TRANSMISSION OF SOUND THROUGH A CYLINDRICAL SHELL AND A LIGHT AIRCRAFT FUSELAGE
Abstract
A light aircraft fuselage was modeled as a half-scale cylindrical shell to study the sound transmission through the structure. An analytical model based on Statistical Energy Analysis (SEA) was developed for predicting the sound transmission loss of the cylindrical shell in the frequency range above 500 Hz. The parameters involved in the SEA model such as modal densities and radiation efficiencies were obtained from the wavenumber diagram using a numerical technique. In the low frequency range, a band-limited power flow model was used to predict the noise reduction of the cylinder. In this low frequency model, the resonant transmission was calculated for each cavity mode and the non-resonant transmission was computed by using the mass-law. The transmission losses of the cylindrical shell and a full scale aircraft fuselage were experimentally evaluated by measuring the incident and transmitted intensities. The transmitted intensity was measured by using the two-microphone acoustic intensity technique with the aid of an FFT analyzer. This new method of evaluation of transmission loss was found to give more accurate results than the conventional method. On the basis of the theoretical predictions and the experimental results, the dominant noise paths on the aircraft fuselage have been found and possible ways of reducing the transmission of noise into the fuselage have been suggested.
Degree
Ph.D.
Subject Area
Mechanical engineering
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