A BE Model for the Analysis of the Effects of Seats in the Passenger Compartment Acoustic Behaviour 1999-01-1790
The aim of this work is to validate a BE numerical methodology to calculate how the acoustic properties of seats can affect the acoustic behaviour of the passenger compartment of a vehicle.
An analytical model, based on the Delany and Bazley approach, was implemented in order to simulate the acoustic impedance of the foam-fabric system. This model has been validated with absorption coefficient measurements on a certain number of foam-fabric combinations.
The calculated impedance was used as input for a BEM analysis of the interior cavity of a trimmed vehicle. The measured impedance of trimming components as floor carpet, door panels and parcel shelf were included into the cavity model. The acoustic field due to a known source with and without seats was calculated, in the frequency range 20-400 Hz: the calculated FRFs are in good agreement with the measured ones.
The analysis has demonstrated that the presence of seats does not improve the absorption of the passenger compartment in the frequency range investigated: the seats modify the peak position in the FRFs but do not lower their level.
Reverberation time measurements made in the passenger cavity with and without seats have, on the contrary, put into evidence an important seat contribution in lowering the interior noise above 1000 Hz: the reverberation time in this frequency region has been reduced by about 50% by the presence of seats.