ASA 125th Meeting Ottawa 1993 May

1pEA2. Some recent developments in phase match of microphones.

George S. K. Wong

Inst. for Natl. Measurement Standards, Natl. Res. Council Canada, Ottawa, ON K1A 0R6, Canada

Phase match data for condenser microphones obtained with a new coupler are discussed. The protective grids of the microphones have some influence on the phase match at frequencies above 1 kHz. The phase match theory is based on the exchange microphone method [J. Acoust. Soc. Am. 90, 1253--1255 (1991)], which is also capable of discerning the phase match between the amplifiers of the two measuring channels. The performance of the coupler is verified with direct electrical measurement of the phase difference between the two channels and by comparison with the corresponding measurements provided by the coupler. A comparison is made between the data obtained with the coupler and those acquired with the electrostatic actuator method. Since the electrostatic actuator method does not expose the microphone back cavity pressure equalizing vent to the same excitation, the phase match readings provided by the electrostatic actuator method are confirmed to be not valid, particularly at low frequencies.