A trill is a sound characterized by the rapid beating of one articulator against another. Although English has no examples, one is readily available in Spanish. The rolled r is in fact an alveolar trill, wherein the tension in the tongue is just right that when air passes over it, it triggers the bernoulli effect and the tongue begins to vibrate. The same alveolar trill [r] is found in Scottish Gaelic.
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- Crystal, David (1999) The Penguin Dictionary of Language. London: Penguin.
- Ladefoged, D. (2010) A Course in Phonetics. 6th Edition. Wadsworth Publishing.