Laboratory Simulation of Sonic Booms

Abstract

Sonic-boom signatures, including measurements from existing aircraft and predicted waveforms for the supersonic transport, have been reproduced in a laboratory facility. The facility is used to obtain judgments from human subjects on various subjective parameters of sonic booms. This simulation was accomplished using an array of loudspeakers coupled to a 70-ft3 a sealed chamber to produce the appropriate pressure field inside at the subject position. An electronic analog of the sonic-boom pressure wave, recorded on magnetic tape, is delivered to shaping networks and dc amplifiers, which in turn drive the loudspeakers. Signal-conditioning in the system includes the response compensation necessary to achieve rise times (associated with the abrupt pressure gradients of the bow and tail waves) of the order of 1–2 msec. The techniques used to generate the electronic analogs of the sonic-boom pressure waves make it possible to reproduce any waveform for use with the simulator system. Judgment tests comparing the perceived loudness of sonic booms have been carried out for identical signatures, different nearfield waveforms, and signatures differing only in duration.