Whereas
obstruents are frequently
voiceless, sonorants are almost always voiced. In the
sonority hierarchy, all sounds higher than
fricatives are sonorants. They can therefore form the
nucleus of a
syllable in languages that place that distinction at that level of sonority; see
Syllable for details. Sonorants contrast with
obstruents, which do stop or cause turbulence in the airflow. The latter group includes
fricatives and
stops (for example, and ). Among consonants pronounced in the back of the mouth or in the throat, the distinction between an
approximant and a voiced fricative is so blurred that no language is known to contrast them. Thus,
uvular,
pharyngeal, and
glottal fricatives never contrast with approximants.
Voiceless Voiceless sonorants are rare; they occur as
phonemes in only about 5% of the world's languages. They tend to be extremely quiet and difficult to recognise, even for those people whose language has them. In every case of a voiceless sonorant occurring, there is a contrasting voiced sonorant. In other words, whenever a language contains a phoneme such as , it also contains a corresponding voiced phoneme such as . Voiceless sonorants are most common around the
Pacific Ocean (in
Oceania,
East Asia, and
North and
South America) and in certain language families (such as
Austronesian,
Sino-Tibetan,
Na-Dene and
Eskimo–Aleut). One European language with voiceless sonorants is
Welsh. Its
phonology contains a phonemic
voiceless alveolar trill , along with three voiceless nasals: bilabial, alveolar, and velar . Another European language with voiceless sonorants is
Icelandic, with for the corresponding voiced sonorants . Voiceless and possibly are hypothesized to have occurred in various dialects of
Ancient Greek. The
Attic dialect of the
Classical period likely had as the regular allophone of at the beginning of words and possibly when it was doubled inside words. Hence, many
English words from Ancient Greek roots have
rh initially and
rrh medially:
rhetoric,
diarrhea. Voiceless vowels are allophonic in many languages, particularly when surrounding voiceless consonants, but their phonological status as contrastive phonemes lacks strong evidence; cases where they were previously reported to have contrastive status have failed corroboration in later studies.
Glottalic Most sonorants have
glottalized variants. In languages that use
Latin scripts, they are often written with a modifier apostrophe, either preceding , succeeding , or above . Numerous studies have shown that the timing of glottalization for sonorants is fluid, and that they may be realized with: •
preglottalization (glottal onset), such as ; •
postglottalization (glottal offset), such as ; •
laryngealization (creaky voice) for the duration of the sounds, such as ; • or a combination of the aforementioned possibilities. For simplicity, the remainder of this section will transcribe these sounds with a preceding superscript glottal stop, as in , but these transcriptions should not be assumed to be phonetically precise in describing the type of glottalization; they are merely representative. It has been noted that
glottal stops with
palatalization and
labialization, respectively and , are quite similar to the glottalized sonorants and , and either case may be analyzed instead as sequences, and ; the specific interpretation of these sounds is mostly dependent upon how they pattern with other sounds within a particular language's phonological structure. Some languages (such as
Lillooet) may still contrast glottalized sonorants with glottal–sonorant or sonorant–glottal sequences. Glottalized vowels occur in a variety of languages and are perhaps the most common examples of glottalized sonorants. For consonants, the most common examples cross-linguistically of glottalized sonorants are the aforementioned palatal and labiovelar semivowels and , the alveolar lateral , and the bilabial and alveolar nasals and . Among others, they are particularly common in the
Salish,
Tsimshianic, and
Wakashan language families of the
Pacific Northwest, as well as several languages of the
Atlantic–Congo family of
Sub-Saharan Africa and the
Kra–Dai family of
mainland Southeast Asia and
southern China. Of the rarer glottalized sonorant consonants: •
Jingpo,
Khmu,
Kuyubí, and
Mangbai have a palatal nasal •
Chemehuevi,
Deg Xinag,
Hagei, Jingpo,
Lummi, Khmu,
Wui, and
Yapese have a velar nasal •
Lekwungen,
Klallam,
Saanich and
Samish have a post-velar or uvular nasal • Lillooet,
Shuswap, and
Coast Tsimshian have a non-labial velar approximant •
Coeur d'Alene, Lillooet,
Okanagan, Shuswap,
Spokane, and
Thompson have both plain and labialized pharyngeal approximants • Spokane and
Yurok have an alveolar approximant • Jingpo has a retroflex approximant ==Examples==