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Journal of the Acoustical Society of America

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Jan 1936

Volume 7, Issue 3, pp. 167-239

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The Relation between Loudness and Masking (A)

Harvey Fletcher

J. Acoust. Soc. Am. Volume 7, Issue 3, pp. 238-238 (1936); (1 page)

Online Publication Date: 15 Jun 2005

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This paper describes the derivation of a formula for calculating the loudness of any sound from the masking audiogram obtained with the observer immersed in the sound. This formula contains a new function which is dependent only on the masking audiogram. This function was derived from the loudness function G(L). The calculations by this formula are very simple and give results which agree well with those observed.
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Change of Pitch with Loudness at Low Frequencies (A)

W. B. Snow

J. Acoust. Soc. Am. Volume 7, Issue 3, pp. 238-238 (1936); (1 page)

Online Publication Date: 15 Jun 2005

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The changes in pitch which result from changes in the loudness of low frequency tones were investigated for several frequencies between 75 and 1000 c.p.s. with a crew of 9 observers. The loudness levels covered the range 20 to 120, and both telephone receivers and a loudspeaker were used as sound sources. Fletcher's pitch standard, a pure tone of loudness level 40, was employed.
All consistent judgments gave pitch shifts downward with increasing loudness, but large differences between individuals were found. Two observers perceived no shifts at any frequency or loudness while three others experienced changes greater than 35 percent at the highest intensity. Appreciable changes with time in individual judgments were found. There appeared insignificant difference between data obtained with telephone receivers or with the loudspeaker. A set of contours of equal loudness level, plotted on coordinates frequency and pitch change in percent, is given. These curves show a pitch change small at 1000 cycles, increasing to maximum at a low frequency and decreasing for still lower frequencies. The frequency of greatest shift increased from about 100 cycles at small loudness to about 200 at loudness level 120.
The Appendix describes automatic test equipment that greatly simplified the testing routine and improved its accuracy.
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A Method for Obtaining Natural Directional Effects in a Public Address System (A)

R. D. Fay

J. Acoust. Soc. Am. Volume 7, Issue 3, pp. 239-239 (1936); (1 page)

Online Publication Date: 15 Jun 2005

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In studying the effects produced by two or more source simultaneously emitting the same sounds, it has frequently been noticed that all of the sound appears to come from the nearest source provided the difference in distances between the observer and the sources lies between fairly definite limits. A group address system was set up to utilize this effect in making it appear to the audience that the amplified sound of the speaker's voice came directly from his mouth. Excellent results were obtained, even with relatively great amplification, when the sound reproducing units were about 20 feet behind and 45 feet above the speaker.
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A Method for Maintaining in a Public Address System the Illusion that the Sound Comes from the Speaker's Mouth (A)

W. M. Hall

J. Acoust. Soc. Am. Volume 7, Issue 3, pp. 239-239 (1936); (1 page)

Online Publication Date: 15 Jun 2005

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As described in the paper by Professor Fay, it is possible to maintain the illusion that the sound comes from the speaker's mouth by arranging the reproducing system so that the original sound reaches the listener's ear before the reproduced. A study has been made of this effect to determine some of its limitations and possibilities.

Sound Reenforcing Systems

Harry F. Olson

J. Acoust. Soc. Am. Volume 7, Issue 3, pp. 239-239 (1936); (1 page)

Online Publication Date: 15 Jun 2005

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The inadequate speech power of the human voice in theaters and auditoriums is one of the most serious limitations to good hearing. The type of theater which suffers most from inadequate loudness of speech is, of course, the very large enclosed theater and the open air theater. Further in some instances the music furnished by an orchestra is of inadequate volume range to render full artistic interpretation. In these cases means are required for augmenting the intensity of the original sound. The systems for accomplishing this objective are termed sound reenforcing or public address systems. This paper describes the arrangement of the microphones, microphone mixing system and the loudspeakers for increasing the level of the original sound as well as obtaining uniform sound intensity in all parts of the theater. The use of directional microphones and loudspeakers minimizes difficulties due to feed‐back. Arrangements for outdoor sound reenforcing systems for various applications are discussed. Announce and call systems are discussed with respect to the arrangement of loudspeakers and microphone locations.

Sound Reenforcement—An Acoustic Problem

S. K. Wolf and G. T. Stanton

J. Acoust. Soc. Am. Volume 7, Issue 3, pp. 239-239 (1936); (1 page)

Online Publication Date: 15 Jun 2005

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This paper discusses the approach to the subject of public address as an acoustic problem.
The primary function of a public address system is to faithfully produce, at all points in the listening area, sound of adequate loudness as heard close to its origin. The attainment of this objective is discussed in terms of the acoustic factors involved and their relation to the physical design of the apparatus.
The first of the factors is the directional‐frequency characteristic of the loudspeakers involved, in terms of their relationship to the acoustic transmission of the auditorium. The tremendous complexity of computation of acoustic transmission requires, in the present state of the art, empirical determination of this factor by instrumental means. Since design limitations in the loudspeaker are such as to seldom permit securing exactly the frequency‐directional characteristic required, a modification in the characteristic of electrical energy input to the speaker must be made. The requirement of attaining adequate loudness may be limited by acoustic regeneration or “feedback.” A brief discussion of the controlling factors is included.

The Performance of a Public Address System as a Function of Auditorium Absorption

C. P. Boner

J. Acoust. Soc. Am. Volume 7, Issue 3, pp. 239-239 (1936); (1 page)

Online Publication Date: 15 Jun 2005

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This paper summarizes the work done in connection with public address systems at the University of Texas, particularly in Gregory Gymnasium, an auditorium of one million cubic feet capacity, seating eight thousand people. The results of sound pressure measurements are given, as they show the nature of absorption in the auditorium and the resulting effect on acoustic regeneration and the frequencies at which “singing” takes place. Methods of reducing acoustic regeneration are discussed, which, in the case of Gregory Gymnasium, permit the public address system to establish a sound pressure of approximately twenty bars in the rear of the room, with microphone on the stage and a small orchestra playing.
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