Jet aircraft noise at high subsonic flight Mach numbers

Acoustic overfly measurements are carried out and analyzed to identify the sound sources of the noise development by means of their spectral radiation properties. The extension of existing prediction schemes for the radiation mixing and the broadband shock noise is discussed on the basis of experimental results. Measure and calculation results were compared and a good agreement was found for the time profiles of noise levels, the frequency spectra, and the total sound pressure level as a function of emission angle. The prediction schema could be used to demonstrate the influence of operational parameters and quantify the noise production. It is shown that a decrease in flight Mach number and an increase of flight height cause an important noise reduction.