Monaural and Binaural Discrimination against Competing Sentences

PB-50 lists were presented in a sound field against a background of spoken sentences. Four signal-to-noise ratios plus one quiet condition were used. Test items came from a loudspeaker to one side of the subject and competing sentences from a second loudspeaker, on the opposite side. Sixteen normal hearers underwent both test and retest under one binaural and two monaural conditions. Discrimination functions for these conditions showed similar configurations, but were displaced from one another along the signal-to-noise axis. Head-shadow effects caused poorer discrimination during monaural listening when test items come from the far side of the head. Monaural efficiency with the open ear facing the source of test items was almost as good as binaural efficiency. However, binaural performance here exhibited an advantage equal to approximately a 3-dB shift in signal-to-noise ratio, despite the fact that the head-shadow effect enhanced interference in the far ear by almost 13 dB. Work supported by the Veterans' Administration and by the National Institute of Neurological Diseases and Blindness, National Institutes of Health, U. S. Department of Health, Education, and Welfare.