Studies on the Air Pressure in the Vocal Tract during Phonation

Abstract

The intra-nasal, intra-oral and subglottic air pressures were measured during production of various Japanese speech sounds, andd these values of pressure were compared with the sonagrams of each sound in degree as well as in time relation.A new electromanometer, in which the mechanical pressure is changed to the electrical energy with strain guage, was used in order to record delicate changes of the pressure corresponding to each component of speech sounds.Both speech sound and air pressure were traced on the electrical oscillograph and simultaneously the former recorded with a tape-recorder to be analysed on the sonagram.The results obtained are as follows.[I] On the intra-nasal air pressure1. The intra-nasal air pressure does not rise so markedly except during production of nasal syllables. The pressure begins to rise ca. 35-50msec. prior to the phonation and reaches its maximum value 7-13mm H2O at the end of the nasal consonant and then it drops rapidly at the following vowel.2. During phonation of some vowels such as “i” or “u”, a slight rise of the intranasal air pressure is occasionally observed.[II] On the intra-oral air pressure1. The intra-oral air pressure is not observed to rise during phonation vowels or nasal syllables.2. The intra-oral air pressure begins to rise almost simultaneously with the utterance of voiced consonant syllables, i. e. with its proceeding wave. The maximum value (5-7mm H2O) of the pressure is observed at the end of the voiced consonant wave in the fricative sounds and at the beginning in the plosive sounds.3. The intra-oral air pressure begins to rise 60-80msec. prior to the phonation of the voiceless fricative consonant syllables and 170-210msec. prior to the plosives. The maximum value (7-9mm H2O) of the pressure is observed at the point of 1/4 or 1/5 of the consonant wave in the fricative sounds and at the end in the plosive sounds.4. The pressure drops rapidly at the following vowels in the both voiceless and voiced consonant syllables.[III] On the subglottic air pressure1. The subglottic air pressure rises during phonation of all speech sounds, and its maximum value is almost the same, showing the height of 30-50mm H2O.2. The subglottic air pressure begins to rise prior to the production of every speech sound. This phenomenons considered to show the “Kaiser's Effect”, and the latent period between onset of subglottic pressure and voice production varies according to speech sounds, i. e. it shows 170-190msec. in voiced vowels, 80-90msec. in nasals, 90-110msec. in voiced fricatives, 80-120 msec. in voiced plosives, 80-100msec. in voiceless fricatives and 160-190 msec.in voiceless plosive, sounds.3. There is also a difference in the way of elevation of the subglottic air pressure among speech sounds. During phonation of vowels and voiced plosive consonant syllables, the curve of ascending subglottic pressure to be traced on oscillograph is more convex, on the contrary, is more concave in nasals and voiced fricative consonants. During phonation of voiceless consonant syllables the subglottic air pressure continues to rise to the production of following vowels, but in the course a transient slight drop is always observed. This drop of air pressure corresponds to production of the transitional part of consonant syllables and follows to the time when the intra-oral air pressure shows its maximum value.