Subjective loudness of sonic-boom: N-wave and minimized (low-boom) signatures

A loudspeaker-driven simulation booth with extended rise-time capability (down to 0.22 ms) was used for subjective loudness tests of sonic booms. Test series 1 compared N-waves over a range of 0.22 to 10 ms rise time, 100 to 250 ms duration and 0.5 to 2.0 psf (24 to 96 N/sqm) peak overpressure. Tradeoff between rise time and overpressure was measured for equal loudness, as well as 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 to 200 ms but at 250 ms noticeably enhanced the loudness. Test series 2 compared certain flat-top sonic boom signatures with a reference N-wave (0.5 psf, 1 ms rise time, 150 ms duration). For equal subjective loudness, flat top vs. N-wave, the peak amplitude of the flat top signature was substantially higher than that of the N-wave; thus for equal amplitude the flat-top signature was quieter.