Measured N-wave sonic boom events and sensitivity in sonic boom metrics

Various sonic boom noise metrics have been calculated for a number of sonic boom, N-wave signatures. The newly computed metrics dataset utilized high-quality recordings from the Superboom Caustic Analysis and Measurement Program (SCAMP) experiment conducted by NASA. With this signature dataset comprised of microphone measurements by long linear arrays, one can assess the waveform variability due to atmospheric turbulence influences across the arrays. Preferred boom events from these NASA datasets were then chosen after review of the flight conditions, flight objectives and actual waveforms generated in order to study only the non-focused, N-wave sonic boom signatures. The sonic boom noise metrics calculated for the preferred boom events include Stevens Mark VII Perceived Level (PLdB), un-weighted Sound Exposure Level (SELz) as well as Sound Exposure Level with A, B, C, D, and E weightings applied to the waveforms. The results show, for example, that the A-weighted sound exposure levels and Steven’s Mark VII Perceived Levels had standard deviations in the range of 1.4 dB to 6.1 dB for the SCAMP measurements. Such sensitivity results should be helpful in assessing the applicability of sonic boom metrics for use in future en-route certification standards for civilian supersonic aircraft.