speechsound

Speech sound is a basic unit of spoken language, realized by the vocal tract and used to distinguish words. In phonetics, a speech sound can refer to a phone—the concrete acoustic realization of a segment. In phonology, the analogous unit is the phoneme, an abstract segment whose differences can change meaning in a language. A language’s phonology thus consists of its inventory of phonemes and the rules governing their distribution and allophonic variation.

Speech sounds are typically divided into vowels and consonants. Vowels are produced with a relatively open vocal tract and are shaped by tongue height and backness, along with lip rounding, producing characteristic resonances known as formants. Consonants involve constriction or closure at one or more places in the vocal tract and are described by voicing, place of articulation (for example labial, dental, alveolar, velar), and manner of articulation (such as plosive, fricative, nasal, or approximant).

A key concept in phonology is that of allophones: context-dependent realizations of a phoneme that do not change meaning. For example, aspirated versus unaspirated stops can be allophonic in some languages, while in others they contrast phonetically meaningful phonemes.

Speech sounds vary acoustically and perceptually. Vowels are characterized by their formant frequencies, while consonants show patterns of noise or transient release in their spectra. The International Phonetic Alphabet provides a universal set of symbols to transcribe speech sounds across languages.

Studies of speech sounds span phonetics (production and perception), phonology (systematic organization), and clinical domains such as speech-language pathology.