Vibro-Acoustic Methods to Predict Chain Noise in Automotive Transfer Cases 2005-01-2344

The dynamic interactions between the chain links and sprocket during mesh are one of the predominant sources of noise in an automotive transfer case. This paper uses Vibro-Acoustic methods to predict chain-sprocket mesh noise using commercial numerical codes. Chain-sprocket excitations are simulated using a multi-body dynamics program at several speed steps. Subsequently, these dynamic forces are transformed from the time domain to frequency domain and used as an input to a finite element model of the transfer case. The surface velocities calculated due to these boundary conditions are used as an input to SYSNOISE, a vibro-acoustics program. The predicted sound pressure levels (SPL) and sound power levels (LW) from Sysnoise for each speed step are then compared with test data measured in a hemi-anechoic chamber. In addition, this paper also discusses the effects of “simplifying” the dynamic excitation forces due the chain-sprocket in order to reduce computation time. The results of these “simplifications” will then be presented, along with practical engineering guidelines, for predicting chain noise from a transfer case.