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The subjective quality of sounds is a topic of increasing importance in the automotive industry. The first consideration is to describe the perceptual characteristics of this quality by means of jury tests or appropriate metrics. Once a NVH problem is determined in terms of an appropriate Sound Quality description, an in-depth analysis of the underlying physical phenomena must be made and engineering solutions newel to be proposed and validated This involves: • the detailed analysis of the signal structure in the time, frequency and order domain and identifying the signal Components Critical to the relevant sound quality dimension • the Correlation of the critical signal components to specific sources noise or vibration transmission paths and vibro-acoustic system characteristics. Ultimately this should lead to the prediction of the effect of feasible modifications in sound quality terms through the use of engineering models.

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.

This paper discusses a road noise analysis application on a passenger car. It involves a study of the interior noise in the car, which is explained in function of the energy transfer paths from the suspension into the car body. For this, multiple reference transfer path analysis is used. A link is made between specific characteristics of this energy transfer and the operational analysis of the measurements on the suspension during road tests, as well as the acoustical modes of the cavity. The operational data are correlated with modal analysis results on the suspension, explaining certain problems occurring during running condition.