SPEECH, the production of articulate sounds by the voice organs; it consists in tones of voice modified by the agency of the tongue, cheeks, lips and other structures intervening between the glottis and the outer opening of the mouth. The modifications of articulate sounds which may be invented and used by man are almost without limit; the modifica tions actually used in the ordinary speech of all mankind numbers at least a thousand, and a universal language would have to provide symbols representative of that many speech sounds. Nevertheless, the number of distinct sounds in any one language seldom exceeds 50. In English speech two classes of sounds are produced, known as vowels and consonants. Vowels are pronounced by sounds coming pri marily from the larynx; consonants are formed by sounds due to of the currents of air in the mouth or passages above the larynx. The name consonant denotes a sound that cannot be produced effectively without the aid of a vowel. The vowels are further dis tinguished by the fact that they can be sounded mutely, or in a whisper. The differences be
tween vowel sounds are owing to . differences in the dimensions of the space between tongue and palate (mouth cavity) and of the mouth opening, when the vowels are pronounced, as shown in the following table: Size of Size of mouth- mouth Vowel Sound opening cavity a as in far S 3 e as et in vein 4 i as in marine 3 2 o as in cold 2 4 • as co in moos 1 Vowels sounds can be prolonged indefi nitely; so may some consonants, as 1, m, n, r, s, z, etc.; but others as b, p, t, d, k, g hard, cannot be prolonged. Absence of the sense of hearing prevents the perception of sounds and also their imitation— hence persons born deaf are necessarily dumb, but through training such persons may acquire the power of speech. Where dumbness exists without deafness the affection is due to some disorder of the nerve centres. See LANGUAGE, SCIENCE OF; VOICE AND VOICE CULTURE.