Characterisation of structure borne sound sources in-situ

Elliott, A S

Abstract

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.

Citation

Elliott, A. S. Characterisation of structure borne sound sources in-situ. (Thesis). University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: May 1, 2009