An Analysis of Aircraft Flyover Noise
BOLT BERANEK AND NEWMAN INC CANOGA PARK CA
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A detailed analysis of a set of Boeing 727 aircraft flyover noise measurements is presented. The flyover data were acquired over a wide range of sideline distances and angles of aircraft elevation with respect to the measurement position. Relationships are derived for excess attenuation due to ground effect and reflection interference as a function of both frequency and angle of aircraft elevation. Angle of elevation is found to be the principal normalizing factor for excess attenuation in the frequency range 50 - 1600 Hz over measurement distances of 800 - 9000 feet. Ground effect, separable from ground reflection interference phenomena in this analysis, was found to be a maximun in the frequency range 125 - 400 Hz and as high as 17 dB at an aircraft elevation angle of 4 deg. Spectral distortion due to reflection interference is found to be important at high angles of elevation but diminishes rapidly at aircraft elevation angles of less than 20 deg. Recommendations are presented on the use of the results of this analysis to guide the development of improved flyover noise prediction techniques.