The wind in the trees outside, the rain lashing against the window.
The low buzz/rumble of the kitchen extractor fan resonating slightly, varying up and down in pitch.
The gentle airy whirr of the laptop hard disk, with the odd click as it talks to itself.
The reliable tick...tick...tick...tick... of a small clock.
The 'tock' of a relay and the hum of a pump as the boiler preheats the heat exchanger.
What do you hear right now?