Put on headphones. In your left ear, a steady tone at 200 hertz. In your right, a tone at 210. You do not hear two notes. You hear one, with a soft pulsing ten times a second. That pulse is a binaural beat, and it exists only inside your head.
Millions of people listen to recordings built on this effect, sold with promises of sharper focus, deeper sleep and effortless meditation. Many hypnosis recordings include them. Do they do anything?
What a binaural beat is
The effect was described in 1839 by the Prussian physicist Heinrich Wilhelm Dove. When each ear receives a slightly different frequency, the brain’s hearing system, combining the two signals, produces the sensation of a beat at the difference between them.
It only works with headphones, with tones fairly low in pitch, and when the two frequencies are close together.
The claim
The marketing rests on an idea called brainwave entrainment.
The brain’s electrical activity has rhythms, loosely grouped into bands:
- Delta (about 1 to 4 per second): deep sleep
- Theta (4 to 8): drowsiness, light sleep
- Alpha (8 to 13): relaxed wakefulness
- Beta (13 to 30): alert concentration
- Gamma (above 30): intensive processing
The claim is that a binaural beat at, say, 6 per second will pull the brain’s own rhythm towards 6 per second, and so produce the relaxed state associated with theta. Choose your frequency, choose your state.
It is a neat theory. It has two parts that need checking: does the beat change brainwaves, and does it change how people feel or perform?
Does it change brainwaves?
A 2023 systematic review looked at 14 studies that had recorded brain activity during binaural beats to test the entrainment idea.
- Five reported results consistent with entrainment
- Eight reported results that contradicted it
- One was mixed
The authors found the outcomes inconsistent overall, noted large differences in how the studies were done, and urged caution about the claims.
So the mechanism the whole industry is built on is, at best, not established.
Does it change how people feel or perform?
Here the picture is more favourable, if still uncertain.
A meta-analysis published in 2019 pooled 22 studies, with 35 separate results, looking at memory, attention, anxiety and pain. It found an overall medium-sized effect in favour of binaural beats. The size and direction of the effect depended on the frequency used, how long people listened, and when they listened in relation to the task.
Other reviews have been less positive, particularly on attention and memory, and many individual studies are small.
The most consistent findings are for anxiety, especially before medical and dental procedures, where several trials report that patients who listened to binaural beats were calmer than those who did not.
How to reconcile the two
If brainwaves are not reliably entrained, why might people feel calmer? Several explanations do not need entrainment at all.
- Expectation. People are told the sound will relax them.
- Relaxing audio. Most recordings embed the tones in soothing music or nature sounds.
- Taking time out. Fifteen minutes with headphones on and eyes closed is restful whatever is playing.
- Distraction from worry or pain.
A fair test compares binaural beats with the same audio without the beat. Studies that do this find smaller effects, and sometimes none.
Claims with no good evidence
- Raising intelligence
- “Digital drugs” that mimic intoxication
- Treating ADHD, depression or other conditions
- Instant deep meditation
- Synchronising the two halves of the brain
- Any specific frequency healing the body
Binaural beats and hypnosis
Many hypnosis recordings have beats in the background. There is no good evidence that they deepen hypnosis or make suggestions more effective. If you like the sound, it does no harm. The work is done by the words, your attention and your willingness.
The contrast is worth stating. A binaural beat recording asks nothing of you. Hypnosis is something you take part in. Passive methods are attractive for that reason, and that is also why they tend to do less.
Is it safe?
For most people, yes. A few cautions:
- Keep the volume low. Long listening at high volume damages hearing.
- Not while driving or doing anything that needs alertness.
- If you have epilepsy, check with your doctor first. Rhythmic stimulation is usually a concern with flashing light more than sound, but it is sensible to ask.
- Stop if you get a headache, feel dizzy or uneasy.
- Do not use it in place of treatment for a medical or mental health condition.
If you want to try it
- Use headphones. It does not work through speakers.
- Pick a frequency for the purpose: lower for winding down, higher for alertness.
- Listen for fifteen to thirty minutes.
- Compare honestly with the same time spent listening to music you find relaxing.
- Keep whichever you prefer.
Similar products
Isochronic tones are a single tone pulsed on and off, needing no headphones. Monaural beats are two tones mixed before they reach the ear. The same doubts about entrainment apply to both.
The bottom line
A binaural beat is a real auditory illusion. Whether it tunes your brain is doubtful: most studies that looked did not find reliable entrainment. Some trials do find people feel calmer, most plausibly through relaxation and expectation. If you enjoy it, there is no harm in it. Just do not expect a pair of tones to do the work for you.
Next in the series: ASMR vs Hypnosis: Tingles, Trance and What They Share
This article is for general information and is not medical advice.