Lisping, stammering, and other kinds of imperfect speech, are mainly due to nervous disease, stammering being usually caused by temporary spasm of the glottis. Too high a palate is another cause of irregular utterance. Dumbness, when not occasioned by deafness, as is generally the case, must be ascribed either to malformation of the vocal organs, or, more commonly, to disease of the nervous centres. Whistling, it must be remembered, results from the vibration caused by the friction of the breath against the edges of the open lips, and is wholly formed in the mouth.
The mouth, or chamber of resonance, is especially important for the creation of articulate speech. On the one side there are a great many sounds which owe to it their origin, on the other side even the sounds which are formed in the throat are necessarily modified in passing through the mouth. While t, p, or k have no existence until the voiced breath has reached the region of the mouth, the vowels which are formed in the throat cannot be heard in their pure and original state, but must pass through a chamber of resonance and so become more or less transformed. The throat, again, may remain passive, but the mouth must always be active. Of course the mouth forms a chamber of resonance not only for the sounds produced by the throat, but also for those produced by itself; the larger part of the mouth, for instance, forms a chamber of resonance for the palatal ch. We must remember, moreover, that a sound can be more variously changed and modified, the larger and more variable is the part of the mouth which serves as a chamber of resonance, that is to say, the further back the place is in which it is manufactured. The vowels consequently come first in capability of modification, then the gutturals and dentals, and finally the labials. It has often been observed that children when learning to speak are apt to change a guttural into a dental, and say do instead of go, the guttural being formed further back than the dental, and so undergoing a greater amount of modification in its passage through the mouth.
A vowel is voice freely emitted through the throat and mouth without interruption, and modified only by the different positions assumed by the tongue. The essence of a vowel is the quality or timbre of the voiced breath, and this quality, as we have already seen, is due to the varying forms taken by the vibrating vocal chords when played upon by the breath. Necessarily, however, the quality of the voice as it leaves the throat must be always the same, since the throat is a musical instrument which possesses its own peculiar tone. What, then, is the cause of the differences we notice in the quality of the vowels? Simply the mobility of what we have called the chamber of resonance, the manifold shapes the organs of the mouth are able to assume being so many musical instruments, each with its peculiar tone. The partial tones or harmonics which go to make up the quality of the voiced breath are strengthened by the corresponding peculiar tones of the several shapes assumed by the mouth, while at the same time those harmonics which do not agree with the peculiar tones are dulled or deadened. Hence a vowel is the quality of voiced breath produced by a combination of the forms of the vibrations of the vocal chords with those of the vibrating air in the various shapes taken by the chamber of resonance. The pitch of the vowel depends of course on the number of vibrations during the time of utterance, and may be detected even when the vowel is whispered. Indeed, as Donders and Helmholtz have shown, every vowel has its characteristic pitch, whether it is voiced or whispered. The different vowels can be heard in cases of aphonia, where the vocal chords are more or less paralyzed, while the vox clandestina is able to rise or fall. This is explained by the fact that even in whispering a certain friction is exercised on the vocal chords. If, for instance, we whisper the sound of ü, and then let the whisper gradually pass into a whistle, we shall always get the same tone, and Professor Max Müller thinks that the indications of musical pitch in the whispered vowels must be treated as “imperfect tones; that is to say, as noises approaching to tones, or as irregular vibrations, nearly, yet not quite, changed into regular or isochronous vibrations.”[150]
The number of possible vowel-sounds is almost infinite. The vocal chamber of resonance is almost infinitely variable in the forms it may assume, and it is in these forms, as we have seen, that we must find the origin of the vowels and their nuances of sound. In Prince L.-L. Bonaparte’s alphabet, as given in Mr. A. J. Ellis’s “Early English Pronunciation,” seventy-five vowel-sounds (exclusive of ḷ and ṛ) are distinguished from one another, ten of which occur in no actual language, and of the remaining sixty-five, fifty occur each in less than nine European dialects. For practical purposes, however, it is necessary to analyze the formation of those vowels only which are heard most usually in spoken language, always remembering that the nuances of which these are capable are nearly unlimited, and that the same speaker is constantly varying what he intends and believes to be the same vowel-sound. Speaking generally, we may say that in pronouncing the vowels we invariably raise the tongue towards the palate, but not so as to touch it—as in the case of the consonants—the lips being passive in some instances, and rounded in others. It is needless to note that in phonology, as in all other departments of the science of language, the Italian pronunciation of the vowels must be adopted. Our erroneous pronunciation of the vowel-symbols is not one of the least important reasons for urging a reform of English spelling.
The three fundamental vowels, round which all the others group themselves, are a, i, and u; and though it is not necessary to hold that these were the first vowel-sounds articulated by man, it is necessary to regard them, for analytical purposes, as the primary elements to which the rest may be ultimately referred. According to Winteler, these three vowels must be arranged in a straight line, of which i forms one end and u the other, a standing in the middle.
In forming a the tongue is in a more constrained position than in the case of any other vowel; it lies flat and retracted, while the lips are wide open. Helmholtz makes its inherent tone B″ flat. Owing to the constrained position of the tongue, this vowel is more liable to be modified than any other; the “neutral” a is scarcely ever heard, produced as it is by the gradual narrowing of the movement of the tongue from the back of the mouth, where the obscure a of father is heard, to the front of the mouth, where we get the broad ä of pair. This neutral a which may be heard in the Italian ămātă is not the “natural” sound it is sometimes called; different parts of the mouth must be modified to create it, occasioning the nasal sound we perceive in moaning if the mouth remains passive, or the shrill ä of the new-born child, if the nasal orifice is closed by the elevation of the soft palate.[151] The belief that language was once in a stage in which the neutral a was the only vowel known is contradicted by the facts of phonology.
A stronger effort of articulation is required for i and u. The lips must be slightly opened, the larynx raised, and the tongue pushed upward, so that its front approaches the hard palate, if we want to produce i, the natural pitch of which is said to be D⁗. The movement of the tongue from the back to the front of the mouth, with a gradual narrowing of the air passage, forms both the i of mill, and the i of meal.[152] As we shall see, the position of the tongue in forming i approaches that required for forming the palatals, and thus explains the relationship that exists between them. For u the tongue is raised towards the soft palate, the larynx lowered, and the lips rounded; hence the connection between this vowel and the labials. Its connection with the gutturals, as illustrated by the change of werra into guerre, or vespa into guêpe, is explained by the position of the tongue, which approaches the soft palate in forming u, and touches it in forming k or g. The rounded shape of the mouth needed by u, as compared with its narrow neck-like appearance needed by i, strengthens the deep partial tones, and dulls the sharp ones, thus occasioning the converse effect of i. In fact, u is essentially the vowel of the bass, i of the soprano. The inherent tone of u is F.
It is obvious that an almost endless series of modifications may be made in the primary vowels by slight changes in the position of the organs by which they are produced. Between a and i stands e; between i and u, o. In pronouncing e the tongue is less raised than in pronouncing i; for o, the back of the tongue is less raised and the lips more widely opened than for u. In o, however, as in u, the lips have to come into play; hence it is that these two sounds are so frequently weakened to e and i, whereas the converse change never takes place. In e and i we have a simple and not a double action. According to Helmholtz, the inherent pitch of o is B′ flat, of e, B‴ flat or F′.
But e and o may again undergo considerable change. If while pronouncing close e (as in the French été or German see) we round the lips, the sound is produced which is represented by ö in Middle and Southern German and eu in French, the short sound of which may be heard in the German böcke. It lies, it will be observed, between e and o, and its inherent pitch is C‴ sharp. Closely related to this ö is the German ü, French u. This sound is produced by rounding the lips when the organs of speech are in position for pronouncing i, which explains the use of ü and i as rhyming equivalents in German poetry. Ü consequently lies between i and u, though, from another point of view, it may be described as standing furthest from a in a series of which ö forms the centre. The inherent pitch of ü is G‴.
Besides o, we have also the sound heard long in words like bought or aúgust, and short in words like not and augúst, formed by slightly depressing the tongue, widening the air-passage, and rounding the lips to a less extent than in the case of o.