Can someone tell me what really is the sound of silence?

Silence is the absence of sound, technically not a definition because most ontologies do not allow for the inclusion of 'things that aren't'. A confusing answer. I don't know if you can ever truly hear silence. The closest you can get is to remove the world- all outside sounds - and you're left with just you, and you would be able to hear your blood pumping - you may not recognize it, but you would technically be able to hear it.

The sound of silence refers to the state of mind a person is in when they meditate and are focused enough that they do not (hear) any outside noises, nor do they have any inner noise.

no one on the beach and the oceans ebb and flow that is silence to me and part of Heaven.

The sound of one hand clapping.

I actually hearing ringing or various tones.

Didn't you already ask this or was it someone else...?

It is a Simon and Garfunkle song.

The ringing in your ears.

Your own heart beat.

When you're waiting for the bill.

It's when nothing seems to be happening.