P61 Does the effect of sound sources diffuseness on speech perception change with age and linguistic experience?
Studying the effect of sound source diffuseness level on speech recognition has increasing importance due to the growing use of amplification systems. When an auditory stimulus is amplified and presented over multiple, spatial-separated loudspeakers, the signal’s timbre is altered due to comb filtering. In a previous study we examined how increasing the diffuseness of the sound sources might affect listeners’ ability to recognize speech presented in different types of background noise. We found that listeners performed similarly when both the target and the masker were presented via a similar number of loudspeakers. However, performance improved when the target was presented using a single speaker (compact sound source) and the masker from three (diffuse sound source) but worsened when the target was diffuse, and the masker was compact. In the current study, we extended our research to examine whether the effect of timbre changes with age and linguistic experience. Twenty-four older adults whose first language was English (Old-EFL) and 24 younger adults whose second language was English (Young-ESL) were asked to repeat sentences presented in either noise, babble, or speech. Participants were divided into two experimental groups: (1) A Compact-Target Timbre group where the target sentences were presented over a single loudspeaker, while the masker was either presented over three loudspeakers or over a single loudspeaker; (2) A Diffuse-Target Timbre group, where the target sentences were diffuse while the masker was either compact or diffuse. The results indicate that the Target Timbre has a negligible effect on thresholds when the timbre of the target matches the timbre of the masker in all three groups. When there is a timbre contrast between the target and the masker a significant separation between the compact target and diffuse target conditions’ thresholds is evident in all three groups when the masker is noise. However, for Speech and Babble Maskers, the advantage held by compact targets is severely diminished in the Young-ESL group compared to the two EFL groups.