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Modern variable‐speed drive systems using frequency converters generate additional audible noise as a result of the voltages that are no longer sinusoidal. Using suitable measures, the purpose of this paper is to find an optimum for minimum noise radiation in the complete drive system.

The main areas to concentrate on to achieve an optimum are the source of excitation itself – the frequency converter, as well as the actual source of the noise, the motor. Optimization measures are drawn‐up using soundscaping with subsequent modal analysis of the actual state. The effectiveness of any changes made can be estimated using simulation techniques. This approach is confirmed by subsequently implementing the selected measures and verifying them by performing the appropriate measurements.

The paper takes care of the increasingly important field of converter‐fed drive systems and their special acoustical challenge. It shows a practical way to reduce audible noise combining measurements and simulations.

Combining the measurement of the acoustic camera with the simulation of modal shapes is a fast way for optimizing an inverter‐fed drive system.

The oil film thickness provides a key performance indicator of a ball bearing lubrication condition. This paper aims to propose an approach to calculate and measure the oil film thickness of the bearing.

On a specially designed test rig, measurement of the capacitance is used to monitor the oil film thickness of ball bearing. A corrected film thickness formula taking account of the influences of non-Newtonian shear thinning and thermal is introduced to predict the oil film thickness of ball bearing. And then the film thickness distribution and the corresponding capacitances are calculated.

Measurement and calculation of oil film thickness in a ball bearing are carried out under various rotating speeds and external loads. By comparing the calculated capacitances with measured results, it can be concluded that the calculated results obtained by the amended film thickness formula are much closer to the test findings than the classical computed values according to Hamrock–Dowson.

A new corrected film thickness formula is introduced in predicting oil film thickness of ball bearing and verified by the series of experiments according to capacitance method.