A. note on determination of the diffuse-field sensitivity ofmicrophones using the reciprocity technique

摘要

The diffuse-field response of a microphone is usually obtained by adding a random-incidencecorrection to the pressure response of the microphone. However, the random-incidence correction isdetermined from a relative measurement, and its accuracy depends not only on the relative responseat all angles of incidence but also on the accuracy of the frequency response at normal incidence.By contrast, this paper is concerned with determining the absolute diffuse-field response of amicrophone using the reciprocity technique. To examine this possibility, a reciprocity calibrationsetup is used for measuring the electrical transfer impedance between a pair of microphones placedin a miniature (2 m3) reverberation room. The transfer function between the microphones ismeasured using fast Fourier transform analysis and pseudorandom noise. The calculation of thediffuse-field sensitivity involves (a) separation of the reverberant response from the total response,(b) determination of the reverberation time, and (c) averaging over space and frequency. Theresulting diffuse-field correction is compared with an estimate of the random-incidence correctiondetermined in an anechoic room and with a numerical prediction.