A quasi-free-field transducer system for high-frequency audiometry.

Previous attempts to measure human hearing capacity in the high frequencies (8 to 20 kHz) have only been met with rather limited success. Based on the results of Shaw and co-workers we have developed a free-field transducer system where the stimuli are delivered from a point source and meet the ear as plane progressive waves at a carefully chosen angle of incidence. The system can be calibrated in a precise manner by means of a specially designed coupler. Preliminary results indicate that the procedure is easily applicable also in a group of inexperienced test subjects and the test-retest variability was within such limits that are acceptable for subjective audiometric testing. These results require validation in a large group of subjects and we hope it will be possible to establish normative values for various age groups.