Whereas obstruents are frequently voiceless, sonorants are almost always voiced. A typical sonorant consonant inventory found in many languages comprises the following: two nasals, two semivowels, and two liquids. 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. 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 have 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 and in certain language families. One European language with voiceless sonorants is Welsh. Its phonology contains a phonemic voiceless alveolar trill, along with three voiceless nasals: velar, alveolar and labial. 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 regularallophone 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.
Examples
has the following sonorant consonantal phonemes:. Old Irish had one of the most complex sonorant systems recorded in linguistics, with 12 coronal sonorants alone. Coronallaterals, nasals, and rhotics had a fortis-lenis and a palatalization contrast:. There were also and, making 16 sonorant phonemes in total.
Sound changes
Voiceless sonorants have a strong tendency to either revoice or undergo fortition, for example to form a fricative like or. In connected, continuous speech in North American English, and are usually flapped to following sonorants, including vowels, when followed by a vowel or syllabic.
