HESP Seminar Series: Beth Rosen, HESP Honors Defense
Title: "Effect of frequency region on across-channel processing of interaural level differences"
Abstract: Binaural interference occurs when a spectrally remote diotic interfering sound affects the ability to detect changes in interaural differences in a target sound. For interaural time differences, the magnitude of binaural interference depends on the target and interferer frequencies. For interaural level differences (ILDs), it is unclear if the magnitude of binaural interference depends on target and interferer location. ILDs are highly frequency dependent; ILDs become larger for increasing frequency for sources in the free field. Therefore, we hypothesized that binaural interference for ILDs would be frequency dependent, and that both target and interferer frequency would affect thresholds. In ten young normal-hearing adult participants, we measured ILD discrimination thresholds using single tones, once with no interferer and then in the presence of a diotic interferer. Using five frequencies (0.5, 1, 2, 4, and 8 kHz), each combination of target and interferer frequency was tested. For targets alone (without interferers), ILD just noticeable differences (JNDs) showed marginal frequency dependency. For targets with interferers, binaural interference occurred and the magnitude changed depending on the target frequency with the most interference occurring for a 2-kHz target and the least interference occurring for an 8-kHz target. The effect of interferer frequency was not significant, likely a result from the large inter-individual variability observed. These data will contribute to better understanding of across-frequency ILD processing, which is important for bilateral cochlear-implant users who rely on ILDs to localize sounds.