Experimental Phonetics

Phonetics

Phonetics is the study of speech sounds, including the isolated speech sounds of vowels, diphthongs (combinations of two vowels), and consonants as well as their physiological production and acoustic features. Articulatory phonetics involves the various configurations (shapes) of the human vocal tract determined by the vocal folds of the larynx (“voice box”), pharynx (throat), oral cavity (mouth), nasal cavity (nose), and lips used to produce speech sounds. Acoustic phonetics involves the acoustic properties of speech sounds, whereas linguistic phonetics involves the mechanism for combining speech sounds to produce syllables, words, phrases, and sentences.

Phonemes are the individual sounds of a language. They include consonants, vowels, and diphthongs (combinations of two vowels). Consonants can be classified as voiced (example: /b/ and /d/) or voiceless (example: /p/ and /t/). All vowels are voiced (i.e., they involve vibration of the vocal folds of the larynx), the anatomical structure in the neck region below the trachea (windpipe) responsible for producing speech and other nonspeech sounds. Examples of English vowels include /i/ (as in bee), /e/ (as in case), /ε/ (as in net), /ae/ (as in bat), /u/ (as in soon), and //(as in saw). Diphthongs are combinations of two vowels. Examples are / I/ (as in noise), /eI/ (as in paid), and / a/ (as in now).

The traditional approach to describing speech sounds is based on the movements of the anatomical structures that produce them. These structures include the articulators (tongue, lips, teeth, alveolar [gum] ridge, hard palate, and soft palate), as well as the respiratory system (airstream from the lungs), and, for voiced sounds, the vocal folds of the larynx. The airstream from [Page 647]the lungs passes between the vocal folds, which are two small muscular folds located in the larynx at the top of the trachea. If the vocal folds are apart, as they are normally for vegetative (nonspeech) breathing, the air from the lungs will have a relatively free passage into the pharynx and the oral cavity. But if the vocal folds are modified to create a narrow passage between them, the airstream will cause them to be sucked together, with no flow of air, and the pressure below them will build up until they are blown apart. The flow of air between them will then cause them to be sucked together again, and the vibratory cycle will continue. Sounds produced when the vocal folds are vibrating are voiced sounds (all vowels, diphthongs, and voiced consonants); when the vocal folds are apart, they are voiceless sounds (all voiceless consonants).

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