1.2 Purpose and the scope of this study
Developments in the field of speech production have shed new light on the understanding of the underlying mechanisms of vowel production and provided us with new insights for examining and reinterpreting the linguistic vowel features.However, what should be pointed out is that previous researches on vowel production are mostly theoretically orientated.Little effort has been made to explore vowel production thoroughly in a specific language.The articulatory mechanisms for vowel distinctions are far from clear.For instance, it still remains unclear how the primary vowel features such as vowel height and backness are correlated with vowel articulation and can thus be interpreted from a linguistic point of view.Although they have been well interpreted in the acoustical or psycho-acoustical domain, vowel height and backness need an explicit explanation in the articulatory domain as well, i.e., through what kinds of articulatory mechanisms are these acoustical distinctions achieved? Thus, a close examination of vowel production in a specific language is of great importance.On the one hand, it gives a whole picture of vowel production in that particular language, making it possible to interpret the linguistic vowel features in both acoustical and physiological domains, and on the other hand, the empirical production data can be used to test the validity of the current theories of vowel production.
The present study is an acoustic and articulatory investigation of vowel production in Ningbo Chinese.The purpose is twofold.On the one First, the study is empirical, and aims to ascertain how the vowel system of a language can be described in the acoustic or articulatory domain or both.Second, it explores the relationship between the acoustic and articulatory aspects of vowel production based on the observed cmpiriuldnta.As mentioned earlier, previous studies have shown that phonological vowel description such as height and backness is based on acoustical or psycho-acoustical characteristics, though it remains unclear how acoustic goals are achieved with articulatory gestures.As only a few vowels （in most cases, only the three point vowels） of a few languages （mainly English or other a few European languages） were examined in past studies, this study is intended to contribute to a more comprehensive knowledge of the articulatory mechanisms and their acoustical consequences during vowel production.The Ningbo Chinese has several advantages for investigating vowel production.First, it has a rich inventory of monophthongs and diphthongs.Second, most of the vowels in Ningbo can constitute meaningful monosyllabic wordsby themselves and thus are free from consonantal influences.Third, the vowels in the Ningbo Chinese do not contrast in tenseness.Also, there are phonetic short vowels in Ningbo.Thus it avoids the complexity brought out by tenseness distinction, while the data also provides an opportunity to explore the phonetic difference in quantity between vowels.
In addition to the questions concerning vowel features of height and backness, the scope of the present study covers the following issues：
（1） Vowel distinction in lip gestures.In most languages of the world, the lip gesture of vowels is either predictable （front vowels are usually unrounded and back vowels are usually rounded） or contrasts in roundedness.It is reported that there is a three-way distinction of lip rounding for the high vowels in Swedish （see 2.3.1.4 for discussion in length and Ladefoged ＆ Maddieson, 1990, for a review）.Similarly, the data suggest that the high front vowels in Ningbo contrast in three ways of lip rounding.But unlike the Swedish case,which distinguishes lip protrusion from lip compression （also known as ‘inrounded’）, Ningbo seems to distinguish in horizontal vs.vertical lip protrusion.
（2） Acoustical properties and the articulatory mechanisms of apical vowels are investigated.
（3） Acoustics and articulation of short vowels are discussed.
（4） Acoustical and aerodynamic aspects of nasal vowels and vowel nasalization are investigated and an attempt is made to quantify the nasality in terms of the aerodynamic measurements.
（5） Acoustics and articulation of diphthongs are investigated.Both static and kinematic aspects of diphthong production are interpreted in both acoustical and articulatory terms.