Question

"Ball goes in (thwack) to mitt,/ and goes out (thwack) back to mitt." This is an example of which sound device?

Answer 1

While there are many different sound devices that can be used in poetry, such as near rhyme (sounds are similar but not exact), alliteration (same beginning sounds), this one is onomatopoeia.  Onomatopoeia is using words to suggest a sound.  This can also be words like whispering, sizzle, thump, clang, etc.  Using onomatopoeia allows you to imagine what it would sound like if you were present (this is part of imagery).