抄録
A study is made on various condenser microphones, each of which consists of a metallic back plate and a thin plastic film stretched over the back plate, being in direct touch with it at a number of points. The surface of the back plate has been roughened or provided with grooves, hollows or holes, while the external surface of the plastic film has been made conductive by metallizing it.
The microphones are calibrated in the frequency range 1.5∼150 kc/s. A fair agreement is found between the classifications of the back plates according to the mechanical roughnesses of the surfaces and the classifications based upon the frequency responses of the microphones. It is shown that the microphones with the back plates having finely roughened surfaces can be considered as single resonance systems.
Detailed data are given, with which a microphone having a flat frequency response up to a desired high frequency below 150 kc/s can be easily constructed.
