Binaural beats: what they are and what the evidence actually says

Binaural beats are easy to make, pleasant to listen to, and surrounded by claims that outrun the evidence. This page explains the effect itself, what the Greek letters mean, what research has and has not shown, and how to try it without hurting your ears.

What you are hearing

Play a 200 Hz tone into your left ear and a 210 Hz tone into your right. Neither ear hears anything unusual. But the brainstem compares the timing of signals from the two ears, which is how you work out where a sound is coming from, and that comparison produces a slow pulsing at the difference, 10 times a second.

That pulse is the binaural beat. It is not in the air and a microphone cannot record it. It is a perception created inside the auditory system.

Two consequences follow:

• Headphones are required. Through speakers the two tones mix in the room and you hear an ordinary acoustic beat instead. That is a monaural beat, a real physical wobble in loudness, and it is a different phenomenon.
• It only works in a narrow range. The effect is clearest with carrier tones below about 1000 Hz and differences below about 30 Hz. Push the difference higher and the pulse dissolves into two notes.

The Greek letters

Beat frequencies are usually labelled with EEG band names, because the idea is that the beat might nudge brain rhythms towards its own rate:

Band	Beat frequency	The brain rhythm it is named after
Delta	0.5 to 4 Hz	Deep, dreamless sleep
Theta	4 to 8 Hz	Drowsiness, light sleep, deep meditation
Alpha	8 to 12 Hz	Relaxed, eyes closed, awake
Beta	12 to 30 Hz	Alert, thinking, focused
Gamma	30 Hz and up	Attention, binding perceptions together

The bands are real and well documented. They describe what an EEG shows when a person is already in that state. The leap is the claim that hearing a 6 Hz beat puts you into a theta state. That is the entrainment hypothesis, and it is where the evidence gets thin.

What the studies show

Reading across the research rather than any single paper:

• People often report feeling calmer or more focused. Pooled analyses of controlled studies find a small to moderate effect on anxiety, attention and memory tasks. That is the strongest part of the record.
• The EEG evidence is mixed. Some studies detect a small signal at the beat frequency. Many careful ones find no change in brain rhythms at all, including in the band the beat was supposed to drive.
• The control condition matters. Sitting still for twenty minutes with headphones on and nothing to do is itself relaxing. Studies that compare beats against a plain tone or music at the same volume find much smaller differences than studies that compare against doing nothing.
• Dose and frequency are all over the place. Five minutes to an hour, carriers from 100 to 500 Hz, beats from 1 to 40 Hz. Nobody has shown that one setting reliably beats another.

A fair summary: binaural beats are a mild, pleasant, probably somewhat relaxing sound. The specific claims, this frequency for deep sleep, that one for learning, are not established. If they help you settle, that is a good enough reason to use them. It is not a reason to expect them to replace sleep, study or treatment.

How to try it

1. Put on headphones. Earbuds are fine as long as each ear gets its own channel.
2. Set the volume low, below where you would listen to music. A steady pure tone feels quieter than it is, and the energy sits on one frequency.
3. Pick a carrier around 200 to 400 Hz and a beat that matches what you are after. Start with alpha, 10 Hz, which is the easiest to hear as a pulse.
4. Give it a couple of minutes. The beat is subtle at first.
5. Stop after 15 to 20 minutes, or sooner if you notice pressure or ringing in your ears.

Where a tone generator fits

A binaural beat is just two sine waves with an offset, so any tone generator with a separate frequency per channel can make one. Tone Generator has a Binaural mode with one slider for the pitch and a second for the gap between the ears, from 0.5 to 100 Hz, with the five bands as one-tap presets at 2, 6, 10, 20 and 40 Hz. There is an auto-stop timer for falling asleep to it, and the app keeps playing with the screen off.

What it does not have is programmes, voices or promises. It makes the sound. Whether the sound does what the labels suggest is, as above, still an open question.