growl vs let out

growl is a noun but let out is not a noun.

Word	Noun	Adjective	Verb	Adverb
growl	Yes	No	Yes	No
let out	No	No	Yes	No

As verbs, let out is a hypernym of growl; that is, let out is a word with a broader meaning than growl:

Other hypernyms of growl include emit, let loose, utter.

growl (noun)	let out (noun)
the sound of growling (as made by animals)

growl (verb)	let out (verb)
to utter or emit low dull rumbling sounds	make (clothes) larger
	make known to the public information that was previously known only to a few people or that was meant to be kept a secret
	express audibly; utter sounds (not necessarily words)
	bring out of a specific state