ASA 124th Meeting New Orleans 1992 October

1aEA12. Electrostatic actuator method for calibration of high- temperature fiber-optic microphones.

Trung D. Nguyen

Oscar Gonzales

ECE Dept., Old Dominion Univ., Norfolk, VA 23508

Allan J. Zuckerwar

NASA---Langley Res. Ctr., Hampton, VA 23665

A fiber-optic lever microphone has been developed for high-temperature applications. The sensitivity of the microphone is determined from a pistonphone calibration at room temperature. The electrostatic actuator method is used for the frequency response calibration of the microphone at room temperature and 1000 (degrees)F. The microphone is placed inside an oven, and is excited by the electrostatic force between the actuator electrode and the microphone membrane. The frequency response of the microphone, along with the background noise, is analyzed on an FFT analyzer. For a 0.072 in. diameter of the membrane, the typical sensitivity of the microphone is 1.3 (mu)V/Pa, and the typical bandwidth is 47 kHz. The background noise includes contributions from the microphone and the photodetector, in which the shot noise is the dominant source of noise.