Nonlinear Propagation Distortion of Jet Noise.
TEXAS UNIV AT AUSTIN APPLIED RESEARCH LABS
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A previous theoretical and experimental study of intense broadband noise in a tube showed that propagation distortion is significant for plane waves at sound pressure levels encountered in jet noise fields. A computer program was later modified to account for spherical spreading. In the study reported here, measured noise near actual jets was used as the input for the program. The distortion that is expected to occur during subsequent propagation was computed. Computations were made for noise from a model supersonic jet and from a T38 aircraft. In both cases the computed waveforms exhibit shocks and other evidence of nonlinear effects at moderate distances. However, the model does not include atmospheric attenuation and meteorological effects, ground reflection and absorption, and effects due to the complicated nature of the jet source itself. An outdoor propagation experiment using noise from a conventional sound source is planned for the future.
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