STRUCTURE-BORNE SOUND SOURCES IN BUILDINGS: TOWARDS METHODS, STANDARDS AND DATA BASES

The prediction of structure-borne sound pressure levels (i.e. radiated sound due to vibration transmission between machines and supporting/connected structures) is a more complicated process than for airborne sources. However, practitioners require methods and data for the former which are as straightforward as for the latter. The source-path-receiver model for airborne sound must be modified to a source-transmission-path-receiver model for structure-borne sound. To obtain the transmission, three quantities are required in some form: source activity (either the free velocity or the blocked force of the machine), source mobility and the receiver mobility of the connected structure. The three quantities can be expressed approximately as frequency band-averaged values, e.g. in one-third octave bands, and also expressed as equivalent single values. The source free velocity and source mobility can be obtained in the laboratory by using the reception plate method. Alternatively, the source and receiver mobilities can be calculated, using simple plate and beam theory. A form of data base is proposed, to allow consultants and design engineers in building acoustics to predict structure-borne sound power into the connected building element and thence the radiated pressure.