Constructing a three-dimension physiological vowel space of the Mandarin language using electromagnetic articulography

The spatial relations of vowels are traditionally depicted by using an acoustic quadrilateral. However, the accuracy of vowel chart has been controversial. In the present study, the lingual movements of different mandarin Chinese vowels were investigated using electromagnetic articulography (EMA, AG501) and the physiological equivalent of Chinese vowels was then developed and compared to the traditional acoustical vowel quadrilateral. Six native mandarin speakers repeated each one of the six vowels (/a/, /o/, /Υ/, /i/, /u/ and /y/) by four times. The key region of each vowel, which was characterized by x, y, z tongue position at the intermediate temporal point of vowel pronunciation, was extracted. The tongue movement distance was calculated between the key region of each vowel and static tongue position. Clustering method was used to find out the centroid of the distances for each vowel. It was found that there are considerable differences between the actual lingual positions and acoustic quadrilateral's relative position depictions in the pronunciation of vowels like /u/. Results indicated that acoustic quadrilateral was insufficient to describe the lingual movement information of vowels pronunciation.