'sound off' definitions:

Definition of 'sound off'

From: WordNet
verb
Express one's opinion openly and without fear or hesitation; "John spoke up at the meeting" [syn: opine, speak up, speak out, animadvert, sound off]
verb
Start playing; "The musicians struck up a tune" [syn: sound off, strike up]
verb
Express complaints, discontent, displeasure, or unhappiness; "My mother complains all day"; "She has a lot to kick about" [syn: complain, kick, plain, sound off, quetch, kvetch] [ant: cheer, cheer up, chirk up]