Sunday, October 6 9:00 am – 12:00 noon
SESSION F: ROOM ACOUSTICS AND SOUND REINFORCEMENT

Chair: Eric Benjamin, Dolby Laboratories, San Francisco, CA, USA

F-1 Factors Affecting Accuracy of Loudspeaker Measurements for Computational Predictions—Roger Schwenke, Meyer Sound Laboratories, Berkeley, CA, USA

The delay of a signal from the input terminals of a loudspeaker amplifier to the output terminals of a microphone can be represented as two parts: one from the electrical input to acoustical transmission and an acoustical propagation delay from some point on the loudspeaker to the microphone. For computational models of mixtures of loudspeakers to be correct, these delays must be measured accurately. It will be shown that temperature differences as small as 1 degree Celsius between measurements of two models of loudspeakers can cause significant differences in the predicted sound field. Though sound speed is much less sensitive to changes in humidity, the difference between assuming a typical humidity and assuming zero humidity (which is the norm) can be significant.
Convention Paper 5665

F-2 Systems for Stereophonic Sound Reinforcement: Performance Criteria, Design Techniques, and Practical Examples—Jim Brown, Audio Systems Group, Inc., Chicago, IL, USA

The delay of a signal from the input terminals of a loudspeaker amplifier to the output terminals of a microphone can be represented as two parts: one from the electrical input to acoustical transmission and an acoustical propagation delay from some point on the loudspeaker to the microphone. For computational models of mixtures of loudspeakers to be correct, these delays must be measured accurately. It will be shown that temperature differences as small as 1 degree Celsius between measurements of two models of loudspeakers can cause significant differences in the predicted sound field. Though sound speed is much less sensitive to changes in humidity, the difference between assuming a typical humidity and assuming zero humidity (which is the norm) can be significant.
Convention Paper 5666

F-3 Cable Impedance and Digital Audio—Stephen H. Lampen, David A. DeSmidt, Belden Electronics Division, San Francisco, CA, USA

One of the key differences between cable designed for analog signals and cable designed for digital signals is the impedance of the cable. Why is impedance important for digital but not for analog? What effect do impedance variations or mismatching have on digital signals? Can you use Category 5e or Category 6 computer cable to run digital audio? Can you use coaxial cable to carry digital audio? This paper addresses all these questions and also outlines the limitations of digital cable designs.
Convention Paper 5667

F-4 Limitations of Current Sound System Intelligibility Verification Techniques—Peter Mapp, Peter Mapp Associates, Colchester, Essex, UK

The role of emergency sound and voice alarm systems in life safety management has never been so important. However, to be effective, it is essential that such systems are adequately intelligible. Verification of system intelligibility is therefore assuming ever-greater importance. While a number of verification techniques are available, each is not without its drawbacks. The paper reviews the available methods and, using the results of new research, highlights areas of weakness of the current techniques.
Convention Paper 5668

F-5 Robustness of Multiple Listener Equalization with Magnitude Response Averaging—Sunil Bharitkar, Philip Hilmes, Chris Kyriakakis, University of Southern California, Los Angeles, CA, USA

Traditionally, room response equalization is performed to improve sound quality at a given listener. However, room responses vary with source and listener positions. Hence, in a multiple listener environment, equalization may be performed through spatial averaging of magnitude responses at locations of interest. However, the performance of averaging-based equalization, at the listeners, may be affected when listener positions change. In this paper, we present a statistical approach to map variations in listener positions to a performance metric of equalization for magnitude response averaging. The results indicate that, for the analyzed listener configurations, the zone of equalization depends on the distance of microphones from a source and the frequencies in the sound.
Convention Paper 5669

F-6 Coax and Digital Audio—Stephen H. Lampen, David A. DeSmidt, Belden Electronics Division, San Francisco, CA, USA

Coaxial cables have been used to run digital audio signals for many years, and have been added to the AES specifications (AES3-id). How is coax different from twisted pairs? What are the distance limitations? What trade-offs are made going from digital twisted pairs to digital coax? These questions are all answered in this paper including a discussion of baluns, which are used to convert from one format to the other.
Convention Paper 5670