 (1942); (4 pages) | Cited 3 times

Online Publication Date: 16 Jun 2005

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Directivity and the Acoustic Spectra of Brass Wind Instruments

Daniel W. Martin

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 309-313 (1942); (5 pages)

Online Publication Date: 16 Jun 2005

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Erratum: Phase Distortion in Electroacoustic Systems (J. Acous. Soc. Am. 13, 115, 1941)

Francis M. Wiener

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 317-317 (1942); (1 page)

Online Publication Date: 16 Jun 2005

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A Phonograph Pick‐Up of the Moving Coil Type (A)

Theodore Lindenberg, Jr.

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 330-330 (1942); (1 page)

Online Publication Date: 16 Jun 2005

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Since the earliest acoustic phonographs passed into history and vacuum tube amplification became a practical reality, an ideal pick‐up design has been the goal of recording engineers. This development has followed three basic types; magnetic, crystal and moving coil, and a new design of the latter forms the subject of this paper. Considering the physical mass of the moving elements of the three above‐mentioned types and their mechanical construction, the writer's design provides a considerable reduction of moving mass together with durable mechanical design. This reduction in mass, higher stylus compliance, lower stylus pressures, together with a unique “floating head” arm design, provide a frequency range and freedom from harmonic distortion which have been heretofore unattainable save with very fragile laboratory models. Inasmuch as the unit is a true generator, this paper also covers the design of a rather simple capacitance, resistance, equalizer to match output to the various recording characteristics in general use today.
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Properties of the Dulled Lacquer Cutting Stylus (A)

C. J. LeBel

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 330-330 (1942); (1 page)

Online Publication Date: 16 Jun 2005

Full Text: | Download PDF

Show Abstract
The recent improvement in disk recording standards is emphasized. The combined cutting and burnishing action of a standard lacquer cutting stylus is explained. It is emphasized that cutting and burnishing take place simultaneously (in terms of wave‐length) at low frequencies; but that at higher frequencies the two operations are separated by a discrete wave‐length fraction; phase shift and attenuation result. These depend upon circumferential velocity, hence are worst at low rotational speed and small distance from the center of the record. The experimental study, therefore, is confined to 33⅓ r.p.m. recordings at various diameters, and the recorded velocity as a function of frequency and diameter is determined for needles with different lengths of dulling. The effect of amount of dulling on surface noise is determined, and a technique for comparing the perfection of action of cutting and burnishing is given. It is emphasized that for modern quality standards the length of dulling must be restricted and that the resulting increase in surface noise is not of great importance.
FREE

A Noise and Wear Reducing Phonograph Reproducer with Controlled Response (A)

F. H. Goldsmith

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 330-330 (1942); (1 page)

Online Publication Date: 16 Jun 2005

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A replaceable phonograph needle having a large radius stylus, a spring mounting and controlled damping has been developed in cooperation with Mr. John Reid. Improved results are obtained in record and stylus wear, reduction of acoustic radiation and the ability to reproduce complex passages of large amplitude. In addition, this new needle affords protection against accidental damage to the stylus point and to the surface of the record. It is shown that by proper choice of constants it is also possible to eliminate compensating networks and thereby effect an increase in reproducer output. This device is in current production by the Webster Electric Company of Racine, Wisconsin, and is used on the Crosley radio phonograph combinations. (The presentation of this paper will be accompanied by demonstrations of the benefits obtained with the new needle using sound reproduction, oscillographic illustration and slides.)
FREE

A Large Radius Stylus for the Reproduction of Lateral Cut Phonograph Records (A)

John D. Reid

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 330-330 (1942); (1 page)

Online Publication Date: 16 Jun 2005

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This paper shows that novel and unexpected benefits are obtained by use of a stylus of sufficiently large tip radius to contact only the upper portions of the side walls of a laterally cut phonograph record groove. The benefits are: (a) an increase in high frequency output; (b) a decrease in acoustic radiation from the surface of the record; (c) an increase in record life; (d) an increase in stylus life; (e) a decrease in picked up scratch frown both new and worn records; (f) a decrease in stylus point pressure required for proper tracking. A stylus tip which will give this performance for the case of standard commercial records has a radius on the order of 4.2 mils or nearly double the radius of 2.3 mils heretofore thought most desirable. This device is in commercial use in conjunction with the Crosley radio‐phonograph combinations and is the subject of U. S. patent 2,251,204. In commercial use the large radius stylus is combined with a special spring mounting and drives a crystal cartridge. The spring mounted stylus was developed in conjunction with Mr. Frank Goldsmith and the additional benefits obtained thereby are explained in the preceding paper. (The presentation of this paper will be accompanied by demonstrations of the benefits obtained with the large radius stylus utilizing both sound reproduction and oscillographic illustration.)
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The Influence of Elastic Properties of Disk Material upon the “Pinch‐Effect” in Lateral Recording (A)

S. J. Begun and T. E. Lynch

J. Acoust. Soc. Am. Volume 13, Issue 3, pp. 330-331 (1942); (2 pages)

Online Publication Date: 16 Jun 2005

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It has been held that the properly designed lateral phonograph pick‐up should have incorporated between the stylus tip and the generating unit, an element which is flexible to vertical motion and does not generate voltages due to vertical excitation. This flexibility is supposed to reduce the mass forces generated by the “pinch‐effect” vertical accelerations to a minimum, and thus reduce groove and stylus wear and also harmonic distortions. It is shown, however, that the elastic properties of all common disk materials is such that the stylus rides in pockets in the groove walls, and these displacements or pockets have a value given by the stylus forces generated by the groove geometry. It is further shown that the “pinch‐effect” forces can be absorbed by the elastic properties of the record material without destructive forces. From this it appears that there is no practical necessity for providing the aforementioned coupling member between stylus tip and generating element in the lateral pick‐up.
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