SPEECH

human communication through spoken language. Although many animals possess voices of various types and inflectional capabilities, human beings have learned to modulate their voices by articulating the laryngeal tones into audible oral speech. human communication through spoken language. Although many animals possess voices of various types and inflectional capabilities, human beings have learned to modulate their voices by articulating the laryngeal tones into audible oral speech. Most speech sounds are made with the pulmonary airstream (that is, air exhaled from the lungs) as it passes between the vocal cords at the base of the throat and out through the vocal tract (consisting of the pharynx, oral cavity, and nasal cavity). Speech sounds may be voiced or unvoiced. In making voiced sounds, the vocal cords are tensed so as to narrow the air passageway (glottis) between them; a cyclic series of changes in pressure of the air passing through the glottis is initiated by this original tension, vibrating the vocal cords and the air between them to produce sound. The frequency of these vibrations determines the pitch of the voice: for a bass voice, 75100 cycles per second is usual; for a soprano, more than 400 cycles per second. The airstream passing through the vocal tract is shaped into a series of syllabic, or segmented, speech sounds by the articulators: mainly the tongue, palate, and lips. Articulatory phonetics describes individual speech sounds in terms of whether they are voiced or unvoiced and in terms of the position and action of the articulators used in making them. For instance, the S sound in the English word sing is an unvoiced labial-alveolar fricativethat is, a friction sound made by air passing between the raised tongue and the alveolar ridge (upper gums) and lips (labia). Other types of consonants include stops, or plosives (where the oral airstream is closed off and then released, as with the sounds for T and D), approximants (where the airstream is almost closed off but friction is not produced, as with the W sound in weep), trills (where an articulator is vibrated, as in the Spanish R sound), or laterals (where the airstream moves along the edges of the tongue, rather than through the centre of the vocal tract, as with the sound for the double L in pullet). Vowels are produced with the vocal tract unobstructed and are traditionally specified in terms of which part of the tongue is raised highest in articulation and how high it is raised; thus, the sound for the double E in English keep is a high front vowel, that for the O in shoe a low (or open) back vowel. Speech is also described in terms of syntax (rules for putting words together to form phrases, clauses, or sentences), lexicon (meanings of words or of morphemes, the smallest meaningful segments of words [e.g., the prefix un-]), and phonology (sounds). Phonological rules specify which sounds are used in a language to distinguish one meaning from another; these sounds are called phonemes. For instance, English phonology carries /b/ and /p/ as distinct phonemes, since the substitution of one for the other will change the meaning of some utterances (as in bin and pin). American English has 13 or more distinct vowel phonemes. The phonological rules of a language also specify the alternate forms (allophones) of each phoneme and which allophone will be used in a given context. For instance, in English, the aspirated P and unaspirated P are allophones of the phoneme /p/, since it is the context of adjacent sounds, and not of meaning, that determines which is used; e.g., aspirated P occurs at the beginning of a word (park), unaspirated P occurs following S (spark). Thus, the lexicon of a language will consist of a list of combinations of phonemes, each combination representing the basic form of a word having a certain meaning. The phonological rules will yield the forms that each phoneme takes as it is combined with other phonemes to make the sentences allowed by the grammar. Additional reading V.E. Negus, The Comparative Anatomy and Physiology of the Larynx (1950), an excellent introduction to the understanding of function and evolution of the voice organ in man and animals; G. Fant, Acoustic Theory of Speech Production (1960), a modern, detailed exposition of acoustic phonetics, the science of the acoustic structure of speech sounds and their production; H. Fletcher, Speech and Hearing in Communication, 2nd ed. (1953), a classic work on the physiology of speech and hearing; P.B. Denes and E.N. Pinson, The Speech Chain (1963), highly recommended for high school and college level students. See also William M. Shearer, Illustrated Speech Anatomy (1979); Roderick P. Singh, Anatomy of Hearing and Speech (1980); Willard R. Zemlin, Speech and Hearing Science: Anatomy and Physiology (1981); and David Ross Dickson and Wilma Maue-Dickson, Anatomical and Physiological Bases of Speech (1982). See also recent issues of these journals: American Speech and Hearing Association (ASHA) Journal (monthly); Journal of Speech and Hearing Disorders (quarterly); and Journal of Speech and Hearing Research (quarterly).