Acoustical Nonlinearities in Aircraft Flyover Data

Numerous analyses techniques have been proposed as means of characterizing acoustical nonlinearities in high-thrust engine noise. These include probability distributions for the pressure and the time derivative of the pressure (i.e., the gradient), the skewness and kurtosis coefficients of the pressure and its time derivative, and Howell-Morfey nonlinear indicators. In this paper, a number of these analyses techniques are applied to acoustic data recorded during a series of military jet flyovers. The analysis examines these different measures as a function of microphone height above the ground. This analysis provides strong indications that microphone should be mounted well above the ground to properly measure nonlinearities in high-thrust engine noise.

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