Silence a boundary notion, a conceptual ideal, an aural vanishing point. Saying something about silence equals loosing it. Being silent is impossible may it include to cease living. Many words have been uttered to grasp this paradox.

There is no such thing as silence. Something is always happening that makes a sound.

No Silence exists, that is not pregnant with sound.

Until I die there will be sounds. And they will continue following my death. –  John Cage

Silence is a word which is not a word, and breath an object which is not an object. –  Georges Bataille

We should be sensitive to the thread of silence from which the tissue of speech is woven. –  Maurice Merleau-Ponty

Ther are two silences. One when no word is spoken. The other when perhaps a torrent of language is being employed. This speech is speaking of a language locked beneath it. That is the continual reference. The speech we hear is an indication of that we don’t hear. It is a necessary avoidance, a sly, anguished or mocking smokescreen which keeps the other in its place. –  Harold Pinter

Noise may have lost its power to offend. Silence hasn’t. –  Dan Warburton

The fear of silence is nothing new. Silence surrounds the dark world of death. Sometimes the silence of the vast universe hovers over us, enveloping us. There ist he intense silence of birth, the quiet silence of one’s return to the earth. Hasn’t art been the human creature’s rebellion against silence? Poetry and music were born when man first uttered sound, resisting the silence. –  Toru Takemitsu

When silence is conceived as the rejection of the human personality, the ulitmate silence is death. Then man likes to surround himself with sounds in order to nourish his fantasy of perpetual life. In Western society silence is negative, an embarrassment, a vacuum. Silence for Western man equals communication hangup. If one does not speak, the other will speak. –  R. Murray Schafer

The essence of sound is felt in both motion and silence, it passes from existent to nonexistent. When there is no sound, it is said that there is no hearing, but that does not mean that hearing has lost its preparedness. Indeed, when there is no sound, hearing is most alert, and when there is sound the hearing nature is least developed. –  Kirpal Singh

But if it’s true that all symphonies end in silence, it’s equally true that they begin there as well. Silence, after all, both buries and births us, and just as life without the counterweight of mortality would mean nothing, so silence alone, by offering itself as the eternal Other, makes our music possible. –  Marc Slouka

Any given silence takes its identity as a stretch of time being perforated by sound. A genuine emptiness, a pure silence, are not feasible — either conceptually or in fact. If only because the art-work exists in a world furnished with many other things, the artist who creates silence or emptiness must produce something dialectical: a full void, an enriching emptiness, a resonating or eloquent silence. Silence remains, inescapably, a form of speech (in many instances, of complaint or indictment) and an element in a dialogue. –  Susan Sonntag

There is a beautiful page with lots of writings about silence. And please check the essay „The Aesthetics of Silence“ of Susan Sontag.