Production and perception of velar stop (de)voicing in European Portuguese and Italian

Speech production and speech perception studies were conducted to compare (de)voicing in the Romance languages European Portuguese (EP) and Italian. For the speech production part, velar stops in two positions and four vowel contexts were recorded. The voicing status for 10 consecutive landmarks during stop closure was computed. Results showed that during the complete stop closure voicing was always maintained for Italian, and that for EP, there was strong devoicing for all vowel contexts and positions. Both language and vowel context had a significant effect on voicing during stop closure. The duration values and voicing patterns from the production study were then used as input factors to a follow-up perceptual experiment to test the effects of vowel duration, stop duration and voicing maintenance on voicing perception by EP and Italian listeners. Perceptual stimuli (VCV) were generated using biomechanical modelling so that they would include physically realistic transitions between phonemes. The consonants were velar stops, with no burst or noise included in the signal. A strong language dependency of the three factors on listeners' voicing distinction was found, with high sensitivity for all three cues for EP listeners and low sensitivity for Italian listeners. For EP stimuli with high voicing maintenance during stop closure, this cue was very strong and overrode the other two acoustic cues. However, for stimuli with low voicing maintenance (i.e. highly devoiced stimuli), the acoustic cues vowel duration and stop duration take over. Even in the absence of both voicing maintenance during stop closure and a burst, the acoustic cues vowel duration and stop duration guaranteed stable voicing distinction in EP. Italian listeners were insensitive to all three acoustic cues examined in this study, with stable voiced responses throughout all of the varying fully crossed factors. None of the examined acoustic cues appeared to be used by Italian listeners to obtain a robust voicing distinction, thus pointing to the use of other acoustic cues or combination of other cues to guarantee stable voicing distinction in this language.