The relationship between talker acoustics, intelligibility, and effort in degraded listening conditions

Listening to degraded speech is associated with decreased intelligibility and increased effort. However, listeners are generally able to adapt to certain types of degradations. While intelligibility of degraded speech is modulated by talker acoustics, it is unclear whether talker acoustics also affect effort and adaptation. Moreover, it has been demonstrated that talker differences are preserved across spectral degradations, but it is not known whether this effect extends to temporal degradations and which acoustic-phonetic characteristics are responsible. In a listening experiment combined with pupillometry, participants were presented with speech in quiet as well as in masking noise, time-compressed, and noise-vocoded speech by 16 Southern British English speakers. Results showed that intelligibility, but not adaptation, was modulated by talker acoustics. Talkers who were more intelligible under noise-vocoding were also more intelligible under masking and time-compression. This effect was linked to acoustic-phonetic profiles with greater vowel space dispersion (VSD) and energy in mid-range frequencies, as well as slower speaking rate. While pupil dilation indicated increasing effort with decreasing intelligibility, this study also linked reduced effort in quiet to talkers with greater VSD. The results emphasize the relevance of talker acoustics for intelligibility and effort in degraded listening conditions.