Tuning in the spatial dimension: Evidence from a masked speech identification task

Abstract

Spatial release from masking was studied in a three-talker soundfield listening experiment. The target talker was presented at 0 degrees azimuth and the maskers were either colocated or symmetrically positioned around the target, with a different masker talker on each side. The symmetric placement greatly reduced any "better ear" listening advantage. When the maskers were separated from the target by +/-15 degrees , the average spatial release from masking was 8 dB. Wider separations increased the release to more than 12 dB. This large effect was eliminated when binaural cues and perceived spatial separation were degraded by covering one ear with an earplug and earmuff. Increasing reverberation in the room increased the target-to-masker ratio (TM) for the separated, but not colocated, conditions reducing the release from masking, although a significant advantage of spatial separation remained. Time reversing the masker speech improved performance in both the colocated and spatially separated cases but lowered TM the most for the colocated condition, also resulting in a reduction in the spatial release from masking. Overall, the spatial tuning observed appears to depend on the presence of interaural differences that improve the perceptual segregation of sources and facilitate the focus of attention at a point in space.

Binaural Glimpses at the Cocktail Party?

“…Similar to other studies with symmetric masker configurations (Bronkhorst and Plomp 1988;Glyde et al 2013;Marrone et al 2008), subjects benefitted strongly from a spatial separation of the maskers from the target. Most comparable to the spatial configurations tested in these studies was the current ±90°c onfiguration.…”

“…In a comparable arrangement of target (0°) and maskers (±90°), the SRM of ∼5.5 dB in the current study was smaller than in, e.g. Marrone et al (2008;∼12 dB). However, it should be noted that in their study SRM was quantified with only two maskers (all talkers female) compared to the current eight maskers of mixed gender.…”

“…In combination, these HRTF differences explain the 1.5-dB increased SRM for ±40°/±140°in comparison to ±90°. Results from Marrone et al (2008) showed virtually no change of SRM when their maskers were moved from ±90°to ±45°, suggesting that part of the 1.5-dB benefit found in the current data might still be caused by moving four of the masker into the subjects' rear hemisphere. When all eight maskers were distributed equally around the listener, SRM did not improve further but deteriorated, relative to the ±40°/±140°configuration.…”

“…spatial release from masking (SRM), between 5 and 12 dB depending on the spatial separation of target and masker (e.g. Marrone et al 2008;Noble and Perrett 2002). One potential mechanism underlying SRM in these conditions is the binaural processing of the interaural level difference (ILD) and interaural time difference (ITD) as, e.g.…”

“…It was shown that the use of better-ear glimpses cannot fully explain SI if the task produces high informational masking (Best et al 2015;Glyde et al 2013). Moreover, Kidd et al (2010) determined SI in a symmetric speech masker configuration similar to Marrone et al (2008), when all signals where either unfiltered or filtered into low-, midor high-frequency regions. The authors showed that SRM was highest for the unfiltered broadband condition, but the filtered conditions lead to a reduced but still considerable SRM (between 5 and 7 dB), indicating that there may be other factors than better-ear glimpses influencing SI in a multi-talker environment.…”