sound has 22 distinct synonyms spread across 12 of its 25 senses. Each sense below keeps its own list, because a synonym belongs to a meaning and not to a word: swapping one sense's substitute into another sense's sentence is how a thesaurus makes writing worse. Its 2 recorded opposites are unsound, silence.
Counts are distinct word forms across every sense. A synonym that appears under three senses is counted once here and shown three times below, under each sense it belongs to.
financially secure and safe
“sound investments”
exercising or showing good judgment
“healthy scepticism”
in good condition; free from defect or damage or decay
“a sound timber”
appear in a certain way
“This sounds interesting”
3 of the 25 recorded senses carry no synonym, antonym or related term, so they are not shown above. Every sense, with its definition and examples, is on the full entry for sound.
Synonyms, antonyms and the broader and narrower relations for sound come from Princeton University’s WordNet. Full sources and licences.
mechanical vibrations transmitted by an elastic medium
“falling trees make a sound in the forest even when no one is there to hear them”
the audible part of a transmitted signal
“they always raise the audio for commercials”
(phonetics) an individual sound unit of speech without concern as to whether or not it is a phoneme of some language
a narrow channel of the sea joining two larger bodies of water
a large ocean inlet or deep bay
“the main body of the sound ran parallel to the coast”
announce by means of a sound
“sound the alarm”