Development of a Calibrator for Simultaneous Calibration of Multiple Microphones on an Acoustic Energy Density Probe

This paper presents the theory, design, and development of a microphone calibrator used to calibrate multiple microphones simultaneously. This work was done in conjunction with the development of an acoustic energy density (ED) probe, which is used to measure the acoustic pressure and particle velocity of a sound field. The probe of interest in this paper was developed to measure ED using multiple microphones to acquire the data needed to compute the ED quantity. The microphones used are 1⁄4 inch electret microphones which do not have an ideal “flat” response over a wide range of frequencies. These characteristics prompted the need for calibration. The idea behind the calibration process was to simultaneously subject each microphone on the probe to the same known acoustic pressure and frequency. This is done using equal length small diameter tubes connected to a single source and each microphone independently. It has been shown that the microphones on the probe can be calibrated within 0.5 dB up to 2000 Hz which is the frequency range of the probe.