This specification describes types of laboratory microphones whose properties as standards are in accordance with the best practice of the art and which are intended for use as acoustic measurement standards. These microphones lend themselves to calibration in absolute terms by the reciprocity method as specified in Appendix II.

In the microphones now in current use, the motion of the pressure-sensitive element (diaphragm) is stiffness-controlled over the major portion of their operating frequency range and the output impedance of the microphone is essentially capacitive. The essential differences among the types of microphones herein described are in the frequency and sound pressure range over which each is to be used. The specific differences in characteristics are as described in Sections 3 and 4.

This specification is not intended to preclude the use of other types of microphones whose performance characteristics meet the requirements of this specification.