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Nov 1989

Volume 86, Issue S1, pp. S1-S125

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back to top Session N. Architectural Acoustics II: Acoustics in Performing Spaces
Contributed Papers
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Is diffusion in concert halls a property of the volume or of the surface? (A)

James B. Lee

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S34-S34 (1989); (1 page)

Online Publication Date: 13 Aug 2005

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For nearly a century, the principal concept of the theory of concert halls has been that of a nearly uniform field of energy, generated by many reflections, that varies but slowly with time. This supposed uniformity and isotropy gave rise to the term “good diffusion,” a property of the volume; it is difficult to quantify. An alternate approach is to apply the photometric concept of diffuse reflection at the surfaces: This is readily quantified, permits calculation of intensity at the audience, and posits nothing about the properties of the volume. Microcomputer programs to implement the concept are at hand and have been applied to a study of Boston Symphony Hall, renowned for its highly diffuse ceiling and walls. Modeling techniques, also borrowed from photometry, are available too: 1/50th scale architectural models are eminently suitable; note that models employing mirrors—specular reflectors—are not accurate representations of good concert halls.
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The organ as a teaching resource in architectural acoustics (A)

Bertram Y. Kinzey, Jr

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S34-S34 (1989); (1 page)

Online Publication Date: 13 Aug 2005

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The study of architectural acoustics must include an acquisition by students with limited or no musical background of a range of knowledge beginning with the harmonic structure of sound and its effect on timbre and continuing through an awareness of the ways, for better or worse, the architectural enclosure creates a reverberant field that affects various attributes such as blend, clarity, and fullness of tone and completes the musical sound that is heard. Aural experiences are essential if the student is to understand fully musical sound and the role of an architectural enclosure in its proper audition. The organ is an ideal instrument for demonstrations that give this experience. A series of live and recorded demonstrations using the organ is described which have been used over several years to show the relationship between music and architectural acoustics.
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Application of vector intensity techniques for the acoustical characterization of a baroque‐style Italian theater (A)

Domenico Stanzial, E. Carletti, I. Vecchi, and A. Fuschini

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S34-S34 (1989); (1 page)

Online Publication Date: 13 Aug 2005

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Results concerning acoustical measurements carried out in the Municipal Theater of Ferrara, built in 1790, are here presented. Recent restoration works replaced the original wooden stage. A model, which describes the enclosed space as a retroactive linear system, has been developed to characterize rooms acoustics. Modifications of the acoustic field, induced by the new stage, were measured by means of the following objective tests: evaluation of the theater transfer function having related input and output, respectively, defined by the free‐field acoustic power of a reference source and the measured power emitted by the same source placed on the stage surface; mapping of isointensity levels over the coupling area between stage and hall (proscenium plane); evaluation of acoustic‐intensity‐based transfer functions over a grid in the proscenium plane. A further description of the theater acoustics was obtained by intensity vector measurements over three parallel grids in the proscenium. Results of this additional characterization are presented as graphic views of acoustic intensity flow lines.
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Verification of Bergeron's analytical method applied to room acoustics (A)

Hidemaro Shimoda, Norinobu Yoshida, and Ichiro Fukai

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S34-S34 (1989); (1 page)

Online Publication Date: 13 Aug 2005

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Applicability of the Bergeron's method to room acoustics has been studied, and was found useful for a transient analysis in the time domain [J. Acoust. Soc. Am. Suppl. 1 84, S64 (1988)]. In this paper, a verification study of the proposed analytical method is presented. Transient time responses and reverberation times measured in a rectangular scale model were compared to the analytical results. The time responses at six positions in the room were observed by pulse excitation with 1/3‐octave‐band tone burst, and reverberation times were evaluated from these responses using Schroeder's integrated impulse method. Each time response at various points agreed very well with that of the scale‐model experiment and the average of calculated reveberation times also agreed favorably with the experiment.
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Temporal change in interaural cross‐correlation functions due to signal dynamics (A)

H. Yanagawa

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S34-S34 (1989); (1 page)

Online Publication Date: 13 Aug 2005

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Maximal values of transient interaural cross‐correlation functions (TRICC) for simple burst signals were used earlier to analyze temporal changes in spatial impressions such as sound image localization and subjective diffuseness. These temporal changes were found to correspond with subjective experiences [Yanagawa et al., J. Acoust. Soc. Am. 84, 1728–1733 (1988)], for the present study, a sound signal was chosen that is closer to transient sources such as music or voice. It consists of two bursts of white noise with a silent pause inbetween that is shorter than the reverberation time of the room. TRICC values at the rise of the second white noise signal were analyzed to see how they changed with the length of the pause and with room volume. It was found that a shorter pause causes the fall (reverberation) of the initial sound burst to overlap the second, so that TRICC values are smaller, but less so when the room is smaller. These results clarify how temporal changes in TRICC closely reflect differences in rooms with regard to ease of sound image localization.
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Separation of total transfer function phase into propagation and reverberant components (A)

Lan Liu and Richard H. Lyon

J. Acoust. Soc. Am. Volume 86, Issue S1, pp. S35-S35 (1989); (1 page)

Online Publication Date: 13 Aug 2005

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Previously reported theory of phase decomposition used the complex cepstrum to extract the all‐pass phase from the total phase of acoustical space transfer functions. The all‐pass phase is associated with the reverberant properties of two‐ and three‐dimensional spaces. The dereverberation of acoustical signals in such spaces can be accomplished by this separation. This paper describes the results of some recent experimental studies of sound propagation in one‐, two‐, and three‐dimensional spaces. A comparison of the expected and observed components of reverberant and propagation phase, with the results from these experiments, is presented.
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