A binaural beat generator you can hear in the browser

Two things, and nothing else: a sine tone in your left ear and a slightly different sine tone in your right. Neither one contains a pulse. Play them together over headphones and you hear a third thing anyway — a slow throb at the difference between them.

That throb is the binaural beat. It is not present in the sound arriving at either ear, which is why speakers do not work: they let the two tones combine in the air first, and what you get instead is ordinary acoustic beating. Gerald Oster set the effect out in Scientific American in 1973, and the description has not changed since.

Everything here happens live in the page. The tones are synthesised by your browser for as long as you hold Play and stop existing when you release it — there is no file behind them, and nothing leaves your device.

You choose two numbers. The carrier is the pitch you actually hear. The beat is how far apart the ears are. The generator then splits the beat evenly either side of the carrier:

• left ear = carrier − beat ÷ 2
• right ear = carrier + beat ÷ 2

So a 200 Hz carrier with a 6 Hz beat gives 197 Hz on the left and 203 Hz on the right. The difference is 6 Hz, and the pitch you perceive stays at the 200 Hz you asked for rather than drifting upward — which is the only reason for splitting it rather than adding the whole beat to one side. Swapping the two ears sounds identical.

Oster reported that binaural beats are heard most clearly at carriers around 440 Hz, become less distinct as the carrier rises, and are not reported above roughly 900 to 1,000 Hz, with the differences that produce a usable beat sitting between about 1 and 30 Hz. The carrier here spans 100 to 400 Hz, matching what the app allows; the beat spans 0.5 to 40 Hz, which covers every band below.

EEG activity is conventionally grouped into named bands, and the five buttons above jump the beat into each one. The ranges are the app’s own. They are naming conventions rather than fixed facts: published boundaries differ between sources, so treat a band edge as a rough landmark and not a threshold you cross.

Delta 0.5–4 Hz

The slowest rhythm, dominant in dreamless deep sleep. The floor a night-time journey settles onto.

Theta 4–8 Hz

The drowsy edge between waking and sleep. Deep meditation and drifting, image-rich states tend to live here.

Alpha 8–13 Hz

The relaxed idle. Awake and unhurried, thinking loosened but not gone. The bridge between focus and drift.

Beta 13–30 Hz

Ordinary waking attention — analysing, deciding, holding a task in mind. Where most of the day is spent.

Gamma 30–40 Hz

The fastest rhythm, associated with moments when attention snaps together and everything feels sharply bound.

What these describe is which rhythm tends to dominate the EEG in an ordinary state — delta in dreamless deep sleep, alpha in relaxed wakefulness. That is a correlation observed in recordings of the brain. It is not evidence that playing a beat at the same number produces the state, which is a separate question and the one the research below is about.

Mostly to find out what a beat sounds like before committing an hour to one. A few minutes with the sliders tells you more than any amount of reading: how slow half a hertz actually is, how a 6 Hz sway differs from an 18 Hz flutter, how much the carrier changes the character of the tone while leaving the beat alone.

Beyond that, people use a fixed tone as something to work or sit alongside — on while reading or writing, quietly under a task, or as a steady thing to return attention to during meditation practice. Those are descriptions of what people do, not claims about what it does to them.

A few practical notes. Both headphone sides must be connected, and any mono downmix setting removes the effect entirely — see why binaural beats need stereo headphones. And a single unchanging beat is the simplest case; most listening in practice moves between frequencies over a session rather than sitting on one.

Keep the volume low, too. The beat is a difference between two frequencies rather than a level, so turning it up adds exposure without making the sway any clearer. The WHO and ITU safe-listening standard treats 80 dB(A) over 40 hours a week as an adult reference exposure, and headphone sessions accumulate against that faster than most people expect.

That two separated tones produce a perceived beat is settled. What listening to one does is not, and the evidence is best read in two parts.

Outcomes

A 2019 meta-analysis of 22 studies, pooling 35 effect sizes, reported an overall medium effect of binaural-beat exposure across memory, attention, anxiety and pain (Hedges’ g = 0.45). That is a real signal, drawn from a small and varied literature rather than from large trials.

Whether the brain follows the beat

The mechanism usually offered — that brain rhythms synchronise to the beat, or “entrain” — is the part that does not hold up cleanly. A 2023 systematic review of studies measuring brain oscillatory activity during binaural-beat stimulation found fourteen eligible studies: five reported results consistent with the entrainment hypothesis, eight reported contradictory results, and one was mixed. Its authors concluded that studies attributing psychological or physiological change to entrainment do so without consistent supporting evidence.

Read together: something may happen for some people some of the time, and the popular explanation for why is not currently supported. Picking a beat because a band is “the sleep frequency” rests on the part of the story that is weakest.

The studies are small. Typical samples run to a few dozen participants, often undergraduates, tested once in a laboratory — which is far from the way anyone uses this at home over weeks.

The stimuli are not comparable either. Carrier frequency, beat frequency, session length, whether masking noise or music is layered underneath, and whether the beat plays before or during a task all vary between studies. The 2023 review makes this the centre of its critique: the outcomes disagree partly because the protocols are not the same thing.

Expectation is largely uncontrolled. A convincing placebo for audio is hard to build — participants can usually tell whether they are hearing a beat — so pooled effects on self-reported outcomes such as anxiety and mood carry an unknown amount of expectation with them. Blinding is rarely reported.

And almost nothing has been tested at the scale of ordinary use: long sessions, sessions every night, whether a beat that moves over time behaves differently from a fixed one, or whether any of it holds up beyond the first few weeks. Those questions are open, and a page that answered them confidently would be making the answers up.

This tool holds one beat still. That is the right way to understand the mechanism and the wrong way to spend forty minutes — a single unchanging frequency is a demonstration, not a session.

Mind Journeys plays the same two tones, and moves them. A journey is an ordered set of steps, each gliding the beat from one value to another over a set time: Gentle Descent opens at 10 Hz, eases to 6 Hz over eight minutes, then down to 3.5 Hz and finally toward 2 Hz across half an hour. Each step can carry its own background — rain, ocean, pink noise, or nothing but the tone — and you can drag along the curve mid-session to move to any point in it.

Which frequency should I set?

There is no correct number, and anyone offering one is ahead of the evidence. People generally pick a beat in the band they associate with the state they are after — lower for winding down, higher for working — and a carrier that simply sounds comfortable, usually somewhere between 160 and 240 Hz. Starting at 6 Hz in theta is as good a place as any. Move the slider and keep whatever you find easiest to ignore.

What does the carrier frequency change?

The carrier is the pitch you actually hear; the beat is the gap between the two ears, riding on it. Changing the carrier makes the tone higher or lower without changing the beat. Oster reported binaural beats being heard most clearly at carriers around 440 Hz, becoming less distinct as the carrier rises, and not reported above roughly 900 to 1,000 Hz. This tool spans 100 to 400 Hz, the range the app offers.

Why is the left ear lower than the right?

Only the difference between the two ears matters, so which ear gets the higher tone is a convention rather than a requirement. Splitting the beat evenly either side of the carrier — left at carrier minus half the beat, right at carrier plus half — keeps the perceived pitch at the carrier you chose. Swapping the two sounds the same.

Can I download or save the tone?

No. This is a live generator: the two tones are synthesised in the page while you listen, and nothing is written to a file, so there is nothing to export, save or share. If you want something you can keep and replay — a beat that moves over time, with ambience underneath — that is what the app is for.

How long can I listen for?

As long as it stays comfortable, with the volume low. The beat is a difference between two frequencies rather than a level, so turning it up adds exposure and nothing else. The WHO and ITU safe-listening standard treats 80 dB(A) over 40 hours a week as an adult reference exposure, and headphone sessions add up against that faster than most people expect.

I cannot hear any pulsing — what is wrong?

Check that both sides of your headphones are connected, and that no mono setting is combining the channels; iOS has one under Accessibility, Audio & Visual, Mono Audio. Very low beats are slow rather than obviously rhythmic — half a hertz is one sway every two seconds. And the sway is meant to be subtle at a low volume, which is not a sign it has failed.

• what a binaural beat is and how one is madeThe pillar explainer: the two tones, the perceived beat, and where the evidence currently stands.
• why binaural beats need stereo headphonesWhy speakers cancel the effect, what to listen on, and how loud is too loud.
• how theta waves are definedThe drowsy edge between waking and sleep, and the band most meditation journeys sit in.
• what delta waves are and how they are scoredThe slowest rhythm, dominant in dreamless deep sleep and the floor a night-time journey settles onto.

Browse all guides — the binaural beat and brainwave explainers, grouped by topic.

1. Oster, G. (1973). Auditory beats in the brain. Scientific American, 229(4), 94–102. https://doi.org/10.1038/scientificamerican1073-94
2. Garcia-Argibay, M., Santed, M. A., & Reales, J. M. (2019). Efficacy of binaural auditory beats in cognition, anxiety, and pain perception: a meta-analysis. Psychological Research, 83(2), 357–372. https://doi.org/10.1007/s00426-018-1066-8
3. Ingendoh, R. M., Posny, E. S., & Heine, A. (2023). Binaural beats to entrain the brain? A systematic review of the effects of binaural beat stimulation on brain oscillatory activity, and the implications for psychological research and intervention. PLOS ONE, 18(5), e0286023. https://doi.org/10.1371/journal.pone.0286023
4. World Health Organization & International Telecommunication Union (2019). Safe listening devices and systems: a WHO-ITU standard (ITU-T Recommendation H.870). https://www.who.int/publications/i/item/9789241515276