A warm fan hum that never loops.

Why it works

A fan is two sounds: air being pushed, which is broad and low, and a motor, which hums at the mains frequency and its double. This page builds both, from brown noise closed down at 240 Hz and two faint tones beneath it. Recorded fans give themselves away at the splice. This one has no splice.

People who sleep with a fan often want it for what it hides. It hides the house well and does nothing about the commentary. If yours is a commentary sort of night, bring the voice up a little. It is slower than your thoughts, and on a good night they fall into step with it.

What you are hearing

• Warm fan hum. Brown noise low-passed at 240 Hz for the moving air, with two faint tones at 60 and 120 Hz underneath for the motor.
• The voice. The first four minutes of Aristotle, the Greatest Philosopher, a Lullable story, in a synthesised voice. It only plays if you bring it in.
• The ending. The preview lasts four minutes. Its last ten seconds are a straight fade to silence, so it never stops abruptly.

For a real recording that runs forty minutes, the Lullable iPhone app has rain, waves, a campfire and plain noise, with no voice and no music.