On the Analysis of the Wave Motion in a Coupler for the Pressure Calibratnion of Laboratory Standard Microphones

Abstract

A theoretical study is made of the corrections for coupler calibration of laboratory standard microphones. In the analysis, the effect of wave motion in a coupler is discussed, taking into consideration the interaction between the microphone diaphragm and the medium. A new method of solving the wave equations, called the infinite-matrix method, is presented in this paper. A coupler is divided into several right circular cylinders and two diaphragms. Each part can easily be solved in general form as an expansion into orthogonal functions. After arranging these solutions in the form of matrix equations with unknown variables, we obtain a system of simultaneous matrix equations by connecting the solutions together. Exact solutions of the wave motion correcting as well as the transmission characteristics for both type 20 cc and 3cc couplers are presented. It is also confirmed that numerical results for the case of the transmission characteristics of the 20cc coupler are rapidly convergent.