Our long term goal is to describe the binaural processing of interaural cues in the presence of an additional acoustic input (masker) and relate this to the binaural process of signal selection. One of the more common problems associated with hearing impairment is the lack of ability to understand speech in the presence of background noise. The results of the proposed experiments will lead to a greater understanding of how the normal binaural system performs in noise. The experiments described are designed to study a variety of binaural phenomena. First, we shall continue to explore the effects of an additional acoustic input on interaural time discrimination. We will do this by 1) measuring the effect of interaural signal-masker configuration on dicrimination of interaural time differences in a temporal masking paradigm, 2) determining the masking pattern for binaural detection and analysis as a function of level, first to determine how it compares to the monaural masking pattern, and second, to measure the effect of partial masking on binaural analysis when signal and masker differ in frequency, and 3) studying the relative effects of signal sensation level and signal sound-pressure level on precision of interaural time discrimination. The second category of experiments is designed to measure the additivity of interaural cues. Specifically, we are interested in knowing if subthreshold interaural time and intensity cues will sum so as to be detectable. All data will be collected on human subjects using standard psychophysical procedures.
