HESP Seminar: Allison Choi (HESP)

On the level dependency of across-frequency binaural interference

Undergraduate Honors Thesis Defense

Abstract: Binaural hearing enables listeners to localize sound in the horizontal plane, even when dealing with intricate speech-like signals characterized by distributed energy across a broad range of frequencies and varying sound pressure levels. Low-frequency interaural time differences (ITDs) are the most important cue for human horizontal-plane sound localization. Across-frequency binaural interference tasks (where changes in ITD discrimination thresholds of a target signal are measured in the presence of a remote interferer signal) can be used to measure how a listener weighs different frequency regions for ITD. While it is known that low-frequency (0.5 kHz) targets experience less binaural interference from higher-frequency (4 kHz) interferers than vice versa, the impact of the relative level of the two signals has remained mostly unexplored. ITD discrimination thresholds were measured in normal-hearing listeners with target/interferer intensities of 35, 55, and 75 dB-A and frequencies of 0.5, 4, and 8 kHz. For the 0.5-kHz target and 4-kHz interferer, the effects of interferer level were confined to the 35-dB target. For the 4-kHz target and 0.5-kHz interferer, there were significant main effects of target level and interferer level but not the interaction. The results suggest that the amount of binaural interference is mostly dependent on the target frequency and target level.