Volume 121, Issue 4, April 2007
Index of content:
- ARCHITECTURAL ACOUSTICS 
Acoustic diffraction effects at the Hellenistic amphitheater of Epidaurus: Seat rows responsible for the marvelous acoustics121(2007); http://dx.doi.org/10.1121/1.2709842View Description Hide Description
The Hellenistic theater of Epidaurus, on the Peloponnese in Greece, attracts thousands of visitors every year who are all amazed by the fact that sound coming from the middle of the theater reaches the outer seats, apparently without too much loss of intensity. The theater, renowned for its extraordinary acoustics, is one of the best conserved of its kind in the world. It was used for musical and poetical contests and theatrical performances. The presented numerical study reveals that the seat rows of the theater, unexpectedly play an essential role in the acoustics—at least when the theater is not fully filled with spectators. The seats, which constitute a corrugated surface, serve as an acoustic filter that passes sound coming from the stage at the expense of surrounding acoustic noise. Whether a coincidence or not, the theater of Epidaurus was built with optimized shape and dimensions. Understanding and application of corrugated surfaces as filters rather than merely as diffuse scatterers of sound, may become imperative in the future design of modern theaters.
Measurement and prediction of speech and noise levels and the Lombard effect in eating establishments121(2007); http://dx.doi.org/10.1121/1.2535571View Description Hide Description
Measurements made of the acoustical characteristics of, and occupied noise levels in, ten eating establishments are described. Levels to which diners and employees were exposed varied from 45 to . From these levels and diner questionnaire responses, the number of customers present and average noise levels to which individual diners were exposed during their visits were estimated. These data, assumptions about the number of talkers per customer, and classical room-acoustical theory were used to deduce talker voice output levels. These varied from slightly above “casual” to “loud.” An iterative model for predicting speech and noise levels in eating establishments, including the Lombard effect as described by a new, proposed model, was developed. With the measurednoise levels as the target for prediction, optimization techniques were used to find best estimates of unknown prediction parameters—such as those defining the Lombard effect, the number of talkers per customer, and the average absorption per customer—with highly credible results. The prediction algorithm and optimal parameters constitute a novel model for predicting speech and noise levels—and thus speech intelligibility—in eating establishments, as a function of the number of customers, including a proven, realistic model of the Lombard effect.