The range of applications of sound intensity measurement is rapidly increasing as the intensity measuring technique is applied by an increasing number of users. However, difficulties will always arise if the field is too reverberant. The electronic equipment cannot handle a small energy flow in a large reverberant field. The practical limits for today's best equipment is a maximum standing wave ratio (SWR) of 24dB. Therefore, in reverberant rooms it is necessary to use absorbing material for introducing some damping to keep the SWR at a reasonable level. The same limitations apply for measuring energy flow in mechanical structures. In most cases it is necessary to introduce damping either with discrete vibration absorbers or by painting the structures with a vibration absorbing material so that the SWR will be below 24 dB. This paper also describes a practical application of vibration analysis for production control of gear boxes, motors, and other complicated mechanical structures. By using energy flow techniques together with vibration absorbers many problems can be solved.
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