The effect of lombard speech modifications in different information density contexts

Speakers adapt their speech to increase clarity in the presence of background noise (Lombard speech) [1, 2]. However, they also modify their speech to be efficient by shortening word duration in more predictable contexts [3]. To meet these two communicative functions, speakers will attempt to resolve any conflicting communicative demands. The present study focuses on how this can be resolved in the acoustic domain. A total of 1520 target CV syllables were annotated and analysed from 38 German speakers in 2 white-noise (no noise vs. -10 dB SNR) and 2 surprisal (H vs. L) contexts. Median fundamental frequency (F0), intensity range, and syllable duration were extracted. Our results revealed effects of both noise and surprisal on syllable duration and intensity range, but only an effect of noise on F0. This might suggest redundant (multi-dimensional) acoustic coding in Lombard speech modification, but not so in surprisal modification.