Microphones and Their Calibration

The condenser microphone continues to be the standard against which other microphones are calibrated. A brief discussion of the theory of the condenser microphone, including its open-circuit voltage, electrical transfer impedance, and mechanical response, is given. The most precise method of calibration, the reciprocity pressure calibration method for laboratory standard microphones is discussed in detail, beginning with the principles of the reciprocity method. Corrections for heat conduction, equivalent volume, capillary tube, wave motion, barometric pressure and temperature are necessary to achieve the most accurate open-circuit sensitivity of condenser microphones.