Abstract
One of the authors has developed a technique to measure the transient vibration on unstable structure, for example, paper, film and so on, by using sound pressure measurement at near field. In this papeらthe theory of point sound source is studied to be constructed in order to verify the technique. The technique is discussed by using the wood speaker which vibration responses can be directly measured by accelerometcrs on the speaker unit and which sound pressure is measured by microphones near the speaker unit. And experiment that used two dimension of structure to develop the theory of point sound source was tried. As a result, it was understood that the theory consisted at time when the position of the microphone was 5mm.
