Patterns of linguopalatal contact during Japanese vowel devoicing

It is widely claimed that close vowels in Japanese are devoiced when they occur between voiceless consonants. In this paper, voiceless vowels are represented symbolically as [V-] and voiced vowels as [V+]. The patterns of linguopalatal contact during C[V-]C units and the corresponding C[V+]C units are examined using the method of electropalatography (EPG). Our results show that C[V-]C units and the corresponding C[V+]C units often differ with respect to: (1) the amount (patterns) of tongue-palate contact from C1 (the preceding consonant) to C2 (the following consonant) and (2) the articulatory time interval from C1 to C2. Generally, the amount of linguopalatal contact is significantly greater at the front part of the palate in C[V-]C units compared to the corresponding C[V+]C units. The articulatory time interval from C1 to C2 is generally shorter in C[V-]C units compared to the corresponding C[V+]C units, though this is not always the case for all consonantal types. However, the articulatory gesture of the vowel appears to exist between voiceless consonants regardless of whether they are voiced or devoiced. Devoiced vowels have often been examined from the aspect of the opening gesture of the glottis since a turbulent noise during devoiced vowels is expected to be made at the glottis. However, our study seems to suggest that a turbulent noise can also be produced in the oral cavity as well as at the glottis by increasing the degree of tongue-palate contact. In principle, it is expected that the larger the tongue-palate contact is, the greater the turbulent noise will become due to the increased rate of airflow. This kind of linguopalatal contact appears to be a positive effort of a speaker rather than simply a matter of a shorter articulatory time interval in C[V-]C units: both factors seem to be related to the production of vowel devoicing, which seems to suggest that aerodynamic effects are involved.