Nonlinear Propagation of Aircraft Noise in the Atmosphere

Abstract

Carefully controlled tests of aircraft noise propagation have shown instances of anomalously low attenuation (deficiencies in excess of 10 dB over 500 m) for frequencies in the range 5-10 kHz. These results have been explained with the aid of a statistical theory of finite-amplitude noise propagation. Detailed analysis of recordings from one test has provided a direct check on the nonlinear theory. Results from several different tests have been incorporated in a statistical model, which allows the nonlinear distortion of aircraft noise spectra to be estimated as a function of distance, level, spectrum shape, and atmospheric conditions. Preliminary results show encouraging agreement with the anomalous data.