Prediction of Free-Field Noise Levels from Aircraft Flyover Measurements

摘要

Results from a flight experiment on a light propeller-driven aircraft were used to examine the ability to correct flyover noise spectra to free-field conditions. Flyover noise was measured when the aircraft was overhead. Average direct measurement spectra were obtained at a measuring station comprising a microphone placed at a height of 1.2 m over grassland and a microphone laid on a metal plate at ground level. Both measurement spectra were corrected for ground interference effects to yield the free-field noise characteristics. The theoretical model used for the prediction of the effects of ground reflection on aircraft noise recorded above a partly reflecting ground surface is presented. Comparison of corrected noise spectra from the two receiver positions demonstrates the potential to accurately deduce free-field noise levels from acoustic data measured by a single microphone arrangement.