Here's why:
* It describes a noun: We use it to describe something that is loud and harsh, like "a raucous party" or "a raucous laugh."
* It can be used as a noun: Although less common, "raucous" can sometimes be used as a noun to refer to the sound itself. For example, "The band's music was full of raucous."
It's important to note that "raucous" is not an adverb. Adverbs modify verbs, adjectives, or other adverbs, but "raucous" doesn't function in that way.