Interaural attenuation for tubephone insert earphones.

Interaural attenuation of pure tone and speech signals was evaluated for a new audiometric insert earphone, the ER-3A tubephone, and a conventional TDH-49P supra-aural earphone in seven unilaterally deaf adult subjects. These results validate and extend the interaural attenuation data reported by the manufacturer of the ER-3A and his associates. At frequencies of 0.5 to 1 kHz, mean interaural attenuation for the deeply inserted ER-3A decreased from 94+ dB to 81 dB, with the lowest value for any subject, 75 dB. Interaural attenuation for speech approximated that of the 1 to 2 kHz frequency range. The ER-3A tubephone provides significantly greater acoustic isolation between the two ears in the low-mid frequency audiometric range than the conventional supra-aural earphone.