A means to see noise sources

Abstract

There are many candidates to visualize noise/sound sources. For example, acoustic holography is one of them. However, to get acoustic holography, we need many microphones and associated data acquisition and processing unit. Especially, when noise is impulsive, the holography system requires two-dimensional microphone array. Depending on the type of noise sources, we have to select the best means that can provide us what we want to have, which can be noise sources' locations or entire sound distribution in space. This paper addresses various methods that can predict where noise sources are, or how noise is distributed in space. This includes beam forming methods to determine steady or impulsive noise sources, conventional acoustic holography, time domain acoustic holography and moving frame method that can show moving noise sources. We compare these methods and show a guide line that can lead us to select the best means to see noise sources. Various industrial examples are introduced. Time domain acoustic holography of plasma display panel that shows very interesting vibration pattern, beam forming method that depicts short and small noise generated by thermal expansion of TV set, and moving frame method that shows tire noise are some of the examples.