Quantifying Sonic Boom Metric Variability

Open Access
Author:
Palmer, Joshua David
Graduate Program:
Acoustics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
October 26, 2017
Committee Members:
  • Victor Ward Sparrow, Thesis Advisor
Keywords:
  • Sonic Boom
  • Acoustics
  • Sonic boom metrics
Abstract:
Various sonic boom noise metrics have been calculated for a number of sonic booms, N-wave signatures. The newly computed metrics dataset utilized high-quality recordings from the Superboom Caustic Analysis and Measurement Program (SCAMP) and Farfield Investigation of No-Boom Thresholds (FaINT) experiments conducted by NASA. With these signature datasets comprised of microphone measurements by long linear arrays, one can assess the waveform variability due in part 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. A preliminary metric currently under development by NASA, the Indoor Sonic Boom Annoyance Predictor (ISBAP), was also briefly analyzed. 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 and 1.2 dB to 6.1 dB for FaINT 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.