Onomatopoeia is the forming and use of words and phrases to imitate or suggest the sounds they describe, such as bang, whisper, cuckoo, splash and fizz. Onomatopoeia is one of the resources of language more often used by poets than prose writers; this is because poetry is made for the ear as well as the eye, and depends more heavily than prose does on sound-effects. Spike Milligan's 'On the Ning Nang Nong' makes heavy use of onomatopoeia, but it can play a role in classic poetry too - an example is the use of "Crash'd" to describe the noise of battle in Tennyson's 'The Charge of the Heavy Brigade'.

The 'Bats' Ultrasound' in Les Murray's poem of that title is represented, through onomatopoeia, as ü, in a stanza where all the words are chosen for their consonance with each other, and with bat-cries.