Body Induced Boom Noise Control by Hybrid Integrated Approach for a Passenger Car

Vehicle incab booming perception, a low frequency response of the structure to the various excitations presents a challenging task for the NVH engineers. The excitation to the structure causing boom can either be power train induced, depending upon the number of cylinders or the road inputs, while transfer paths for the excitation is mainly through the power train mounts or the suspension attachments to the body. The body responds to those input excitations by virtue of the dynamic behavior mainly governed by its modal characteristics.

This paper explains in detail an integrated approach, of both experimental and numerical techniques devised to investigate the mechanism for boom noise generation. It is therefore important, to understand the modal behavior of the structure. The modal characteristics from the structural modal test enable to locate the natural frequencies and mode shapes of the body, which are likely to get excited due to the operating excitations. The critical transfer paths for the excitation through the structure have been identified with the help of transfer path analysis, while running mode analysis indicate the dynamic behavior of the structure due to the excitation. Similarly, the acoustic modal analysis describes the fundamental acoustic modal characteristics of the cabin cavity. The introduction of the experimental running mode inputs of the structure to the acoustic finite element model makes the hybrid analysis possible. The panel contribution analysis focuses on the components that have the significant contribution in the booming noise for in-phase as well as out of phase panels. The modifications revealed from the systematic study by hybrid approach, has led to substantial reduction in the booming noise both objectively and subjectively. This paper also describes the improvements suggested to reduce the boom noise.