Why do empty radio frequency make that sound instead of just being completely silent?

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Why do empty radio frequency make that sound instead of just being completely silent?

In: Technology
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* For analog radio equipment, it’s difficult to know when a signal is a legitimate broadcast or just background noise.
* Also, with analog radio broadcasts, a signal could be very faint and yet still have listenable qualities, so radios don’t blank out channels even if they detect mostly noise because the user might still want to listen.
* With digital broadcasts, there is identifying information in the broadcast data that tells the radio this is a station.
* Without that data, the radio knows it’s just background noise.

The universe is very noisy. The sun, every star, all the combined muck our electric and electronics produce, and even the remaining radio echoes from the big bang, make every part of the radio spectrum be full of noise.

When you have a channel broadcasting, the signal it broadcasts is louder than the noise, so the signal hides the noise.

When there is no signal, your radio turns up the volume in case there is something there. Eventually, the volume (this is called the AGC, if you want to search) is turned up until it is the noise that is loud.

It can also be CMBR, or Cosmic Microwave Background Radiation. It’s the residual noise from the Big Bang. It makes up about 10% of what we hear as static.