Noise Characteristics of Jet Aircraft at High Speed/Low Altitude Flight

Abstract

Flyover noise measurements are evaluated for four different military jet aircraft types flying at low altitudes. Flight Mach numbers ranged from 0.5 to 0.9. The analysis shows that noise immission is likely caused by jet mixing and broadband shock associated noise. Based on the experimental results existing noise prediction schemes are extended towards higher subsonic flight Mach numbers. The novel prediction schemes describe the observed acoustic signatures quite accurately. This holds for the overall sound pressure level in dependence of the emission angle and for 1/3-octave spectra. The prediction schemes are used to demonstrate and quantify the noise reduction potential achievable by varying flight Mach numbers and flight altitude.