Evaluation of spatial and spectro-temporal cues in release from masking in normal hearing listeners

Abstract

ObjectiveNormal-hearing listeners use spatial cues to segregate target sounds from concurrent multiple sources. This phenomenon is known as the auditory spatial release of masking (SRM). Auditory spatial cues involve interaural time difference (ITD) and interaural level difference (ILD) affected by spectral and temporal features. Thus, to reveal factors influencing the SRM, the present study was conducted to investigate the effects of the frequency and ongoing duration on the lateralization (ITD and ILD). Also, this research examined the mutual effects of spatial separation, duration, and frequency on the SRM in spatial locations in virtually azimuth 0, ±45 and ±90 degrees. Methods: Twenty normal-hearing listeners were tested for ITD and ILD thresholds and auditory release of masking in spatial locations in azimuth 0, ±45 and ±90 degrees. Stochastic figure-ground (SFG) stimuli were utilized with low- and high-frequency figures and different durations. Results: ITD threshold was not affected by ongoing duration and frequency but the ILD threshold decreased with increasing the duration. A duration of 200 ms had the least SRM and further duration had roughly a flat trend. SRM was prominent in short and long durations between the spatial location in azimuth 0 and ±45 degrees but not in median durations in low-frequency figures (p < 0.05). Conclusion: it can be concluded the ILD threshold (not ITD threshold) is dependent on ongoing duration. In every spatial location in azimuth, a duration of 200 ms had the least SRM and SRM observed with variation of the location in azimuth 0 to ±45 degrees in short and long durations that is prominent for low-frequency figures.