Investigating the sound pressure level inside the passenger cabin of an automobile using a vibro-acoustic model

Abstract

The interior noise inside the passenger cabin of automobiles can be classified as structure borne or airborne. In this study, we investigate the structure-borne noise which is mainly caused by the vibrating panels enclosing the vehicle. Excitation coming from the engine causes the panels to vibrate at their resonance frequencies and these vibrating panels cause a change in the sound pressure level (SPL) inside the passenger cabin and undesirable booming noise. In order to improve the passenger comfort inside the vehicle, it is critical to understand the dynamics of the vehicle and more importantly how it couples with the air inside the cabin. For that reason, finite element (FE) model of the passenger cabin was created and vibroacoustic analysis was performed to predict the interior noise inside the passenger cabin of a commercial automobile using two different methods, coupled and uncoupled analysis. Coupled analysis considers the mutual interaction between the fluid and the structure whereas the uncoupled analysis considers only one way interaction (structure to fluid for the case study presented here). Also the most significant disturbance source is identified by comparing the results of the sound pressure level under the effect of force disturbances applied at different directions and engine mount locations.