Sonorants are those articulations in which there is only a partial closure or an unimpeded oral or nasal scape of air; such articulations, typically voiced, and frequently frictionless, without noise component, may share many phonetic characteristics with vowels.
The word resonant is sometimes used for these non-turbulent sounds. In this case, the word sonorant may be restricted to non-vocoid resonants; that is, all of the above except vowels and semivowels. However, this usage is becoming dated.
Sonorants contrast with obstruents, which do cause turbulence in the vocal tract. Among consonants pronounced far back in the throat (uvulars, pharyngeals) the distinction between an approximant and a voiced fricative is so blurred that such sounds as voiced uvular fricative ([ʁ]) and voiced pharyngeal fricative ([ʕ]) often behave like sonorants. The pharyngeal consonant is also a semivowel corresponding to the vowel [ɑ].
Whereas most obstruents are voiceless, the great majority of sonorants are voiced. It is certainly possible to make voiceless sonorants, but sonorants that are unvoiced occur in only about 5 percent of the world's languages. These are almost exclusively found in the area around the Pacific Ocean from New Caledonia clockwise to South America and belong to a number of language families, among them Austronesian, Sino-Tibetan, Na-Dene and Eskimo-Aleut. It is notable that, in every case where a voiceless sonorant does occur, there is a contrasting voiced sonorant.
Voiceless sonorants tend to be extremely quiet and very difficult to recognise even for those people whose language does contain them. They have a strong tendency to either revoice or undergo fortition to form for example a fricative like ç or ɬ.