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The correct quantification of airborne sources and their transfer to the vehicle interior noise enables vehicle manufacturers to set system targets and to assess interior noise effects of new or modified systems. Measurements on complete vehicles and on test-beds for body, engine, exhaust, tire, HVAC etc. can then be used to estimate interior noise contributions and choose an optimal level of solutions. This study addresses exhaust tailpipe airborne noise emission in a highly controlled situation; indoors and with an exhaust simulator. Two methods of characterization are compared. One method uses the sound pressure very close to the active source as a source strength combined with pressure transmissibility to estimate the interior noise contributions. The other method uses an inverse estimate of the source volume acceleration and the pressure over volume acceleration transfer for the same purpose. The methods of airborne contribution analysis are briefly described.

Vibro-acoustical optimization of vehicles is a complex task, due to the many interactions that exist between subcomponents and car body in a broad acoustical frequency range. The goal of this paper is to present a view on the different experimental methodologies for vibro-acoustical analysis, that approach the vehicle as a source, transfer and receiver system. This approach focuses on the use of transfer path and source identification techniques, both for structure-borne and air-borne contribution analysis, and on the use of modeling techniques as there are vibro-acoustical modal analysis, FRF based substructuring and experimental statistical energy analysis techniques. It is explained what the main focus is of each of the techniques, where they can be used in the vibro-acoustical optimization process and in which frequency ranges they are useful.