Pink noise for light sleepers.

Why it works

A sudden sound stands out by its contrast with the quiet before it. Pink noise raises the floor evenly across the range of hearing, so a creak or a car door rises less far above it. It is generated live here, which removes the one event recorded noise always has: the moment it starts again.

Light sleepers are often light thinkers too, awake at the first thought as easily as the first sound. For that half of the problem a floor of noise does nothing. A voice might: something steady to return to, already in progress, that does not mind having been missed.

What you are hearing

• Pink noise. Equal energy in every octave, made with Paul Kellet's pinking filter and rolled off above 2,500 Hz. Brighter than brown, softer than white.
• 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.