Analysis of Transient Sounds by Sound intensity Techniques.

Abstract

Sound intensity measurement is very useful for analysis of sound fields. A time-averaged intensity is usually applied to process time-invariant signals. In order to analyze a transient sound, the conventional sound intensity must be modified or other methods must be applied. To evaluate this kind of sound, a new method called 'envelope intensity' has been proposed. In this paper, we propose another new method called 'momentary intensity (MI)'. MI is obtained from an integration of the instantaneous sound intensity spectrum which is calculated by a cross-Wigner distribution of both sound pressure and velocity, with respect to frequency. As interference terms in a Wigner distribution are cancelled by the integration, MI can be applied for the analysis of nonstationary signals. Transient sounds are analyzed by envelope intensity and MI in this study. In a comparison of the results obtained from the two methods, MI is proved to be superior in resolution to envelope intensity, and to be able to extract much new information which cannot be obtained through other methods.