Remedial acoustical design of a college band instrument rehearsal room modified because of asbestos treatment

Abstract

Removal of asbestos material from an instrument rehearsal room at CSU, Sacramento, including acoustical treatment led to a new design. The fix dramatically altered the characteristics of the room and resulted in unacceptable conditions. Temporary installation of heavy velour curtains made the room tolerable, but a permanent fix was sought. The room has nonparallel surfaces, large and long, barrel-shaped diffuser panels, hard walls and floor, and a mostly hard ceiling. Field measurements were made under three conditions to quantify the room’s acoustical conditions, including reverberation time and background sound levels. One-third octave band measurements were made from 12.5 to 10,000 Hz to cover all instruments and background sources. The 1-inch acoustical treatment first added to the room was not adequate to attenuate sound below 500 Hz, and insufficient to handle the high acoustical energy produced by the band. The echo between the floor and ceiling was very distinct, as neither surface had any treatment. Calculations using two different methods showed that substantial low-frequency sound absorption was required to reduce the sound at all frequencies to the design goal. The room is currently undergoing the modification, and results may be available at the time of the presentation.