Benefit from spatial separation of multiple talkers in bilateral hearing-aid users: Effects of hearing loss, age, and cognition.

To study the spatial hearing abilities of bilateral hearing-aid users in multi-talker situations, 20 subjects received fittings configured to preserve acoustic cues salient for spatial hearing. Following acclimatization, speech reception thresholds (SRTs) were measured for three competing talkers that were either co-located or spatially separated along the front-back or left-right dimension. In addition, the subjects' working memory and attentional abilities were measured. Left-right SRTs varied over more than 14 dB, while front-back SRTs varied over more than 8 dB. Furthermore, significant correlations were observed between left-right SRTs, age, and low-frequency hearing loss, and also between front-back SRTs, age, and high-frequency aided thresholds. Concerning cognitive effects, left-right performance was most strongly related to attentional abilities, while front-back performance showed a relation to working memory abilities. Altogether, these results suggest that, due to raised hearing thresholds and aging, hearing-aid users have reduced access to interaural and monaural spatial cues as well as a diminished ability to 'enhance' a target signal by means of top-down processing. These deficits, in turn, lead to impaired functioning in complex listening environments.