There is an increasing demand for quieter operation of motor-driven products from the perspective of improving comfort. In particular, noise generated by motor fans can sometimes cause problems due to the presence of pure sound components, such as blade and electromagnetic noise, at peak levels. In order to achieve quieter and lower-vibration operation, it is often necessary to first assess the performance of existing products by measuring noise and vibration. One method of measuring sound involves using beamforming techniques to detect sound sources. While this method allows sound sources about a product to be visualized, it does not reveal how sound propagates through space from the product. Understanding sound propagation behavior is expected to enable optimal placement of sound-absorbing structures.
Kawata et al. (Wed,) studied this question.