Synonyms:
* Whispered: This implies a soft, quiet, and often secretive tone.
* Uttered: This is a more general term for speaking, but can also imply a soft or low voice.
* Muttered: This suggests a low, grumbling voice, often expressing dissatisfaction or annoyance.
* Hinted: This implies a subtle suggestion or implication.
* Said softly: This is a straightforward synonym, emphasizing the low volume.
Antonyms:
* Shouted: This is the opposite of whispering, signifying a loud and forceful voice.
* Boomed: This suggests a very loud and deep voice.
* Yelled: This implies a loud and angry outburst.
* Declared: This implies a formal and assertive announcement.
* Proclaimed: This suggests a loud and public statement.
The best synonym or antonym will depend on the specific context of your sentence.