Comparison Calibration of Piezoresistive Microphones for Acoustic Power Measurements.
NAVAL POSTGRADUATE SCHOOL MONTEREY CA
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A calibration of two Endevco piezoresistive microphones was carried out under static and dynamic pressures. The dynamic pressure calibrations were done by comparison with a B and K condenser microphone. The calibration was carried out in a small closed volume in air and helium. In helium, the closed volume was pressurized to atmospheric pressure and then 10 Atm. The dynamic calibration would determine the flatness of the calibration curve, as well as determine a sensitivity value over the range of frequencies used. The results showed that the calibration curve for the piezoresistive microphones are flat from static pressures to about 300 Hz and then begin to fall off. The value of the sensitivity of the flat region of the calibration curve for one microphone was within 0.4 of the value for sensitivity calculated under the static pressure calibration. For the other microphone the static and dynamic sensitivities were within 1.3 of each other. Thus, the static calibration of one microphone may be used under dynamic conditions with a less than 1 error while using the other microphone similarly will produce an error of greater than 1.
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