A novel paradigm to define functional spatial boundaries

Abstract

One approach to studying an individual’s binaural function is to measure speech reception ability for spatially separated compared to co-located competing speech streams. This spatial-release-from-masking (SRM) task has been widely adopted due to its capacity to detect abnormal binaural function, but it has its limitations in interpreting individual spatial abilities. Here, we introduce a modified SRM task that directly measures the needed spatial separation between target and maskers to achieve a specific SRM. Stimuli were presented from 24 speakers in the free field using an equal power panning method. Normal-hearing listeners (n = 10) were tasked with identifying digits in a target stream of monosyllabic words always presented from the front. Initial measures were made using the classic SRM paradigm in which two opposite-gender masker streams were either presented from the front (co-located), or symmetrically from 30° (fixed-separation), to determine a speech reception threshold (SRT; in dB target-to-masker ratio). Based on the co-located SRT, the task then adaptively tracked the separation angle needed to achieve 6-dB SRM. Results showed for most listeners, a 10-dB SRM at 30° separation and an average spatial boundary less than 30 degrees when fixed at 6-dB SRM. [Work supported by NIH NIDCD R21DC017832 to EJO.]