What is the part of speech that describes sound?

There isn't a specific part of speech that describes sound. However, we can use different parts of speech to describe or represent sound:

* Nouns: Words that name a sound, like "thunder, whisper, sizzle, boom, chirp".

* Verbs: Words that describe the act of making a sound, like "roar, hiss, crackle, buzz, twitter".

* Adjectives: Words that describe the quality of a sound, like "loud, soft, sharp, raspy, melodic".

* Onomatopoeia: Words that imitate the sound they describe, like "buzz, bang, meow, whoosh, tick-tock".

Ultimately, the specific part of speech used will depend on the context and what aspect of sound you're trying to express.