In phonetics, a trill is a consonantal sound produced by vibrations between the active articulator and passive articulator. Standard Spanish <rr> as in label=none, for example is an alveolar trill. A trill is made by the articulator being held in place and the airstream causing it to vibrate. Usually a trill vibrates for 2–3 contacts, but may be up to 5, or even more if geminate. However, trills may also be produced with only one contact. While single-contact trills are similar to taps and flaps, a tap or flap differs from a trill in that it is made by a muscular contraction rather than airstream.
The bilabial trill is uncommon. The coronal trill is most frequently alveolar, but dental and postalveolar articulations and also occur. An alleged retroflex trill found in Toda has been transcribed , but might be less ambiguously written, as only the onset is retroflex, with the actual trill being alveolar. The epiglottal trills are identified by the IPA as fricatives, with the trilling assumed to be allophonic. However, analyzing the sounds as trills may be more economical. There are also so-called strident vowels which are accompanied by epiglottal trill. The cells in the IPA chart for the velar, pharyngeal, and glottalplaces of articulation are shaded as impossible. The glottis quite readily vibrates, but this occurs as the phonation of vowels and consonants, not as a consonant of its own. Dorso-palatal and velar vibratory motions of the tongue are occasionally produced, especially during the release of dorsal stops, and ingressive [|velar trills] occur in snoring, but not in normal speech. The upper pharyngeal tract cannot reliably produce a trill, but the epiglottis does, and epiglottal trills are pharyngeal in the broad sense. A partially devoiced pre-uvular fricative trill has been reported to occur as codaallophone of in Limburgish dialects of Maastricht and Weert. It is in free variation with partially devoiced uvular fricative trill. Voiceless trills occur phonemically in e.g. Welsh and Icelandic. Mangbetu and Ninde have phonemically voiceless bilabial trills. The Czech language has two contrastive alveolar trills, one a fricative trill. In the fricative trill the tongue is raised, so that there is audible frication during the trill, sounding a little like a simultaneous and . A symbol for this sound,, has been dropped from the IPA, and it is now generally transcribed as a raised r,. Liangshan Yi has two "buzzed" or fricative vowels which may also be trilled,. A number of languages have trilled affricates such as and. The Chapakuran language Wariʼ and the Muran languagePirahã have a very unusual trilled phoneme, a voiceless bilabially post-trilled dental stop,. A nasal trill has been described from some dialects of Romanian, and is posited as an intermediate historical step in rhotacism. However, the phonetic variation of the sound is considerable, and it is not clear how frequently it is actually trilled.
Extralinguistic trills
A linguolabial trill is not known to be used phonemically, but occurs when blowing a raspberry. Snoring typically consists of vibration of the uvula and the soft palate, which may be described as an ingressive velic trill. Like the uvular trill, the ingressive velic trill does not involve the tongue; it is the velum that passively vibrates in the airstream. The Speculative Grammarian has proposed a jocular symbol for this sound, a double-wide with double dot suggesting a pig's snout. The Extensions to the IPA identifies an egressive fricative pronounced with this same configuration, common with a cleft palate, as velopharyngeal, and with accompanying uvular trill as or. Lateral trills are also possible. They may be pronounced by initiating or with an especially forceful airflow. There is no symbol for them in the IPA. Lateral coronal trills are sometimes used to imitate bird calls, and are a component of Donald Duck talk. A labiodental trill,, is most likely to be lateral, but laterality is not distinctive among labial sounds. Ejective trills are not known from any language, despite being easy to produce. They may occur as mimesis of a cat's purr.
