Abstract:
A direct method for determining free-field microphone sensitivities is described which allows one to obtain primary calibration and comparison with standard reciprocity technique. By scanning the menmbrane surface for inspection of vibration patterns, it is furthermore possible to evaluate the beghaviour of the membrane clamped to the microphone housing. The method is based on the reciprocity principle but different from the standard reciprocity method. Instead, it involves only a direct absolute measurement of the driving current and the membrane velocity by laser-optical instrumentation.