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Nov 1975

Volume 58, Issue S1, pp. S2-S132

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back to top Session C. Architectural Acoustics I
Invited Papers
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Large room acoustics versus music (A)

Robert Weir, Jerry Garcia, Dan Healy, and Ron Wickersham

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S4-S4 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Too many large, music performance facilities around the country have acoustical characteristics which are not suitable for concert tours, particularly when electronic sound amplification is required. This paper concentrates on the acoustical problems affecting the musician and his performance. The various problems encountered and corrective procedures utilized by The Grateful Dead are discussed and include electronic instrumentation and measurement techniques, sound system applications, and room treatments.
Contributed Papers
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Practical problems in building acoustics (A)

Ewart A. Wetherill

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S4-S4 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Even for the small number of building projects in which they are involved, acoustics consultants may have little or no influence upon the matters that ultimately determine the success or failure of the design. Often important design decisions are made on the basis of any one of a dozen criteria without any consideration—or understanding—of their effect upon acoustics. During construction, the problems are compounded further by unknowing workmen. This paper reviews some of the prevalent situations that lead to acoustics problems. They can be broadly grouped into three categories: difficulties of interpretation, changes in materials and techniques, and getting things built as specified.
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Airborne noise requirements in building codes (A)

Theodore J. Schultz

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S4-S4 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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The business of devising a rating for airborne sound attenuation of building elements that closely corresponds to people's subjective evaluation of the acoustical performance, and of devising test methods for demonstrating satisfactory acoustical performance in a finished building, is very complicated indeed. Until recently, the tendency has been toward increasing complication of the test and rating procedure, in an attempt to make the single procedure account in near‐complete detail for the complexities of human response to noise. The result has been a test procedure that is too complicated for routine use in evaluating finished buildings. An alternative approach would be to divide the complicated task into a number of simpler tasks, each of which can be handled by relatively untrained staff, and to assure by regulation that all of the simpler tasks will be done for each evaluation. This paper proposes an example of the latter approach.
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Impact noise test method using a modified hammer machine (A)

Theodore J. Schultz

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S4-S4 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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The current national (ASTM E‐492) and international (ISO‐R140/R717) impact method involves the use of a standard hammer machine for evaluating the impact noise isolation of floor/ceiling structure. The method has been severely criticized on the ground that ratings based on the test data correlate poorly with the subjective judgments of people listening to real‐life impacts on the same floors. An alternative test method is proposed that uses a modified hammer machine whose internal impedance, intensity of impact and striking frequency simulate those of real footfalls; the new method involves reading the "peak" (i.e., short‐term rms) impact sound pressure levels in the receiving room, replacing the current practice of reading long‐term rms levels. No normalization for the sound absorption of the receiving room is required. Since the peak impact levels, particularly for floors with good impact isolation, are much higher than the long‐term rms levels usually measured, the interference of background noise is much less for the new method. These proposed changes, based on recent studies, are expected to lead to better correlation between the test data and subjective judgments of floors. On an experimental basis, it is proposed that the range of measurement be extended down to 40 Hz, because of the certainty that low‐frequency components are significant in the subjective evaluation of wood joist floors and the probability that peak levels are less susceptible to the problems of standing waves and lack of diffuseness than rms levels.
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Assisted resonance in the United States (A)

G. Berry

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S4-S5 (1975); (2 pages)

Online Publication Date: 11 Aug 2005

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The paper describes Assisted Resonance installations designed to provide variable reverberation time in two different types of situation. The first, in Concord, California, consists of a 3500‐seat pavilion with a backstage wall, but with the other sides open. The acoustic consultant has designed this space to provide ideal acoustic conditions for a full range of activity from drama through to symphonic presentations. The second, in Scottsdale, Arizona, is a smaller enclosed space but once again it is designed to accomodate a wide range of presentations. At the time of writing the abstract, the Concord installation is completed and believed to be successful but the Scottsdale installation is still under way and the outcome will not be clear until the paper is presented. The paper does not discuss the overall acoustic design, but is restricted to the role of Assisted Resonance, which deals with only one parameter, and the potential and limitations of the technique will be discussed.
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Textile industry weave room acoustical absorptive characteristics (A)

A. L. Cudworth and W. J. Hanson

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S5-S5 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Due to the complex nature of weave room equipment and materials, absorption coefficients of the various surfaces are difficult to calculate. Knowledge of this information could provide a basis for determining noise reduction due to architectural treatment as well as weave room noise level predictions. A typical weave room consists of masonry walls, wood ceilings, and either wood or concrete floors. Volumes are on the order of 400 000 to 900 000 cubic feet, and surface areas 60 000 to 140 000 square feet. Temperatures of 70° to 80° Fahrenheit, and relative humidities approaching 70% are not uncommon. Because of the unusual room proportions, for acoustic calculation purposes, a weave room is essentially two horizontal parallel planes. Reverberation time (decay rate) measurements were made in several weave rooms, and absorption coefficients calculated. Assuming known absorption coefficients of walls and ceiling, and accounting for high‐frequency attenuation due to relative high temperature and humidity, floor‐machine absorption coefficients have been calculated. Additional tests were conducted to determine decay with distance effects. A single source (fly shuttle loom) noise level was measured at various distances both along and across the weavers alley. This was done in two weave rooms, one with concrete floors and the other with wood.
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Acoustical environment in open plan office—the state of the art (A)

D. A. Harris

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S5-S5 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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ASTM E‐33.04C Subcommittee on Environmental Acoustics, Applications Subcommittee Task Force on Open Office Acoustics has prepared a publication titled, “Acoustical Environment in Open Plan Office—The State of the Art.” The purpose is to “assemble and explain responsible references to the state of the art.” Principles gathered to prepare this paper will be used to develop “applicable ASTM Standards and Recommended Practices.” The paper deals with the “acoustics of an open plane office in a manner that will clarify the basic acoustical principles and help designers and architects to achieve an acceptable and flexible environment.” Items covered include the nature of the sound field, speech communication versus privacy, attainment of privacy, ceiling screen and masking sound effectiveness, testing, and design parameters. A summary of the paper will be presented.
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Ceiling baffles for the remodeled open plan office (A)

D. A. Harris

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S5-S5 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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Achieving speech privacy in the remodeled or renovated open plan office space is usually complicated by the need to retain ceiling assembly fire resistant properties. The designer has few alternatives from which to choose. He may either install ceiling baffles beneath the existing fire‐rated assembly or remove the entire ceiling, lights, air terminals, and board, and install a new one. A sprinkler system may also be required. The expense and disruption of the latter solution poses a monumental obstacle. Acoustical properties of ceiling baffles have been evaluated by both objective and subjective tests. Although the baffles are not as efficient as recently developed open plan office ceiling systems, they can satisfy minimal speech privacy criteria. Design of both the baffle and their array is critical. To support these conclusions, test data and evaluation techniques will be presented.
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Another look at the acoustics of open plan schools (A)

David P. Walsh

J. Acoust. Soc. Am. Volume 58, Issue S1, pp. S5-S5 (1975); (1 page)

Online Publication Date: 11 Aug 2005

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The open plan school has been with us now for over ten years, and the number of these schools being built per year is still on the increase. However, the acoustical environment of these spaces has received criticism with regard to high noise levels which result in annoyance, distraction, and speech interference. Even though the usage of open plan school spaces is quite different from that of open plan offices, the acoustical design recommendations for schools have generally been based on requirements for open plan offices. It appears that other considerations should be investigated for defining an acoustical environment acceptable for educational purposes. Our work has concentrated primarily on noise levels and annoyance in open plan classrooms. Direct relationships between noise levels, class size, student age level, and room finish treatments have been developed from extensive measured data. The subjective factor of annoyance has also been investigated and is related to background noise level and peak level fluctuations. Further investigations on the effects of room shaping are discussed as are statistical distributions of class noise.
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