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Journal of the Acoustical Society of America

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Apr 1936

Volume 7, Issue 4, pp. 242-305


The Beginnings of Architectural Acoustics

Paul E. Sabine

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 242-248 (1936); (7 pages)

Online Publication Date: 15 Jun 2005

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Abstract Unavailable

The Absorption of High Frequency Sound in Oxygen Containing Small Amounts of Water Vapor or Ammonia

Vern O. Knudsen and Leonard Obert

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 249-253 (1936); (5 pages) | Cited 1 time

Online Publication Date: 15 Jun 2005

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Abstract Unavailable

Elastic Impact of a Pianoforte Hammer

R. N. Ghosh

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 254-260 (1936); (7 pages)

Online Publication Date: 15 Jun 2005

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Abstract Unavailable

Method for Measuring Sound Isolation, in Particular of Impact Sound

F. M. Osswald

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 261-264 (1936); (4 pages)

Online Publication Date: 15 Jun 2005

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Abstract Unavailable

A New Treatment of the Horn‐Diaphragm Coupling Chamber for Receiver Measurements

C. K. Stedman

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 265-270 (1936); (6 pages)

Online Publication Date: 15 Jun 2005

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A loudspeaker may be tested by removing its horn and loading it acoustically with an air column of variable length in a closed tube. In this way one can measure the acoustic impedance of the horn and the sound power output of the speaker, under the assumption that the air chamber in front of the diaphragm can be regarded as an addition to the tube of an equivalent length r determined by experiment. Under this assumption the air load impedance ZA at the diaphragm is given by ZA  =  −j(A12/A2)ρc cot kx where A1 is the diaphragm area, A2, the cross section of the tube, and x the total length, i.e., actual length plus r. An analytical treatment leads to the formula
math
. Eq. (1) leads to correct results for the measurement of acoustic impedance of the horn and sound power output, but cannot be extended to determine the mechanical impedance of the diaphragm. Eq. (2) is the basis of a new treatment which is more general. It is expressed in terms of a parameter r which can be calculated theoretically at low frequencies, or determined empirically at higher frequencies. The theory has been verified experimentally.

Measurement of Speed Fluctuations in Sound Recording and Reproducing Equipment

Edward W. Kellogg and Adolph R. Morgan

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 271-280 (1936); (10 pages)

Online Publication Date: 15 Jun 2005

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High quality reproduction of recorded music is possible only if the speeds of recording and reproducing machines are maintained constant within very narrow limits. As improvements are made in these machines greater refinement in measurement of the variations is required in order that the progress may continue. The development of an improved “Wow‐meter” for such measurements is described, and various alternative schemes are discussed. The securing of a standard record, itself sufficiently free from imperfections, presents one of the most serious difficulties. For testing turntables a toothed steel wheel was built, in which special precautions were taken to minimize indexing and other possible errors. The current generated by means of this wheel is supplied to an electric circuit so arranged that variations in frequency cause deflections of a galvanometer, which are registered on a photographic film. The principle employed, namely, a resonant circuit slightly off tune, has been used in earlier devices. In the meter described a push‐pull arrangement has been adopted to reduce the likelihood of errors due to variations in voltage. A frequency meter of this type has certain inherent limitations in its ability to register very rapid fluctuations. Certain measures have been adopted to make the meter satisfactory in this respect, and the possibility of going further in this direction if necessary is given consideration.

A Technique for Studying the Efficiency of Panel Damping Materials

J. S. Parkinson and P. O. Young

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 281-286 (1936); (6 pages)

Online Publication Date: 15 Jun 2005

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Abstract Unavailable

The Transmission of Sound Through Sea Water. II

Herbert Grove Dorsey

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 287-299 (1936); (13 pages)

Online Publication Date: 15 Jun 2005

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The Calibration of Microphones

J. Acoust. Soc. Am. Volume 7, Issue 4, pp. 300-305 (1936); (6 pages)

Online Publication Date: 15 Jun 2005

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The American Standards Association Sectional Committee Z‐24 on Acoustical Measurement and Terminology has under it a Subcommittee on Fundamental Sound Measurements. The Subcommittee during the past few years has been considering definitions and test procedure pertaining to the calibration of microphones. The following report is the result of its work. At a recent meeting of the Sectional Committee it was voted to submit this work to the interested scientific bodies for publication in their journals with the thought of promoting constructive criticism and discussion. The Subcommittee made use of considerable material from the tentative report of the I.R.E. Standards Committee on Electro‐Acoustic Devices, and this is gratefully acknowledged.
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