An Experimental Study of Mechanism of Body Panel Vibration in Booming Noise Reduction of Passenger Vehicles

In a typical passenger vehicle, there can be different types of noises generated which are broadly categorized as Interior Noise and Exterior Noise. The interior noise sources can be further classified into noises which can be Structure Borne or Air Borne. One of the major sources of both structure borne and airborne noise generation is the powertrain of the vehicle. The structure-borne noise and vibrations generated from the powertrain is usually transferred to the vehicle body through its attachment points to the body and the powertrain driveline. These induced body vibrations can sometimes cause the acoustic cavity of the passenger cabin to go into resonance which results in an annoying and disturbing noise for the passengers, called Booming Noise. Very often, one or more than one vehicle body panels show a dominant contribution in inducing this acoustic cavity resonance. In this research, the backdoor of the selected passenger cars were identified to be one of the primary contributors in causing the booming noise phenomena. The objective of this research was to study the mechanism of the contribution of backdoor towards booming noise in these hatchback style passenger vehicles. The study was carried out on three differently styled hatchbacks namely Model A, Model B, and Model C. The study of the mechanism behind this contribution was carried out in three phases. The first phase included the response measurements of the individual grid points created on the backdoor which were excited using a low frequency sound source. In the second phase, a computer model of the grid structure of the backdoor was created and the response measurements obtained were superimposed on the geometry model to identify the modal parameters of the backdoor. The identification of the modal parameters helped in understanding the modal behavior of the backdoor which is causing the acoustic resonance of the cabin cavity thus creating the booming noise phenomena. In the third phase, in cabin acoustic measurements were carried out during vehicle acceleration tests and the results were correlated with the modal parameter data. This helped in identification of the dominant modal frequencies to be targeted for further design improvements during concept & vehicle design stage.