Investigating the buildup of precedence effect using reflection masking

Jess Hartcher‐O'Brien, M. Buchholz, M. Buchholz
2006 Journal of the Acoustical Society of America  
Chair's Introduction-7:30 Invited Papers 7:35 2aAA1. Differences in dealing with the acoustics of large outdoor and indoor listening spaces. Daniel R. Raichel ͑Eilar Assoc. and the Graudate Ctr., CUNY, 2727 Moore Ln., Fort Collins, CO 80526, draichel@comcast.net͒ It was perhaps fortuitous that Wallace Clement Sabine's first consulting assignment from the Harvard Board of Overseers, the execution of which proved to be seminal in the history of architectural acoustics, entailed an indoor
more » ... The problems of dealing with outdoor performance areas are considerably greater than those encountered in indoor spaces. Indoor spaces provide surface reflections and absorption of sound, both of which can be manipulated through proper design to yield the desired results with respect to reverberation time and sound dispersion. In the case of outdoor performing areas, there are no reflective surfaces ͑except in the cases of certain amphitheaters͒, and the need for sound amplification is often necessitated. A reflective bandshell is generally required to direct the program material toward the audience. The lack of wall reflections tends to result in a lack of musical sonority that is usually present in a well-designed indoor auditorium. A number of specific problems with interior and outdoor spaces and modern approaches toward resolving acoustical problems of large listening areas will be discussed. 7:55 2aAA2. Prediction of reverberation by stochastic processes in a forest: Creation of reverberation in an outdoor performance space. Toshiki Hanyu and Katsuaki Sekiguchi ͑Nihon Univ., Narashinodai, Funabashi, Chiba, Japan, A forest is an outdoor space. For that reason, reverberation formulas of indoor spaces cannot be used when predicting forest reverberation. As a matter of fact, because the level decay curve of the reverberant sound produced in a forest is nonlinear, the concept of reverberation time is inapplicable. We clarified that reverberation of a forest is expressible as a Wiener process ͑Brownian motion͒, which is a stochastic process, and we derived the formula of reverberation of a forest based on that fact. In this study, Monte Carlo simulation was also carried out. Results clarified the following. ͑1͒ The energy decay curve of the reverberation sound of a forest becomes a straight line on the logarithmic scale of time and energy; its line gradient is Ϫ2. ͑2͒ At a point far from a sound source, the reverberant sound energy increases first and begins to decrease after some period. ͑3͒ When the mean-free path is short, the sound level of reverberation becomes high. Furthermore, we devised some methods of generating reverberation in outdoor space using the forest reverberation mechanism. For example, a proposed reverberation wall can produce reverberations using only one wall incorporating sound scatterers. 8:15 2aAA3. Large outdoor performance venues: Acoustical lessons learned. William J. Cavanaugh and K. Anthony Hoover ͑327F Boston Post Rd., Sudbury, MA 01776͒ The Tweeter Center for the Performing Arts ͑formerly Great Woods͒ in Mansfield, MA, off Interstate 495, midway between Boston and Providence, accommodates 19 900 patrons and offers 75 to 85 performances each year between 15 May and 15 October. The Pittsburgh Symphony Orchestra inaugurated Tweeter Center's first concert season in June 1986, and The Center hosted the PSO as its summer home for three additional seasons. The Center has hosted performances from solo comedians to symphonic orchestras and rock bands, featuring such diverse acts as the Boston Pops, James Taylor, Phish, and The Kinks. The acoustical lessons learned over two decades of operation are described. The Center has served as a model for the design and operation of facilities in the 20 000-capacity range, including the often difficult issues of controlling excessive amplified sound transmission to residential neighbors, as well as assuring good listening conditions for patrons and performers alike. 3052 3052 Fourth Joint Meeting: ASA and ASJ 8:35 2aAA4. Design of public address system for emergency evacuation in a tunnel. Sakae Yokoyama, Hideki Tachibana ͑Chiba Inst. of Technol., 2-17-1 Tsudanuma, Narashino-city, Chiba, 275-0016, Japan, sakae@iis.u-tokyo.ac.jp͒, Shinichi Sakamoto ͑Univ. of Tokyo, Meguro-ku, Tokyo, 153-8505, Japan͒, and Seiya Tazawa ͑Metropolitan Expressway Co. Ltd., Chiyoda-ku, Tokyo, 100-8930, Japan͒ As a means to improve speech intelligibility of a public address PA system for emergency evacuation announcement in a tunnel, the authors have been investigating the application of the successive time-delay technique and have performed the experiments in an actual tunnel. In the experiments, the effect of the technique has been examined by comparing the difference of speech intelligibility between the conditions with/without time delay. For the design of the PA system in a reverberant tunnel, four kinds of psychoacoustical experiments on speech intelligibility were performed in an anechoic room using the six-channel recording/reproduction technique and the following results have been obtained: ͑1͒ the successive time-delay technique is very effective to improve the speech intelligibility in a tunnel, ͑2͒ the system is considerably robust against the error in the delay time, ͑3͒ the speech intelligibility improves with the increase of the speech-rate but it should be suitable for such a tense situation as fire emergency, and ͑4͒ in order to further improve the speech intelligibility, it is necessary to control the reverberation in the tunnel by any sound absorption treatment. In this paper, the outline of the field experiment and the results of subjective experiments are introduced. 8:55 2aAA5. The Jay Pritzker Music Pavilion at Millennium Park, part 1: Design and construction. Richard Talaske ͑TALASKE, 105 N. Oak Park Ave., Oak Park, IL 60301͒ The acoustic and audio system design for the Pritzker Pavilion represents a leap forward in the outdoor listening experience. The venue offers superior sound experiences to audiences of 11 000 using audio reinforcement and acoustic enhancement systems to support all types of musical performances, particularly for the resident Grant Park Music Festival orchestra. With reliance on the audio systems to project and envelop the audience in sound, the design of the stage enclosure was able to focus on the acoustic quality for the ensemble, a rare opportunity in outdoor facilities. The stage enclosure design includes variable acoustic devices and has an emphasis on intraensemble communication. This presentation will discuss the design of the stage enclosure, the trellis-supported audio systems, and the ways in which the facility is used by resident and visiting musical performers. 9:15 2aAA6. The Jay Pritzker Music Pavilion at Millennium Park, part 2: Research and testing. Gregory Miller, Richard Talaske, The design of the Pritzker Pavilion includes a number of innovative acoustic and audio elements. Two of these elements, the resilient orchestra riser system and the acoustic enhancement system, will be discussed in this presentation. Research previously presented to the ASA ͓Hoffman et.al., 141st meeting of the ASA͒ was used in the design of the orchestra riser system at the Pritzker Pavilion. This presentation discusses the field tests that were conducted to assess vibration transfer across the surface of the riser system. Comparison is made to previous research and anticipated results. Subjective evaluations by orchestra members will also be discussed. The acoustic enhancement system is a specialized audio system, separate from the main reinforcement audio system, based on LARES digital signal processing and a distributed loudspeaker approach. Different settings have been developed over time to provide varying decay signatures that are employed on a music-program-dependent basis. Impulse response measurements were taken of unamplified sound, the reinforcement system, and the combination of the reinforcement system with the enhancement system. Testing was conducted with faculty and students from the University of Nebraska. 9:35 2aAA7. Acoustical design of the "Tenseishinbikai Hakko Shinden" Shrine in Shiga. Masayuki Ikegami ͑Dept. of Acoust Eng., Tech. Res. Inst., Obayashi Corp., 4-640 Simokiyoto, Kiyose City, Tokyo 208-8558, Japan͒ A shrine called the "Tenseishinbikai Hakko Shinden" was designed and constructed. It covers a large area and has seating for 3690 people. It is used mainly for religious ceremonies and occasionally for concerts. This report outlines its acoustical design and noise control measures. The acoustics design specifically addressed reverberation control appropriate for its use, in addition to echo-nuisance prevention. The flat fan shape of the building often engenders insufficient initial sound reflection and generates echoes. To avoid these problems, in consultation with the designer, an irregular reflective surface was used for the side walls, a rib-shaped acoustic absorption surface, and a folding-screen shaped diffusion surface was used for the rear wall. In addition to conventional machine room noise control, particular attention had to be devoted to glass walls, rain noise, etc. For the glass walls, the effects on the outside ͑sound generated in the event room͒ and the effects on the inside ͑outdoor traffic noise͒ had to be controlled. To control rain noise, the sound generated by rain on the metal roof had to be predicted; a suitable roof material was selected. 9:55 2aAA8. Sound around the New England Patriots' stadia. The New England Patriots wanted to build a new football stadium in Foxboro, MA, adjacent to the old one which would be demolished after the new one was opened. The Environmental Impact Statement ͑EIS͒ indicated that one benefit would be a 3.34-dB reduction of stadium noise at the nearest town line because the distance would increase by 980 ft. A procedure to test the resultant noise reduction was developed with keen interest from the Massachusetts Department of Environmental Protection. Touring rock 2a WED. AM 3053 Source-receiver distances in a large hall could be reduced by increasing the balcony overhangs, which, however, may cause insufficient acoustical energy for the under-balcony seats. Besides, the reduction in the sense of reverberation cannot be easily mitigated. In this research various design strategies, including utilizing the technique of a flying balcony, were examined in a 1550-seat hall with deep balcony overhangs. Both BEM simulation and scale model measurements were performed. Optimizing the profile of the under-balcony space and utilizing ceiling and side reflectors near the platform were effective in enhancing early reflection. This is especially meaningful for high-frequency string sounds that radiate against the ceiling. Opening the rear part of the balcony that formed a partially flying balcony could compensate late reflections. Preliminary scale modeling results showed that approximately 15% increase in early decay time can be achieved with carefully designed ceiling geometry when the opening area was only 7% of the overhang area. 3054 3054
doi:10.1121/1.4787437 fatcat:4h2rmntypzabhiivz7ddvu5uai