During her doctoral research, Adank designed an automated expert listener, which can determine differences in the pronunciation of Dutch vowels. The researcher discovered that acoustic methods such as the pitch could describe the differences in pronunciation just as well as phonetic translations. The use of acoustic methods can save a lot of time.
The researchers recorded the speech of 160 Dutch and Flemish teachers of Dutch at high schools in different regions. For example the teachers had to read aloud sentences, each of which contained a different vowel, such as "In soes en soeze zit de oe".
The researcher used acoustic measurements to recognise the differences in pronunciation. In addition to this ten experts produced a phonetic transcription of these vowels. The acoustic measurements were then compared with the phonetic transcriptions. This comparison revealed that it is perfectly possible to use acoustic measurements to map differences in the pronunciation of vowels.
With acoustic methods the researchers measure, for example, the pitch or the formants. A formant is an enhanced frequency characteristic for a certain phoneme. Acoustic measurements cost little time and are easy to replicate. However, a disadvantage of the acoustic method is that it cannot take into account anatomical and physiological differences between speakers.
For example, the frequency of the zero formant or fundamental tone is twice as high in women as in men. Similar effects also exist for characteristics such as body size: smaller people produce higher fundamental tones. Adank eliminated these person-related differences, leaving just the sociological differences in pronunciation.
The phonetic method determines differences in pronunciation by allowing experts to manually make phonetic transcriptions. The experts indicate a difference in the pronunciation of the vowels by describing the position of the jaw, tongue and lips: the 'e' in the Dutch word 'pet' is pronounced with the tongue protruding forwards in the mouth, with a lowered jaw and with slightly spread lips. In this manner differences in pronunciation can be established with a high degree of accuracy. However, this method costs a lot of time. Furthermore, little is known about the reliability of the analyses.
Patti Adank's research is part of a joint Dutch-Flemish research project that aims to map differences in the pronunciation of Dutch and Flemish.
For further information please contact Dr Patti Adank (Department of Language and Speech, University of Nijmegen), tel. 31-24-361-2055, fax 31-24-361-2907, e-mail: p.adank@let.kun.nl, internet http://lands.let.kun.nl/staff/staffPERperson.php3?name=adank. The doctoral thesis was defended on 23 June 2003. Ms Adank's supervisor was Prof. R.W.N.M. van Hout.
The research was funded by the Netherlands Organisation for Scientific Research and the Fund for Scientific Research - Flanders (Belgium).