SUBJECTIVE LOUDNESS OF N-WAVE SONIC-BOOMS

A loudspeaker-driven simulation booth with extended rise-time capability (down to 0. 22 ms) has been used for subjective loudness tests of N-wave sonic booms. The test series compared signatures over a range of 0. 22-10 ms in rise time, 100-250 ms in duration and 0. 5-2. 5 psf (24-120 Pa) in peak overpressure. In one sequence, the tradeoff between rise time and overpressure was measured for equal loudness; in another, the tradeoff between duration and overpressure. For equal loudness 10-ms rise time required 8-dB higher overpressure than for 1-ms rise time. Duration had little effect in the range 100-200 ms, but at 250 ms noticeably enhanced the loudness. These results confirm those measured by Shepherd and Sutherland made at 1-ms rise time and above (except for the anomalous enhancement at 250-ms duration), and extend the measurements down to 0. 22 ms. There is also good agreement with theoretical predictions (Johnson-Robinson, Zepler-Harel methods) except for the 10-ms rise time and 250-ms duration cases.