Acoustic Directional Couplers

Abstract

Although it is known in the measurements of electromagnetic wave that the directional coupler is a useful means in separating an incident wave from a reflected wave at a fixes position, the utilization of the directional coupler in this form has not yet being introduced in acoustics. Authors are suggesting the application of the acoustic coupler in the two new phases in acoustics, namely; in measuring of amplitude reflection coefficients (complex quantity) and in directional microphones. The purpose of this paper is to explain their advantages and the prospection extensive usage in the future. The directional coupler when applied for measuring amplitude reflection coefficients, the system as a whole is a stationary equipment having no movable components, so it would be free from errors causable from mechanical looseness, thus enabling a practical accuracy at higher frequencies together with the virture of shortening the time considerably for its operation. A directional microphone of this type is simply composed of a single metal or a plastic tube, terminated with a non-reflective material at one end and a microphone at the other end and having a row of small holes on its side. The dimension of this microphone being small, handling would be easy. By incorporating acoustic networks inside the tube various characteristics will be available.