When we produce different vowel qualities, we change the vocal-tract configuration by moving our speech organs. The following are the midsaggital cross-sections of the vocal-tract configuration for the five Japanese vowels (left), and their schematic straight models (right):
From this figure, we can see the following:
– Vowel /i/: there is a narrow constriction in the front cavity, whereas the back cavity has a certain volume.
– Vowel /e/: as with vowel /i/, there is a narrow constriction in the front cavity, but the degree of the constriction is less than that of vowel /i/.
– Vowel /a/: the lips (and the front cavity) are widely open, whereas there is a narrow constriction in the back cavity.
– Vowel /o/: like vowel /a/, there is a narrow constriction in the back cavity, but the degree of the lip opening is rather small.
– Vowel /u/: there is a narrow constriction in the middle of the vocal tract; in addition, the degree of the lip opening is small.
Chiba and Kajiyama (1941) made vocal-tract models based on their measurements. By feeding a glottal sound into their models, they demonstrated that the vowel sounds produced by the models are close to their naturally produced counterparts. Arai (2001) replicated their models in 2001 for the 60th anniversary of the publication of The Vowel by Chiba and Kajiyama (1941). The following are Arai’s “cylinder-type” vocal-tract models:
Let’s listen to vowels sounds produced from the models. An electrolarynx is used to generate the glottal sound. First you will hear the glottal sound.
The glottal sound in isolation sounds like a buzz. However, once the glottal sound is fed into a vocal-tract model, you will hear the quality of vowel change.
- Arai, T., “The replication of Chiba and Kajiyama’s mechanical models of the human vocal cavity,” Journal of the Phonetic Society of Japan, 5(2), 31-38, 2001.
- Arai, T., “Education system in acoustics of speech production using physical models of the human vocal tract,” Acoustical Science and Technology, 28(3), 190-201, 2007.
- Chiba, T. and Kajiyama, M., The Vowel: Its Nature and Structure, Tokyo-Kaiseikan Pub. Co., Ltd., Tokyo, 1941.