Comparison of the use of two methods for characterizing structure-borne sound sources

In the analysis of structure-borne sound generation the characterisation of sources is of importance. In this paper the application of two methods are presented and compared: a mobility matrix approach and a pseudo-forces approach. The methods are applied to a laboratory test rig. Both methods are used in order to estimate a sound pressure level near the test rig, based on the source characterisation and corresponding transfer functions. The sound pressure estimate using the mobility matrix approach was accurate within about a 10 dB interval and the estimate using the pseudo-forces was accurate within about a 2-4 dB interval. Although the result for the pseudo-forces is much better, it appeared that for this case the transportability of the pseudo-forces to a different mounting case was poor. It is concluded that explicitly dealing with the source/receiver coupling is cumbersome in case of extreme changes in boundary conditions. It is recommended to use implicitly measured coupling characteristics if possible.