Estimation of Plate Vibration and Its Far Field Sound by Means of Near Field Sound Measurement

As one approach to noise problem of machinery, advantages of near field sound measurement are discussed for a resonating rectangular steel plate. A proposed technique after Acoustic Intensity Method was applied to measure the distributions of both intensity and particle velocity over a plane placed close to a sound source. Particle velocity in the normal direction of plate proved to be reliable for estimating the vibration of the plate surface. And far field sound pressure is calculated accurately from it. In addition, for the ease of calculating far field sound pressure form a known mode of vibration, a simple approximation by which the sound source can be replaced by the least number of point sources, is also proposed.