Reality is flowing. This does not mean that everything moves, changes, becomes. Science and common experience tell us that. It means that movement, change, becoming is everything that there is. There is nothing else; everything is movement, is change. The time that we ordinarily think about is not real time, but a picture of space.
— Henri-Louis Bergson [via]
There is one thing that never changes—silence. Silence never changes, never flows, never moves. Silence just is. Silence is the reality that allows flow.
Silence never changes. Only the connotation, your attitude to it, changes depending on the sound or noise you hear before or after the silence, giving you, as Bergson says above, a “picture of space”, or to mix metaphors, an image of sound. The nothingness of silence remains nothing independent of the sound flowing through the the silence.
Silence can be a metaphor for the foundation of existence or being-itself. Silence, which is no-thing, allows sounds and noise to be, to exist as things to change and move. Silence gives a sound its very existence by marking the beginning and end of a sound. Silence gives a sound space and freedom to move and change, to mix with other sounds, to become. But in order for silence to do this, it must not change.
Maybe this is stretching the metaphor too far (I apologize if it breaks), silence is unknown. It is unknown because it is no-thing. Silence also exists on a level of non-duality with sound where there is neither subject nor object. On the surface, this sounds impossible (sorry, pun intended) because it appears that sound displaces silence—either you hear sound or you hear silence. But it is not either/or, it is both/and.
It is nearly impossible to hear or even imagine silence co-existing in the same moment with a sound, but it is there. If you quiet yourself and listen deeply to a sound (it is easiest with music, especially with headphones), there is an underlying stillness along with, under, about, the movement of sounds. Stillness is part of silence.
The very physics of sound carries silence with its very being among the troughs and crests of its sine wave. As the nothingness of space surrounds and permeates all matter, even atoms and subatomic particles, silence surrounds and permeates sound. But unlike space, which can be bent by gravitation, silence never changes. Silence even surrounds and permeates space itself.
Silence just is. It allows sound to be and to do what sound does, to move, to flow, to live. That is what silence does. For silence, be-ing and do-ing are the same.