It is known that speech changes with speech styles and acoustic environments. This study examined the hypothesis that the phonological contrast between Japanese stops is influenced by environments with noise and reverberation. To investigate this, we controlled for speech style, either casual or “clear speech,” within each environment and examined how noise and reverberation affect the production of Japanese stops by native Japanese speakers. In the experiment, participants produced sentences in quiet, noisy, and reverberant environments. The target words were real Japanese words with two or more morae and a stop consonant (/p/ or /b/) in word-initial position. Their pitch accent was either High-Low or Low-High. The results showed the following: First, there was individual variation in the occurrence rate of prevoicing before the burst in /b/. Second, regarding the duration from the burst to the onset of the following vowel, all participants showed a clear difference between /b/ and /p/ across all pitch accent types, speech styles, and environments. Third, with respect to the fundamental frequency at the onset of the following vowel, some participants exhibited consistent changes related to the /b/-/p/ contrast across all experimental conditions.
Kawai et al. (Wed,) studied this question.