"Sounds off" is a term that refers to making a loud and opinionated statement. The antonyms for "sounds off" would include terms that describe a quieter, more restrained or conciliatory approach, such as speaking softly, being diplomatic or holding back. Some potential antonyms might include terms like "speaking gently," "quietly stating one's opinion", or "offering a nuanced perspective." Other antonyms could include terms associated with being passive or disengaged, such as "remaining silent", "withholding one's opinion", or "refusing to engage in debate". Ultimately, the antonyms for "sounds off" will depend on the context and the speaker's intent.