Vowels

sounds of speech, as opposed to consonants. Combined in a syllable with consonants, vowels always form its peak, that is, they perform the function of the syllable-bearer. The source of sound in a vowel is the voice, which is formed in the larynx by the quasi-periodic vibrations of the vocal chords. The epiglottal cavities (pharynx, mouth, and nose), called the adapter, serve as a resonator system whose contour changes as a result of different positions of the movable articulatory organs. As a result of the volume and shape of the resonator system during the transmission across it of the air stream carrying the vocal vibrations, amplification of the formants, which also determine the nature of vowels, occurs in certain areas of the frequency spectrum.

From an acoustical point of view, vowels are characterized by the presence of a clear formant spectral structure and a relatively high total sound energy; from an articulatory point of view, they are characterized by the absence of noise-producing interference in the vocal tract and relatively low expiration intensity.

The physiological classification of vowels is constructed in relation to the corresponding position of the tongue and the lips; furthermore, the participation of the nasal resonator and the pharynx is also taken into consideration. Vowels are distinguished by zones according to the movement of the tongue through the oral cavity. Front vowels are formed when the tongue moves forward (Russian i and e), back vowels are formed when the tongue moves backward (Russian o and u), and central vowels are formed when the tongue is located in the central portion of the mouth (several vowels in the Turkic languages). In addition, there are mixed vowels, which are formed when the tongue is positioned along the entire oral cavity (Russian y). According to the degree to which the tongue is raised, vowels may be closed, or narrow, if they are formed when the tongue is relatively high, and they may be open, or broad, if the tongue is in a relatively low position during their pronunciation. Vowels of the type of the Russian i and u are classified among the vowels with the greatest height; the vowel of the type of the Russian a is classified among the lowest vowels. Vowels of other types are located at different heights between these two extremes.

Vowels are also differentiated according to the position of the lips (or according to the shape of the lip opening). Labial (labialized, or rounded) vowels, as in Russian o and u, are pronounced with the lips rounded and pushed forward to varying degrees; and nonlabialized, or unrounded, vowels are pronounced without any such positioning of the lips, as in the Russian a, e, and i. Nasal (or nasalized) vowels—for example, in French—are produced by the inclusion of the nasal resonator by means of lowering the velum palatinum; nonnasal vowels are pronounced with the velum palatinum in the raised position. Constriction of the pharynx results in the pharyngealization of vowels, a phenomenon that is widely utilized in Arabic.

In the binary classification of the American linguist R. Jakobson and others, vowels are distinguished according to distinctive features, as follows: compact vowels, in which the first formant is located closer to the second and third formants, and diffuse vowels, in which it is further removed from the remaining formants; low vowels, in which the second formant is located nearer to the first, and high vowels, if it is nearer to the third; sharp vowels, which are characterized by a rising of the second and higher formants, and unmarked vowels, which do not have this increase; flat vowels, in which all formants shift downward, and unmarked vowels, which do not have this feature; and tense vowels, which differ from lax vowels by a greater deviation of the formants from a neutral position.

The zone and height of vowels are correlated with their acoustical characteristics in the fact that the second formant is raised during the pronunciation of front vowels, and the first formant is lowered when the height is increased.