On the characteristic power of structure-borne sound sources

The paper deals with methods of independently characterizing sources of structure-borne sound. The concept of mirror power is introduced, which is the power delivered by a vibration source when connected to a passive receiver structure that is a mirror image of itself. A second quantity, the characteristic power is defined to be the dot product of the blocked force and free velocity vectors and this is shown to be four times the mirror power. In addition, expressions are given for the maximum available power from a source. These three concepts each provide, in a single value, an independent characterization of a structure-borne sound source. They are valid for multiple point and component contact as well as for contact over extended areas. The characteristic power (CP) is shown to be the most practical of the three, and examples of the CP of several real machine sources are given. It is shown that the emission from a source when installed is usually a fraction of the CP. This factor depends on the ratio of the source and receiver mobilities, and the trends in its behaviour can be predicted simply from the ratio of typical point mobilities of the source and receiver. CP thus provides an equivalent single point formulation for characterizing structure-borne sound sources. (C) 2001 Academic Press.