Vowel features

VOWEL FEATURES Mona Lindau University ofIbadan This paper presents an inventory ofthe features that are necessary to describe vowel systems in the languages of the world. The relationship between the features and their articulatory and acoustic correlates is explored. Some vowel features, like High and Back, are accounted for in both articulatory and acoustic terms. Others, like Peripheral, are best described with reference to the acoustic domain. When the number of contrasts of each feature is considered, some features turn out to be multivalued. This paper is an attempt to provide a first approximation to a set of features to specify contrasts and phonological processes involving vowels. The proposed set is exhaustive for these purposes. Most of the features have been proposed elsewhere, in particular by Ladefoged 1971, 1975; the major discussion here centers around the physical correlates of each. The number ofphonological values needed for each feature is specified. Features involving interactions between consonants and vowels have usually not been considered, because this would entail a discussion of consonant features which is outside the scope of this paper (concerning these, see Williamson 1977). The most basic vowel parameter is vowel height: all languages contrast high and low vowels. Another basic contrast is that between front and back vowels. Vowel height and backness form the foundation of a two-dimensional vowel space that is required to describe nearly all the languages of the world. Additional contrasts, like variations in lip position, pharyngal size, nasality etc. can be considered as superimposed on this basic vowel space. 1. High and Back. From the time of Bell 1867, the basic two-dimensional vowel space has been described in terms of the highest point of the tongue. Very often vowels are represented on a chart, as in the cardinal-vowel system (Jones 1917). In practice, the points on a vowel chart represent an auditory description in terms of how different the vowels of a particular language sound from certain reference vowels. However, most phoneticians using the cardinal-vowel system for describing vowels also claim that points on the vowel quadrilateral represent the position of the highest point of the tongue (e.g. Jones 1956, Abercrombie 1967, O'Connor 1973). This amounts to suggesting that we hear differences between vowels in a way that is directly related to how the highest point ofthe tongue moves in producing these vowels; and a specific claim to this effect has been made by Catford 1977. There is, however, very little evidence in support of this view, other than subjective muscular sensations. Using radiographic data from one speaker of Ngwe, Ladefoged 1964 concluded that the highest point of the tongue was not a good representation of vowel height and backness, particularly for the back vowels. He argued instead that these features were more closely related to their acoustic properties on a formant chart. Following Joos 1948, he equated vowel height with the inverse of the frequency of the first formant. (High vowels have a low first formant, low vowels a high first formant.) Later, Ladefoged suggested (1975) that position on the front-back 541 542 LANGUAGE, VOLUME 54, NUMBER 3 (1978) dimension was best equated with the difference between the frequencies of the first and second formants. The back vowels are in better correspondence with the way in which they are heard when one relates backness to the difference between the first and second formant frequencies, rather than to the second formant frequency alone. On the usual acoustic chart, in which the first formant frequency is plotted against the second formant frequency, the vowels form a triangle where the high back [u] is further back than [o]. A chart with F2-F1 plotted against F1 looks more like the cardinal-vowel chart : the back vowels fall on a slope, with [u] slightly more forward than [d]. Ladefoged (ms) illustrates the close relationship between the auditory and acoustic properties of vowels by comparing Danish vowels as plotted on a cardinal-vowel chart (H. J. Uldall 1933) with the formant frequencies of Danish vowels plotted on an acoustic chart (Fischer-J0rgensen 1972). These two charts are reproduced here as Figure 1. The formant chart is clearly a good description of these...