Proposed transfer-function technique for earphone analysis

This research was prompted by the need to select a suitable headset for auditory processing of passive-sonar information. The selection of an accurate transducer for auditory processing of passive sonar signals requires accurate measurement of frequency response. No standard for such measurement exists. The method proposed here uses a modified Zwislocki acoustic coupler mounted in an anthropometrically and acoustically average mannikin, KEMAR, in order to simulate the acoustic load that an average human ear would place on the earphone element. A computerized signal-collection and -analysis system substracted this transfer function from stored earphone-response data. Responses were averaged across samples of left and right earphone elements and across repeated measurements that sampled variability due to headset placement, seal around the ear, and headband tension. Analog plots of earphone frequency response were indistinguishable from computer regenerated plots of that same frequency response. Comparison of raw data and corrected data show the correction procedure to be within 0.2 dB of perfect accuracy.