Characterisation of structure borne sound sources in-situ

In theory it should be possible to characterise a vibration source's active and passive properties in an independent way which allows for structure borne sound to be predicted for a source in different installations. When put into practice however, the independent source characterisation approach often results in sur- prisingly poor predictions of source behaviour for the installed condition. The exact cause of the error is currently unknown but is often attributed to the practi- cal difficulties encountered when measuring source properties and hence numerical instabilities resulting from poor quality or unrepresentative data. Here we ad- dress the problem of obtaining independent descriptions of a source's active and passive properties using in-situ measurement approaches. In-situ measurements may be advantageous because the hypothetical quantities required for indepen- dent source characterisation are on the whole unmeasurable and hence elaborate measurements are often required to obtain an approximate source description. It will be shown that the independent blocked force, describing the activity of a vibration source under a blocked condition, can be measured in-situ and that the in-situ blocked force can be used to predict source behaviour in different environ- ments including a free condition. It will also be shown that the in-situ blocked force approach may allow for a transfer path analysis to be performed without dismantling the source-receiver assembly and thus allowing for a significant time saving. To address the characterisation of passive source properties two methods for the in-situ measurement of mobilities are described and investigated. Overall it is shown that active, and possibly passive, properties of vibration sources can be independently characterised whilst a source is installed and that there may be significant benefits in doing so. For example measurements may be faster or easier and the data obtained may be more representative.EThOS - Electronic Theses Online ServiceGBUnited Kingdo