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May 1987

Volume 81, Issue S1, pp. S1-S100

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back to top Session M. Architectural Acoustics II: Computers in Architectural Acoustics
Invited Papers
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Computers in architectural acoustics (A)

Manfred R. Schroeder

J. Acoust. Soc. Am. Volume 81, Issue S1, pp. S30-S30 (1987); (1 page)

Online Publication Date: 13 Aug 2005

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Already in the 1950s difficult problems in acoustics were being successfully attacked by computer simulation. One of the first digital simulations of a signal processor was that of an artificial reverberator to produce natural‐sounding reverberation. Other early applications of computers used Monte‐Carlo simulations to study random wave interference in enclosures. Later, computers were used extensively in the measurements in Philharmonic Hall (now Avery Fisher Hall) in New York City. This work also led to the development of new methods for measuring reverberation time. In the 1970s, with the support of the German Science Foundation, a large number of concert halls were investigated with the help of sound field reproduction and multidimensional scaling methods using digital computers. The most important new parameter emerging from these studies was “interaural dissimilarity.” The diffusely reflecting surfaces called for by these results are based on number‐theoretic principles [M. R. Schroeder, Number Theory in Science and Communication (Springer, New York, 1986) 2nd enlarged ed.]. Computers have also been used to crack complicated integral equations to yield accurate relationships between reverberation time and sound absorption that are sensitive to absorber location and sound diffusion.
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Prediction of point‐to‐point acoustic transfer function within a three‐dimensional enclosure using ray path methods (A)

James L. Wayman, Robert V. Esperti, and James P. Vanyo

J. Acoust. Soc. Am. Volume 81, Issue S1, pp. S30-S30 (1987); (1 page)

Online Publication Date: 13 Aug 2005

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This report details a study conducted for the General Motors Corporation to construct a model for predicting point‐to‐point acoustic transfer functions in automobile passenger compartments for the purpose of predicting entertainment system performance. The model is based on ray path methods and includes effects of curved enclosure surfaces and complex boundary impedances. Comparisons between model results and experimentally obtained transfer functions are promising.
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Determination of the direction, time, and intensity of arrival of acoustic signals (A)

Farrel M. Becker

J. Acoust. Soc. Am. Volume 81, Issue S1, pp. S30-S30 (1987); (1 page)

Online Publication Date: 13 Aug 2005

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There is currently much interest in lateral reflections in concert halls. Attempts to quantify lateral reflections have, up to now, been limited. Lateral energy ratios have been measured using a bidirectional microphone. This technique lacks the resolution necessary to investigate direction other than side to side versus front to back. A new technique, known as the polar energy time curve, will be presented. Utilizing special software for equipment already in common use, this technique extracts accurate directional information from four energy time curve (or impulse response) measurements made with an ordinary cardioid microphone. The direction of arrival versus time or intensity is displayed in polar form. The time, intensity, and exact angle of arrival may be determined in any plane of interest. Three‐dimensional displays of energy arrival are also possible. Conventional lateral energy fractions, as well as other quantities, may be computed.
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Evaluation of room speech transmission index and modulation transfer function by the use of time delay spectrometry (A)

D. B. Keele, Jr. and Donald Eger

J. Acoust. Soc. Am. Volume 81, Issue S1, pp. S31-S31 (1987); (1 page)

Online Publication Date: 13 Aug 2005

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The literature shows that the modulation transfer function (MTF) and speech transmission index (STI) can be computed from the squared impulse response of a linear passive system. This paper describes an extension of this method to measurements of systems using time delay spectrometry (TDS). The new method makes use of both the real and imaginary parts of the complex analytic impulse response of the system (the energy‐time response). This allows more accurate determinations of STI and MTF because the calculations are based on a measurement that more closely follows the true energy decay in the room. The method requires fewer samples of the room's sound field and less spatial averaging to yield a given accuracy.
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Criteria and analysis for fan/floor vibration isolation in elevated mechanical rooms (A)

Angelo J. Campanella

J. Acoust. Soc. Am. Volume 81, Issue S1, pp. S31-S31 (1987); (1 page)

Online Publication Date: 13 Aug 2005

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In selecting isolators for fans and other mechanical equipment mounted on elevated mechanical room floors, it is necessary to know the degree with which their vibrations will affect the occupants of the floor on which it is mounted, as well as the floor below. A computational procedure was developed based on a two degree of freedom model representing the resulting floor motion for known masses, resonances, and damping of the floor and fan mount. A computational criterion was developed for vibration input and human vibration tolerance based on values commonly found in the literature. A FORTRAN program featuring interrogatory input prompts and a screen graphics output of the floor vibrational velocity over the frequency band of concern executes in about 30 s. With this tool, one can immediately judge the effectiveness of various fan masses and spring constants. Two case studies are discussed.
Contributed Papers
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A presentation of acoustical impulse responses with an analog‐to‐digital converter (A)

Edward G. Clautice

J. Acoust. Soc. Am. Volume 81, Issue S1, pp. S31-S31 (1987); (1 page)

Online Publication Date: 13 Aug 2005

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A research program in architectural acoustics at the University of Florida has been using analog electrical equipment to process signals. An analog‐to‐digital converter was acquired to allow faster and better signal analysis. Several computer programs were written that control the analog‐to‐digital converter and subsequent processing of the digital data. The ability of the analog‐to‐digital converter to analyze some properties of known signals was evaluated. The analog‐to‐digital converter was then used to evaluate signals from magnetic tapes which had the recorded acoustical impulse response from several positions in a 1500 seat auditorium. The processing programs were used to produce echograms. Those digital echograms were able to duplicate the echograms produced by the laboratory's existing instrumentation in terms of the relative location of events in time and the decay process through time. The process and results of this research will be surveyed.
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The use of an IBM personal computer (PC) for performing room acoustics measurements (A)

Richard H. Talaske

J. Acoust. Soc. Am. Volume 81, Issue S1, pp. S31-S31 (1987); (1 page)

Online Publication Date: 13 Aug 2005

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The general acceptance of the PC microcomputer and the subsequent availability of additional hardware and software have offered researchers and practitioners some formidable tools for acoustical investigations. Using an IBM portable PC, ILS signal‐processing software, and additional signal gathering and signal conditioning equipment, an inexpensive and portable room acoustics and data collection system was developed for the purpose of investigating the acoustics of theaters, concert halls, and other assembly spaces. This system will be described, and the results of data will be presented and discussed.
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