On vibration absorbers for vibration and noise attenuation for the fuselage and cabin of selected tonal engine disturbance, based on ground measurements

Abstract

Engine noise is of substantial impact on the passenger's comfort of modern airplanes. Besides the jet noise, certain selected tonal engine frequencies can be clearly observed as acoustic noise in the cabin. Based on ground measure-ments on a Dassault Falcon 2000LX MSN 006 airplane, three of these tonal frequencies have been identified and strategies have been developed to attenuate these frequencies with active and passive solutions subsequently. In this paper, the principal properties of vibration absorbers, mounted at one pylon, have been investigated, based on the spectral disturbances and frequency response functions, obtained from the ground test measurements. Using a vibration absorber at the pylon between the engine and the fuselage is suggested by the idea, to at least attenuate the structure borne noise of this path. The main focus of the presented study reveals the principle possibilities and restrictions of using vibration absorbers to vibration reduction on certain parts of the fuselage and on sound power reduction in certain cabin areas. Due to the fact, that only one position for an absorber was available from the underlying measurement data, numerical results are only available for one absorber at a fixed location. As part of the conclusion of the paper, using multiple absorbers would be mandatory to gain sufficient global attenuation, but the principles can be demonstrated fairly well with the chosen set up.