Diffuse-field reciprocity calibration of half-inch laboratory standard microphones using simultaneous reverberation time measurement.

Abstract

This paper presents a procedure for diffuse-field calibration of half-inch laboratory standard microphones by reciprocity using three microphones and a small reverberation chamber. The procedure consists of obtaining the impulse response of the system microphone-chamber-microphone and employing it to determine both the electrical transfer impedance between the microphones and the chamber's reverberation time (necessary to calculate the acoustic transfer impedance between the microphones). The electrical transfer impedance is calculated from the reverberant part of the obtained impulse response and the reverberation time is obtained by integrating the same impulse response. A comparison between results obtained by the proposed procedure (by the reciprocity method) and pressure field results corrected to diffuse-field (an usual alternative method) shows the accuracy of the proposal, while a comparison with other diffuse-field procedures using the reciprocity method shows that the measured frequency range is extended down, whereas similar performance is found in the common range.