croak vs let out

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

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

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

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

croak (noun)	let out (noun)
a harsh hoarse utterance (as of a frog)

croak (verb)	let out (verb)
pass from physical life and lose all bodily attributes and functions necessary to sustain life	make (clothes) larger
make complaining remarks or noises under one's breath	make known to the public information that was previously known only to a few people or that was meant to be kept a secret
utter a hoarse sound, like a raven	express audibly; utter sounds (not necessarily words)
	bring out of a specific state