sound off vs declare

sound off and declare both are verbs.

Word	Noun	Adjective	Verb	Adverb
sound off	No	No	Yes	No
declare	No	No	Yes	No

As verbs, declare is a hypernym of sound off; that is, declare is a word with a broader meaning than sound off:

sound off (verb)	declare (verb)
express complaints, discontent, displeasure, or unhappiness	state emphatically and authoritatively
express one's opinion openly and without fear or hesitation	state firmly
start playing	make a declaration (of dutiable goods) to a customs official
	declare to be
	announce publicly or officially
	proclaim one's support, sympathy, or opinion for or against
	designate (a trump suit or no-trump) with the final bid of a hand
	authorize payments of