as a noun, 'sound' primarily refers to vibrations that travel through the air or another medium and can be heard when they reach a person's or animal's ear.
The sound of the rain is soothing.
Turn up the sound; I can't hear the movie.
The ferry crosses the Puget Sound to get to the island.
don't confuse the auditory 'sound' with the geographical 'sound' (like Long Island Sound).
as an adjective, 'sound' describes something that is in good condition, reliable, or valid. 'Sound' can describe reasoning, judgment, sleep, health, etc.
Her logic is sound.
He's in sound health.
She slept a sound sleep.
don't confuse the adjective form with other meanings of 'sound.' Context usually helps in distinguishing.
as a verb, 'sound' means to convey a certain impression when heard or to make a noise. 'Sound' can also mean to measure the depth of water, typically using a line or pole.
The alarm sounded at noon.
The phrase 'sounds good' is often used in agreement.
They sounded the depths of the lake.
'sound out' is a phrasal verb that means to try to ascertain someone's opinions, ideas, or feelings by talking to them.
as an adverb, 'sound' is used to emphasize that someone is in a particular condition or situation to a thorough or extreme degree. It's often used in the phrase 'sound asleep,' meaning deeply asleep.
The baby is sound asleep in her crib.
the adverbial use of 'sound' is less common than its other forms, and it's primarily found in the phrase 'sound asleep.'