Cost effective variable acoustics for multipurpose halls: 51 Walden Street.

51 Walden Street is a small multipurpose hall in Concord, Massachussets that serves for drama, symphony orchestra, concert band, and various other performance and rehearsal activities. As in many halls designed for a wide range of uses, limited passive variable acoustic provisions had been implemented with qualified success. However, recent measurements of the resulting acoustical conditions indicated that better acoustics required considerably more variability than possible using these simple techniques, which included varying the amount and positioning of sound absorption and reflecting surfaces within the hall. More complex passive variability, such as varying the room volume, was judged as not feasible because of the obvious architectural and cost limitations typically faced by community arts organizations. An experiment was carried out using a novel digitally controlled electroacoustic system to vary selected acoustical parameters, including reverberation time, early decay time, and clarity. Working with the major tenant groups during a season of rehearsals and performances, it was possible to correlate their judgments with objective acoustical measures. The flexibility and ease of electronically adjusting these parameters, as well as several new measures described, offered the opportunity to study their subjective significance efficiently.