Sleep sounds without a loop.

Why it works

Most sleep sounds online are short recordings set to repeat. Even a careful crossfade leaves something behind: the same gust, the same drip, the same faint rise every ninety seconds. The sounds here are different in kind. They are random numbers passed through a filter while you listen, and they have no second time around.

A loop bothers some people and not others. If you are one of the people who notices, you probably also notice your own thoughts coming round, the same three in the same order. A generator will not help with that loop. A story with a beginning, a middle and an end might.

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.