Pink noise for sleep, made as you listen.

Why it works

Pink noise carries the same energy in each octave, which is roughly how the ear measures loudness. The result sounds balanced where white noise sounds sharp: steady rain, or wind in a great many leaves. Here it is produced by a small filter running in your browser, so there is no file and no place where it restarts.

It is an honest blanket for a noisy street. A blanket is not company, though, and some nights the noise is inside. Try the middle setting. A story told slowly enough needs very little attention, and the little it takes is attention your worries do not get.

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.