White noise vs pink noise. Listen, then choose.

Why it works

White noise spreads its energy evenly across every frequency. Pink spreads it evenly across every octave, which means progressively less at the top. Since hearing works in octaves, pink sounds balanced and white sounds bright. Pink is the one most people describe as rain. White is the one they describe as a hiss.

Both are good at hiding a neighbour's television. Neither is good at hiding your own thoughts, which are not a sound. For those, something has to be said aloud, slowly, about a subject that asks nothing of you. That is the third thing this player does.

What you are hearing

• Soft white noise. True white noise, equal energy at every frequency, with the sharpest part above 4,000 Hz taken off so it is easier to live with.
• 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.