Prediction of Airborne Sound Transmission into the Passenger Compartment 2015-01-2266
Several of the exterior noise sources existing around a vehicle can cause airborne noise issues at relatively low frequencies. SEA, traditionally used for airborne sound issues is not suitable for the frequency range of interest. Finite Element analysis has been used. Handling of the non-reflecting condition on the outer boundary of the exterior cavity is an issue. Recently, advances have been made in several commercially available codes, which made the analysis practical. Including the poro-elastic material model for foam-based carpets is also becoming practically possible.
The purpose of the current study is to investigate the practical applications of those new developments against test data, and to estimate the feasibility of using these procedures in the vehicle development projects. Measurements were carried out in a new semi-anechoic chamber at Volvo Cars. These measurements involved 3 body objects - a Body-in-Blue (BIB) sedan, a Complete Vehicle (CV) sedan and a CV wagon. The measured BIB configurations included also the ones with individual carpets. Several microphones were used outside of the bodies in order to monitor the exterior sound field. A sound source was placed initially at the exhaust pipe position. Later, more positions for the sound source were used and measurements were extended to higher frequencies.
The accuracy of predictions obtained with different modeling approaches is discussed. Practical aspects of running such CAE analyses are highlighted. The feasibility of application of CAE analysis in vehicle development projects for exterior source issues is assessed.