Moving Frame Acoustic Holography and its possible Applications in Machine Monitoring and Diagnostics

Abstract

Moving frame acoustic holography has been successfully applied to predict sound pressure distribution on the surface of interest to us. It has been motivated to enlarge the aperture size of the hologram. In the meantime, however, a great deal of application has been found in what is related to making sound image with regard to time as well as frequency. The method is, in fact, analogous to a copy machine. We make the image of sound, instead of duplicating light image, which has to do with a copy machine. The theory [Y.-H. Park and S.-H. Kim, J. Acoust. Soc. Am. 104, 3179–3189 (1998)] shows that we can travel an array of microphones over the surface of which we want to have a sound/noise image. The theory also permits one to recover the sound image from the data obtained by the array microphone fixed on the ground. The sound image is the spatial characteristics of sound that will be observed by the microphone system attached to the sources. This paper reviews possible areas of applications for a train or subway, or a quality control system in a factory.