Peripheral hearing loss: implications for clinical dichotic listening tests.

This experiment assessed the extent to which a peripheral hearing loss may confound interpretation of dichotic listening test results in assessment of central auditory deficit. A normal-hearing listener was tested monotically and dichotically with CV nonsense syllables in two conditions. In one, an EAR plug was inserted in the auditory canal to simulate a unilateral conductive hearing loss. In the second, no plus was inserted. Syllables were presented with equal intensity to the two ears for dichotic testing and testing was conducted at several different intensities. With the plug inserted, both magnitude and direction of percent ear advantage varied with test intensity even when monotic speech recognition scores exceeded 95% for both ears. When dichotic tests are used to assess central auditory deficit in patients with peripheral hearing loss, we recommend that the test intensity be at least 10 dB from both the lower and upper knees of monotic performance-intensity functions.