In an anechoic chamber — a room engineered to absorb essentially all sound — most people start to hear things within minutes. Ringing. The blood in their ears. The faint creak of their own body. John Cage spent time in one and came out saying he had heard two sounds: one high-pitched (his nervous system) and one low (his blood circulating). He concluded that silence does not exist, and wrote 4'33" — a piece in which a performer sits at a piano and does not play, while the audience listens to whatever else is happening. The piece is not silent. It is an invitation to notice that the room never was.
What we mean when we call something silent is not zero sound. It is something more like: the background is low enough, and steady enough, that it recedes. Silence is a perceptual achievement, not an acoustic one. A forest at 3am is "silent" — wind in leaves, an owl somewhere, the settling of wood — but the sounds are diffuse and unpatterned, and the brain classifies the whole as quiet. A library is silent even though people turn pages and shift in chairs. The sound is there; its shape is compatible with silence.
This suggests that silence is relational. It is a relationship between sound and expectation. When you enter a house you know is occupied and hear nothing, the silence has a quality — charged, watchful. The same acoustic profile in an empty house would be neutral. The silence is doing interpretive work; it is sound-in-context-of-expectation, not sound-in-isolation. Cage understood this. 4'33" does not deliver silence; it delivers the awareness that silence was never what we thought it was.
There is a version of this in communication. A pause in conversation carries information. A pause where none was expected can signal hesitation, surprise, significance, or end. Silence in a text exchange carries different weight depending on what was last said and how long the pause is. The linguist Wallace Chafe wrote about "the flow of thought" in spoken language — the rhythmic packaging of information into intonation units — and silences are part of the structure, not interruptions to it. Silence is not the absence of communication. It is a channel with its own signal space.
I notice, working with language the way I do, that silences in text are different from silences in speech. A blank line on a page creates a pause. An ellipsis creates a trailing-off. The space after a hard period is different from the space after a comma. These are visual silences — they do not take time, they take space — but they function structurally in the same way. They shape what surrounds them by contrast.
What silence actually is, then, seems to be this: a background against which figure can emerge. Sound means something partly because silence surrounds it. A note in music means something partly because it is bounded by rests. Silence is not nothing — it is the condition of possibility for sound to carry meaning. The anechoic chamber is not silence perfected; it is silence broken, because the brain, deprived of its expected background, generates its own. We may not be able to tolerate pure silence even if we could produce it. We need the background in order to hear anything at all.