Interaural attenuation for Sennheiser HDA 200 circumaural earphones.

Interaural attenuation (IA) was evaluated for pure tones (frequency range 125 to 16000 Hz) using Sennheiser HDA 200 circumaural earphones and Telephonics TDH-39P earphones in nine unilaterally deaf subjects. Audiometry was conducted in 1-dB steps using the manual ascending technique in accordance with ISO 8253-1. For all subjects and for all tested frequencies, the lowest IA value for HDA 200 was 42 dB. The present IA values for TDH-39P earphones closely resemble previously reported data. The findings show that the HDA 200 earphones provide more IA than the TDH-39P, especially at lower frequencies (<or=500 Hz). It is concluded that contralateral masking should be applied during pure-tone audiometry with the HDA 200 earphones when the level at the test ear is more than 40 dB above the threshold of the non-test ear.