Quantification of sonic-boom distortion resulting from propagation through the Earth’s turbulent boundary layer.

Abstract

Using digitized sonic-boom waveforms from aircraft overflights recorded by the Air Force (Edwards AFB, 1987), a method has been developed to quantify the amount of distortion present in a sonic boom, using a classic N-wave model for comparison. A statistical relation between waveform distortion and the amount of turbulence a sonic boom encounters during propagation is sought. Using the premise that energy conservation applies approximately for a sonic boom both before and after passage through the Earth’s turbulent boundary layer, a model N wave is constructed from the distorted boom signature received at the ground. The mean-squared error between the actual and constructed signatures serves as a measure of waveform distortion and is seen to correlate with the distance the wave travels through the turbulence. [Work supported by NASA-LRC.]