Finite Element Modeling Method of Vibro-Acoustic Systems for Mid-Frequency Simulation

Current vehicle acoustic performance prediction methods, CAE (computer aided engineering) or physical testing, have some difficulty predicting interior sound in the mid-frequency range (300 to 1000 Hz). It is in this frequency range where the overall acoustic performance becomes sensitive to not only the contributions of structure-borne sources, which can be studied using traditional finite element analysis (FEA) methods, but also the contribution of airborne noise sources which increase proportional to frequency. It is in this higher frequency range (>1000 Hz) that physical testing and statistical CAE methods are traditionally used for performance studies. This paper will discuss a study that was undertaken to test the capability of a finite element modeling method that can accurately simulate air-borne noise phenomena in the mid-frequency range. This modeling method was used to create a model of an enclosed simple box-shaped vibro-acoustic system fit with various acoustic trim parts (carpet and under body covers). Using a single external sound source as excitation, the interior sound pressure levels of the enclosure were simulated and compared to test data from a physical representation of the model. In the frequency range of 150 to 1000 Hz, the FEA model was proven capable of predicting, to a high level of correlation, the exterior and interior sound pressure levels of the enclosure and the noise reduction effects from the several trim components studied. This paper will also discuss how this modeling method could be used to perform sound reduction mechanism studies focused on how individual layers of a trim part’s composition can contribute to its overall sound reduction effectiveness creating a potential avenue for performance optimization.