Coincidence effect with sound waves in a finite plate

Abstract This paper discusses the occurrence of coincidence effect with sound waves in the light of the original discussion of the phenomenon and of some recent work. The paper satisfactorily explains the occurrence of coincidence effect in (i) a finite plate backed by a cavity, and (ii) a finite plate having no backing cavity. The paper discusses the theoretical conclusion derived from the finite plate theory of coincidence supported by experimental evidence which shows that sound waves incident obliquely on a plate backed by a cavity cause coincidence effect at a fixed frequency, independent of the angle of incidence. The paper makes a brief review of the other works related to the occurrence of the coincidence effect in infinite and finite plates. It is also shown that it is theoretically impossible to visualize coincidence transmission in a freely suspended or supported finite plate by the condition of matching between flexural and acoustic waves unless the plate is backed by a cavity.