CALIBRATION OF MICROPHONE ARRAYS FOR PHASED ARRAY PROCESSING

An array of microphones was calibrated so that it could be used to make accurate measurements of point sources. This paper describes the analysis and procedures that differ from calibrating a single microphone for accurate measurements. Calibration involves the phase of all microphones and electronic instrumentation and the amplitude and directivity response of the entire array. Procedures include measuring the phase response of the instrumentation, phase checking with a point source, calibrating a source in an anechoic chamber and using the calibration source to calibrate the array for amplitude and for directivity. Results show good phase fidelity, a frequency dependent amplitude deviation from a simple free-field microphone and fairly smooth directivity characteristics that can be corrected with a non-linear neural net model. Nomenclature