The accuracy of the electrostatic actuator method of determining the frequency response of condenser microphones

Abstract

Measurements have been made of the difference between the frequency response of a condenser microphone as determined by the electrostatic actuator method, and the true response as determined by the closed coupler reciprocity method. Results are given for Bruel & Kj˦r microphones type 4144, 4145 and 4134 and the manufacturer's actuators. Methods of reducing the difference, and the effect on the difference of a perforation in the diaphragm, have been investigated. A procedure is suggested for ensuring the validity of actuator calibrations at low frequencies.