HIGH FREQUENCY NOISE SOURCE IDENTIFICATION OF MACHINE STRUCTURE : APPLICATIONS OF CNVERTED NEARFIELD ACOUSTIC HOLOGRAPHY

There are several types of sound localization methods of which the holographic methods are mainly used for middle frequency sound localization because of its high resolution. While, these methods have a demerit taking long time to measure sound field when applied for the high frequency sound localization. This problem is caused by the sampling law in the spatial domain. We have developed new holographic method converted Nearfield Acoustic Holography method which can quickly measure the high frequency noise. In this paper, as examples, the experiments for a speaker and gears with speed control motor are explained. As a result, it is found that the reconstructed images themselves are not sharp, but nearly indicate the noise source location