Acoustic-phonetic characteristics of speech produced with communicative intent to counter adverse listening conditions.

This study investigated whether speech produced in spontaneous interactions when addressing a talker experiencing actual challenging conditions differs in acoustic-phonetic characteristics from speech produced (a) with communicative intent under more ideal conditions and (b) without communicative intent under imaginary challenging conditions (read, clear speech). It also investigated whether acoustic-phonetic modifications made to counteract the effects of a challenging listening condition are tailored to the condition under which communication occurs. Forty talkers were recorded in pairs while engaged in "spot the difference" picture tasks in good and challenging conditions. In the challenging conditions, one talker heard the other (1) via a three-channel noise vocoder (VOC); (2) with simultaneous babble noise (BABBLE). Read, clear speech showed more extreme changes in median F0, F0 range, and speaking rate than speech produced to counter the effects of a challenging listening condition. In the VOC condition, where F0 and intensity enhancements are unlikely to aid intelligibility, talkers did not change their F0 median and range; mean energy and vowel F1 increased less than in the BABBLE condition. This suggests that speech production is listener-focused, and that talkers modulate their speech according to their interlocutors' needs, even when not directly experiencing the challenging listening condition.