Sound devices, also known as musical devices, are elements of literature and poetry that emphasise sound. The most common sound devices are assonance, consonance, alliteration, rhyme and onomatopoeia.
Assonance is the repetition of vowel sounds in nearby words. The following stanza from Poe's "Eldorado" contains an example of assonance:
But he grew old-
This knight so bold-
And o'er his heart a shadow
Fell as he found
No spot of ground
That looked like Eldorado.
Example of assonance: Eldorado, shadow, old, over, bold, no. There is the repetition of the "o" sound.
Consonance is the repetition of consonant sounds at the end or in the middle of words.
The following stanza from Lord Alfred Tennyson's "The Eagle" contains consonance. It is labelled after each line here:
He clasps the crag with crooked hands (the repetition of the "c" sound)
Close to the sun in lonely lands (repetition of the "l" sound)
Ringed with the azure world he stands (the repetition of the "r" sound)
Alliteration is the repetition of the initial consonant sounds in nearby words. The purpose of alliteration is to draw attention to specific words.
The first line of Poe's "The Raven" contains alliteration:
"Once upon a midnight dreary while I pondered weak and weary."
In this line, there is the repetition of the "w" sound in the words "while," "weak" and "weary."
Rhyme is the repetition of the same sound at the end of a word. For example, the following words all end in the "at" sound: cat, bat, sat, fat.
Onomatopoeia is a word that imitates the sound it represents. For example, "meow" sounds like the noise a cat makes. "Ring" is the sound produced by a telephone. "Woof" is the sound produced by a dog.