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Nov 1980

Volume 68, Issue S1, pp. S1-S116

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back to top Session X. Architectural Acoustics III: New Discoveries of Wallace C. Sabine Papers. Time Delay Spectrometry and its Applications to Acoustical Measurements
Invited Papers
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A new discovery of Wallace Clement Sabine papers (A)

John W. Kopec

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S41-S41 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Twenty‐two correspondence files of Wallace C. Sabine, discovered recently at the Riverbank Laboratory, contain a rich supply of solutions to acoustics and noise control problems. Differing from his published papers (1) and notebooks (1), they are records of Sabine's extensive activities between 1909 and 1916 as an acoustical consultant. His projects covered auditorium acoustics, building noise transmission, the reduction of noise from industrial plants, and from machines. Of interest also are Sabine's findings on a constant‐power sound source, his part in the invention of acoustic tile, and his policies and ethical standards as an acoustical consultant.
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Some advanced applications of time delay spectrometry (A)

Richard C. Heyser

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S41-S41 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Time delay spectrometry (TDS) is a spread spectrum technique which utilizes a signal stimulus of the form exp[i θ (t)]. Delay tracking filters process the response of a system to that stimulus. The information extracted from these filters can either be of the more conventional type used for analysis, including the complex frequency response, complex time response, and complex cepstrum, or it can be of types not now readily obtained from conventional techniques. The choice of θ (t) with higher curvature than that of a quadratic phase chirp can allow direct measurement of dispersive propagation characteristics, including mode splitting into compressional and shear seismic waves which are created in the enclosure walls from air acoustic sources and which travel faster than sound in air to arrive at a listening location prior to the direct air path sound wave. Time varying systems, in which a boundary or scattering object move in the test space, can be isolated and measured by appropriate choice of TDS stimulus and filter. Four‐dimensional imaging of acoustic surfaces in a room is possible by coherent wavefront reconstruction from one or more sources processed by one or more microphone locations.
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Time delay spectrometry—An inquisitorial scrutiny of its value and use in architectural acoustics (A)

Cecil R. Cable

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S41-S41 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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Eight years of hands‐on experience in the application of time delay spectrometry to the field of architectural acoustics suggests that this exciting measuring system produces no magic numbers and no pat solutions to architectural problems. It does make available hard data on the behavior of sound within any enclosure and on reflections from and transmission through acoustical boundaries. Under discussion will be the use of this data; in its maximization and limitations as related to architectural design, in the testing of acoustical enclosures and materials and as an unprecedented learning experience.
Contributed Papers
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Energy time curve, etc, measurements of the decay rate, 60/T, and mean free path for the first 50 ms in small well‐damped rooms (A)

Don Davis

J. Acoust. Soc. Am. Volume 68, Issue S1, pp. S42-S42 (1980); (1 page)

Online Publication Date: 11 Aug 2005

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The temporal patterning, energy levels, and rates of absorption of early sound fields (first 50 ms) in small (under 10 000 ft3‐300 m3) well‐damped rooms is measured and evaluated. The rates of decay, 60/T, are measured via TDS‐ETC techniques for the first three reflected spectra in three planes and the mean free path they constitute is calculated from the measurement data. Remarks on the relevance of past theory with regard to present measurements will be offered.
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