Real time separation of time domain progressive and retrogressive sound waves by a correlation method.

Abstract

This paper describes a method for separating each of progressive (direct) and retrogressive (reflected) sound waves in real time which are traveling between the source and the reflector and are overlapped mutually. In this method, the sound wave is expressed and measured in the form of a correlation function obtained from the source and receiver signals in the case of scanning the time delay (variable) and fixing the receiving position (parameter). In order to realize the real time separation, three microphones closely set at the receiving position are used. From them, time delay differential and space differential values are derived. Then, by addition and subtraction of these two differential values, each of progressive and retrogressive sound waves can be obtained separately. Some experiments based on the theory in the case of normal incidence are carried out. Then, considering about the measured sound waves concerning the attenuation by distance and the traveling time, it is shown that the theory and the procedure of separating are valid. But, it is not yet about the case of oblique incidence.