High-frequency air conduction audiometry. Testing of a new low impedance circumaural transducer system in normal...

A new circumaural transducer was tested in the frequency range 125 Hz to 20 kHz. The new transducer has a low acoustic impedance and loads the ear closely to free-field conditions, thus ensuring that sensitivity to different positions of the transducer around the ear is reduced compared to conventional audiometric headphones. The transducer was tested on 57 individuals (114 ears) in the age range 10 to 20 (median age 17.0 years). The results, showing a fairly good accordance with the ISO standard free-field thresholds values, seem to confirm that the new transducer system loads the ears similarly to free-field conditions. The results were also compared with the threshold values from other high-frequency investigations using different transducer systems. In order to verify the reliability of the system, a test-retest was carried out on 12 inexperienced normal individuals (24 ears) (median age 26.5 years; range values from 22 to 44 years). The standard deviations of the test-retest ranged from 2.8dB to 6.6dB. A comparison of these values with the results from other high-frequency test-retests is of dubious value, as such retests have often been performed and estimated in different ways. International standards for high-frequency audiometry threshold and international standards for test-retest procedure are needed. The increasing administration of cytotoxic drugs in the treatment of malignant diseases will increase the need for reliable high-frequency audiometry equipment.