speak up vs sound off

speak up and sound off both are verbs.

Word	Noun	Adjective	Verb	Adverb
speak up	No	No	Yes	No
sound off	No	No	Yes	No

As verbs, speak up and sound off are synonyms defined as:

speak up and sound off: express one's opinion openly and without fear or hesitation

Other synonyms of speak up include animadvert, opine, speak out.

speak up (verb)	sound off (verb)
express one's opinion openly and without fear or hesitation	express complaints, discontent, displeasure, or unhappiness
speak louder; raise one's voice	express one's opinion openly and without fear or hesitation
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