An anechoic chamber and point source design for audiological measurement

A point source in a 6-ft cubed anechoic space was designed to provide predictable audio sound fields at 1 m without near-field effects. The chamber was acoustically isolated to permit measurement down to 25 dB SPL in an 812 × 9 × 11foot o.d. enclosure. A control microphone 20 cm from the source maintained a constant SPL at 1 m over the entire frequency range. The presence of a full size human manikin did not affect the sound field at the control microphone. SPL followed inverse square law (± 1 dB) from 10 cm to 1 m from the source over a 200 Hz to l0 kHz frequency range. Eight loudspeakers, mounted behind the upper edge wedges could develop 70 dB SPL quasi-diffuse noise at the working location.