Electrical cross-talk subtraction for free-field reciprocity calibration of half-inch laboratory standard microphones.

This paper presents a procedure for free-field calibration of half-inch laboratory standard microphones by reciprocity that allows the identification and removal of the electrical cross-talk, multiple backscattering, reflections, noise, and all harmonic distortion components when measuring the electrical transfer impedance between the microphones. Initially, the difficulties of free-field calibration of condenser microphones by the reciprocity method are pointed out and the state of art is summarized. Following, the proposed procedure, which allows determining microphone sensitivities in the frequency range from 1 kHz to 40 kHz, is described: The cross-talk is removed by subtraction while multiple backscattering, reflections, noise and all harmonic distortion components are removed by a time-selective technique. Measurements and results are presented and discussed. A comparison between the results obtained by the proposed procedure and the pressure field calibration results corrected to free-field shows the efficiency and accuracy of the technique.