Some Vibrational Properties of a Stretched Circular Membrane

Abstract

In the electro-acoustic energy transformation mechanism of the electro-static type applied in the condensor microphone, the saturation phenomenon, unavoidable in the electro-magnetic type, does not appear. The electro-static type makes it possible to use an extremely thin diaphragm as far as the material strength and fabrication technique permit. Accordingly a very light weight moving part can be realized in the electro-static type transducer which can operate at high frequency up to several tens kHz if so desired. This electro-static type transducer is expected to be put into practical use extensively. The vibration membrane which is a part of the transducer can be widely applied. From these standpoints, this paper presents the design data for the vibrating membrane. The conventional solution of membrane has been mainly adopting the expansion form by using the normal function method. This solution was very effective in the examination of the physical characteristics of membrane vibration, but it was not suitable for numerical calculation since the convergency was very poor. This paper adopts the direct solution method for the equation of motion not dependent on the expansion form, which becomes effective for numerical calculation. The solution thus obtained was processed by a computer in order to generate detailed design data. Only the principal data were introduced this time among a vast amount of design data.