Laryngeal adjustments in the production of the fricative consonants and devoiced vowels in Japanese.

The role of laryngeal adjustments for phonetic variations of voicing in Japanese--vowel devoicing and intervocalic /h/ voicing--was investigated using laryngeal electromyography (EMG) and fiberoptic endoscopy. The results indicated that the vowel devoicing was accompanied by EMG activity patterns of the posterior cricoarytenoid and interarytenoid different from those for fully voiced vowels, causing the glottis to be wide open. In this respect, it may be concluded that vowel devoicing mainly reflects a kind of free variation at a higher level than the EMG signals. In contrast, the voicing of /h/ occurred while the glottis remained as wide as it did for voiceless /h/ or /s/ with comparable EMG patterns of those muscles, despite the presence of vocal fold vibrations. Therefore, it may be that this latter phenomenon is chiefly dependent on some other condition at the level of the glottis.