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Journal of the Acoustical Society of America

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Feb 1970

Volume 47, Issue 2A, pp. 399-450


FOREWORD

William J. Cavanaugh

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 399-400 (1970); (2 pages)

Online Publication Date: 03 Aug 2005

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Model Testing of Auditoriums

Vern O. Knudsen

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 401-407 (1970); (7 pages)

Online Publication Date: 03 Aug 2005

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This report first reviews the history of model testing as an aid to the designing of auditoriums, beginning in 1913 with Sabine's spark photography [W. C. Sabine, “Theater Acoustics,” Amer. Architect. 104, 257 (1913)] and eventuating with the more sophisticated Spandock three‐dimensional models [F. Spandock, “Akustiche Modellversuche,” Am. Physik 20, 345–60 (1934)] scaled down to 1:10 and 1:5, including models with improvements by Japan's NHK Laboratories. It also reviews the two‐dimensional optical model tests we use at UCLA [as developed by R. W. Leonard “Simplified Optical Modeling for Auditoriums,” J. Acoust. Soc. Amer. 26, 937 (A) (1954)], which are expedient for determining approximately optimal shapes in plan and sections, followed, when deemed necessary, by tests of three‐dimensional models (optical and acoustical) that range in scale from 1:1 to 1:4, for critical (often repeated) segments of walls and ceiling, and down to 1:24, for the walls, floor, and ceiling, which can be examined separately and as progressively assembled into the complete model of the auditorium. Examples are presented of procedures and findings in connection with the acoustical designing of several multipurpose auditoriums and a theater in the round (220°) with thrust stage. Acoustical model testing reveals diffraction effects and echoes (or their absence) and helps in the designing of auditoriums that optimize early reflections, diffusion, reverberation, and sound‐level distribution.

Acoustical Criteria for Auditoriums and Their Relation to Model Techniques

Vilhelm Lassen Jordan

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 408-412 (1970); (5 pages) | Cited 2 times

Online Publication Date: 03 Aug 2005

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The first step in using model technique as a design tool is to establish a quantitative criterion (besides reverberation time). “Early to reverberant energy,” “steepness,” and “initial reverberation time” or “early decay time” (EDT) must be considered the most relevant factors, from aspects such as: (1) simplicity of measurement, (2) correlation with subjective assessments, and (3) possibility of comparing values obtained in scaled models with values obtained in full‐size halls. Measured values of EDT may be applied either by calculating the inversion index, i.e., the average value in the audience area of a hall divided by the average value in the stage area, or by comparing values of EDT measured in different locations of a model (or a hall) with values of average reverberation time. These techniques have been applied in a number of 1:10 scale models and, also, in some completed halls.

Instrumentation for Acoustic Modeling

B. G. Watters

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 413-418 (1970); (6 pages)

Online Publication Date: 03 Aug 2005

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Acoustic models are usually built so that one can make the same kind of measurements he would make if the full‐sized space or structure were available. Thus, much of the instrumentation needed for model work is the same as that used to evaluate completed projects. Other instruments must be high‐frequency analogs of conventional equipment in order to accommodate the model's frequency and time‐scale factor. This paper deals with instrumentation and techniques that have proven useful in acoustic models with scale factors ranging from about 1:3 to 1:24. Suitable high‐frequency microphones, spark‐discharge sound source, cathode‐ray‐tube “graphic level recorders,” and similar equipment are discussed.

Model Techniques in Architectural Acoustics

Paul S. Veneklasen

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 419-423 (1970); (5 pages)

Online Publication Date: 03 Aug 2005

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Sound sources, microphones, detection, and display are described for the modeling methods for both the steady‐state and transient types of testing. The methods have been refined for excellent precision for determining diffracted sound levels around complicated building structures, and for studying echograms within proposed auditorium designs so as to optimize envelopmental sound. Examples and quantitative results are presented for many types of applications.

Digital Simulation of Sound Transmission in Reverberant Spaces

M. R. Schroeder

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 424-431 (1970); (8 pages) | Cited 2 times

Online Publication Date: 03 Aug 2005

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Digital computers, through their capability for accurate simulation of complex phenomena, have permitted new insights into a number of important problems arising in sound transmission in reverberant spaces: (1) Reverberation theories, based on the geometrical acoustics, are being refined by ray‐tracing studies on digital computers. These studies have revealed significant discrepancies in existing reverberation‐time formulas and unexpected large dependencies of the decay rate on the shape of the enclosure and the distribution of sound‐absorbing materials. (2) Starting with reverberation‐free speech or music signals as inputs, computers can add echoes and reverberation with specified delays, spectral content, and decay characteristics. The computer produces several output signals that—when radiated from loudspeakers in an anechoic chamber—produce, at a listener's ears, sound‐pressure waves resembling those in real halls. To ensure “externalization” and proper directions of echo arrivals, the computer program is based on the measured sound diffraction around the listener's head. This digital simulation method is useful to “preaudit” architectural designs before construction and to investigate subjective correlates of a wide variety of reverberation processes. (3) Digital computers have made possible the simulation of frequency and space response of stationary sound fields and the calculation of their statistical properties. These properties are important for the design of electroacoustic systems and the evaluation of measurements in reverberant enclosures.

Polarity Coincidence Arrays

C. S. Clay

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 432-434 (1970); (3 pages)

Online Publication Date: 03 Aug 2005

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The purpose is to examine the performance of a multiple polarity signal‐processing system for an array having a small number of channels. The system has a narrow directional response and small side lobes for CW signals. In the m‐channel system, the instantaneous signals are sampled to determine the sign of the signals. If all m channels have the same sign, the output is 1 and otherwise the output is 0. The system performance is measured by the ratio of the mean output of system sN to the standard deviation of the output σN. Gaussian noise is assumed to be in each channel and is uncorrelated between channels. At small input‐signal to noise‐power ratios, sN/σN was proportional to the input‐signal to noise‐power ratio, N½ and f(m), where N is the number of independent observations and f(m) is a system function. f(m) has a maximum value at m = 6. The response of a six‐receiver array was simulated on a delay line. The signals were delayed the times 0, T, 2T, 4T, 7T, and 13T. For a CW signal, the output was 1 at the frequency T−1, and the null‐to‐null width of the main lobe was (15T)−1. The side lobes were less than 0.1.

Use of a Two‐Dimensional Array to Receive an Unknown Signal in a Dispersive Waveguide

C. S. Clay and M. J. Hinich

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 435-440 (1970); (6 pages) | Cited 1 time

Online Publication Date: 03 Aug 2005

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A relatively simple method is discussed for estimating the phase velocity and direction of an unknown plane‐wave signal, propagating across two‐dimensional array in a dispersive waveguide. The finite Fourier transform is applied to the output signal of each sensor, and the phases of the smoothed frequency components calculated. The phases of the components are linearly regressed on sensor positions to produce estimates of the wave slowness components. Neither the phase nor group velocity dispersion curves need to be known, except for upper and lower estimates of the range. By smoothing over frequency and transforming, estimates are obtained of the direction and phase velocity of the signal. The precision of estimates depends on the signal‐to‐noise ratio, the square root of the number of sensors, and the number of wavelengths that fall in the array. Each frequency is treated separately, so that the direction and phase velocity are obtained as a function of frequency. Since the individual frequency components of the signal are separated, the signals observed on a large array can be combined, even though the dispersion is appreciable over the array. For good signal‐to‐noise power ratios, the dispersion curves are a direct result from the analysis.
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On the Energy Transported with a Sound Pulse

Robert W. Young

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 441-442 (1970); (2 pages) | Cited 2 times

Online Publication Date: 03 Aug 2005

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Definitions of Fourier pressure spectrum level and integrated band pressure level are proposed for engineering description of the spectra of sonic booms and explosive sounds, and relations to specific energy spectral density are demonstrated.
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A PROCEDURE TO COMPUTE THE DEPTH OF A PRESSURE‐SENSING DEVICE

Volker Graefe and Richard Latham

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 443-444 (1970); (2 pages)

Online Publication Date: 03 Aug 2005

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A method is described to take into consideration the variability of the specific volume of seawater when determining the depth of an instrument from the in situ pressure. The method is sufficiently accurate to eliminate all errors in the depth determination other than the error of the pressure sensor itself.

EARPHONE SYSTEM FOR HUMAN INFANTS

Philip Peltzman, Alan Bass, and David Manchester

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 444-447 (1970); (4 pages)

Online Publication Date: 03 Aug 2005

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A condenser microphone‐driver system has been designed specifically for use as an infant earphone. A simple economical negative feedback amplifier compensates for the distortion of the condenser microphone when used as an earphone. The physical properties and unique advantages of the insert ear tubes present no apparent discomfort to a sleeping or awake infant, afford a measure of sound pressure generated in the ear canal, and permit a wide latitude of head movement.

THE PEPSI‐COLA PAVILION AT OSAKA: A RESULT OF COLLABORATION BETWEEN ARTISTS AND ENGINEERS

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 447-448 (1970); (2 pages)

Online Publication Date: 03 Aug 2005

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NOISE IS NOT NECESSARY

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 448-448 (1970); (1 page)

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COCKPIT NOISE ENVIRONMENT OF AIRLINE AIRCRAFT

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 449-449 (1970); (1 page)

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Calibration and Working Condition of 100 Audiometers

W. G. Thomas, M. J. Preslar, R. R. Summers, and J. L. Stewart

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 449-450 (1970); (2 pages)

Online Publication Date: 03 Aug 2005

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Acoustic‐Gravity Waves in the Atmosphere, Symposium Proceedings

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 450-450 (1970); (1 page)

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NAVY NOISE CONTROL CONFERENCE

J. Acoust. Soc. Am. Volume 47, Issue 2A, pp. 450-450 (1970); (1 page)

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