ASA 125th Meeting Ottawa 1993 May

3pAA9. Performance of a large new anechoic chamber at the Canadian Bureau of Radiation and Medical Devices.

S. H. P. Bly

Bureau of Radiat. and Med. Devices, 775 Brookfield Rd., Ottawa, ON K1A 1C1, Canada

A. D. Lightsone

Valcoustics Canada Ltd., Toronto

T. G. Hewlings

J-L. Lourador

Resonance TJL, Montreal

The large new anechoic chamber is to be used for health effects research and standards development for noise, and for other acoustics research not feasible elsewhere in Canada. The chamber's free-field performance was quantified using measured deviations from the 1/R law for the variation of sound pressure with distance, R, from a point source in a free field. In measurements at 46 locations throughout the chamber, deviations were typically less than 1 dB for frequencies ranging from the design cutoff of 50 Hz to 20 kHz. The largest deviation was 1.9 dB. Impulse response analysis was also used to examine sound reflections. Background noise was found to be less than the design criteria used, which ranged from 22 dB at 50 Hz to 4 dB at and above 1600 Hz. Comparisons will be made to the few other chambers in the world which are of a similar size.