Bilateral audio

A single sound alternates between your ears in a steady left-right pattern, usually about once a second. Often it is a soft tone or a plucked note laid over ambient music.

Once you know to listen for it, the movement is unmistakable. Something travels across your head.

The trap worth knowing about

The alternating tones are often at slightly different pitches. One side a little higher than the other.

On paper that looks exactly like the recipe for a binaural beat: two tones, two pitches, one per ear. It is not, and the reason is the one thing binaural beats cannot do without. Those tones take turns. They never sound at the same moment, so no binaural beat is produced.

This is the single biggest source of confusion in this subject, and it is why a track can be built from two detuned tones and still not be binaural in any sense.

Headphones, again

The whole technique is the movement between your ears, so your ears have to be getting different things.

Speakers can carry left and right, but the movement goes shallow, and it only works if you sit still in exactly the right spot between a properly placed stereo pair. Headphones remove the uncertainty.

Does it work

The evidence for bilateral audio on its own is thinner than for binaural beats. Some people find it helps a great deal. That is worth saying plainly alongside the thinness of the evidence, because both are true.

You can hear one of these next to the other, which settles the distinction faster than any description.

If you want to know where this technique came from and what has actually been measured, the research page has all of it.