Obtaining internal and coupling loss factors by a transient test method

Abstract

Statistical energy analysis (SEA) is taking an increasing role in determining energy flow and predicting noise reduction of machine structures. In order to set up the SEA model it is necessary to obtain the internal and coupling loss factors of each substructure either from theory or from measurement. The conventional measurement technique, in which steady-state input power is supplied by a shaker to each subsystem in turn, is very time consuming. Moreover, it is not always possible to attach the shaker in the best position due to space limitations. This paper describes a transient method of loss factor measurement, using an instrumented hammer, which overcomes the above-mentioned difficulties. The technique uses the point and transfer inertance data for the structure to calculate input powers and subsystem energies. Results obtained by this method are compared with those obtained conventionally and good agreeement is demonstrated.