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With the stringent legislative requirements for noise in automobiles, gensets etc., the concern for properly designed silencers for specific applications is increasing. Optimized design of silencer requires an integrated study of acoustical and engine performance viz. Insertion loss and backpressure. However, the insertion loss itself depends upon engine characteristics geometry indicated by the transmission loss, flow induced noise, type of silencer - reactive, absorptive, hybrid, etc. Most of the work till date covers the acoustical and engine performance in isolation rather than in an integrated fashion due to the multidisciplinary nature of the problem. The objective of this study is to develop an integrated methodology to predict the performance of the silencer at the design stage resulting in an optimized time and cost effective design. In the present study, the acoustical and engine performance of silencer was predicted using FEM/BEM and CFD techniques.

Modern vehicles are designed for quiet interior with lower engine and exhaust noise levels. Under such circumstances, gear whine and rattle become one of the significant contributors towards in-cab noise, besides wind and road noise. Present paper deals with dynamic analysis, simulation and validation of the transmission system model for observed gear whine inside the cabin of a passenger car during its running condition. The exercise included development of an accurate numerical model to enable prediction of noise transmission from automatic gearbox to cabin structure. Experimental Modal Testing (EMT) of automatic transmission and suspension components, Multibody simulation of automatic transmission and Finite Element Analysis (FEA) of components and subassemblies followed by component and system level response correlations were carried out. Detailed methodology adopted for the exercise is discussed in the paper.