August
Meeting Notice
August 2003 Meeting Notice
| Subject: | Measurement and auralization of 'moving' late reverberation |
| Speakers: | Durand Bengault , NASA Ames Research Center |
| Place: | Cogswell College, Sunnyvale |
| Time and Date: | August 20th, 7:30 PM (refreshments at 7:00 PM) |
The acoustical characterization and auralization of a large rectangular space with uniformly distributed absorption is facilitated by a predictably linear reverberant decay of decibel sound pressure level. By contrast, music is often performed in large spaces with irregular shapes that yield correspondingly irregular reverberant decays. A contributing factor is "coupled space" effects where the several reverberant decays occur simultaneously. When the mean free path for reflections is relatively large, as in a cathedral, temporal thresholds can be exceeded to the point where it is possible to hear spatially separated decays. The phenomenon of a slow amplitude modulation between separate locations can be described as "moving" late reverberation, which is audible, e.g., in a cathedral when a organ note is stopped. Measurements of this phenomenon were made in San Francisco's Grace Cathedral, a French Gothic-style Episcopal church, using multiple microphone impulse response recordings. Data on the temporal-spatial diffusion of reverberation from various spatial perspectives is presented, along with sound examples. Implications for auralization are discussed. Although not manipulated directly by the composer, performance space acoustics contribute to the spatial component of musical listening and musical composition.
Durand R. Begault Ph.D. (AES Fellow, 2002) is recognized worldwide within the acoustic and psychoacoustic community as an important figure in the field of virtual acoustic 3-D audio systems and displays. He has been associated with the Human Information Processing Research Branch of NASA Ames Research Center, located at Moffett Field in the Silicon Valley, since 1988. His peer-reviewed journal publications, patents, and books are cited in 57 US patents, and over one hundred scientific and engineering journal publications. His 1994 book "3-D sound for virtual reality and multimedia" sold over 3000 copies; he is also author of an interactive CD-ROM on computer audio production published by Academic Press, and of chapters in several acoustic and virtual environment reference books. Dr. Begault's research activities include development and evaluation of new audio and multi-modal technologies for aeronautic and space applications. These technologies involve psychophysical evaluation of spatial hearing, speech intelligibility, and performance in virtual environment systems; room acoustic analysis and simulation; and improvement of communications and warning systems. He is also active as an expert witness and acoustical consultant, and serves as Director of the Audio Forensic Center, Charles M. Salter Associates, San Francisco. He is a member of the Acoustical Society of America, the Audio Engineering Society, and the Institute of Noise Control Engineering. His activities at AES include the organization of many workshops and paper sessions, chairing of the Technical Committee on Perception and Subjective Evaluation of Audio Signals, and membership on the AES Journal's review board since 1993.
Directions
From the East Bay - Take 880 to 237 west. Exit on Mathilda Ave. north. Turn right on the frontage road and then left onto Bordeaux Drive. The meeting is in the auditorium.
From the Peninsula - Take 101 to 237 east. Exit on Mathilda Ave. north. Turn right on the frontage road and then left onto Bordeaux Drive. The meeting is in the auditorium.