Probability distributions of sonic boom noise metrics in isotropic turbulent fields

Abstract

Sonic boom waveform distortion caused by isotropic turbulence is examined with numerical simulations of acoustic propagation through randomly generated 3D turbulent fields. A recently developed planar, one way acoustic propagation code is used in this study to simulate the propagation of sonic boom waveforms. Computations of the signal account for diffraction, signal scattering by turbulence, nonlinear distortion, and absorption. Two types of waveforms are considered, one type is an N-wave and the other is a shaped boom. The intensity of the turbulent field is systematically varied for each set of simulations. For each condition, simulations through hundreds of randomly generated fields are conducted to obtain the statistical means and variances of PL, ISBAP, and select weighted SEL metrics. The computational results provide insight on the dependence of the probability distribution of each metric on the turbulence intensity and propagation distance. The data is further examined to compute probability density functions for each metric as a function of the turbulence intensity at different propagation distances. These functions provide insight on the effects of turbulence on the loudness levels of sonic booms. Future work and applicability of the results to atmospheric boundary layer turbulence is considered. [NASA Fellowship Activity Grant No. 80NSSC19K1685.]