Put on a pair of headphones. In your left ear, a steady tone at 200 Hz. In your right, another at 210 Hz. Neither tone wavers. Neither pulses. And yet, after a moment, you hear something that isn't in either of them: a slow, soft throb, rising and falling ten times a second, somewhere in the middle of your head.
That pulse is a binaural beat. It is one of the stranger facts about hearing: a sound your brain makes for you, out of two sounds that are really there. This entry explains how it happens, what the brainwave bands are, where the modern fascination came from, and what research has and hasn't found.
What are binaural beats?
Binaural beats are a pulsing sound you perceive when each ear hears a slightly different steady tone. The beat's rate equals the difference between the two frequencies: 200 Hz in one ear and 210 Hz in the other produce a beat of 10 Hz, ten pulses per second. The beat exists only in perception. It is not present in either tone, and it disappears if you take one earphone out.
How do binaural beats work?
The effect was first described in 1839 by the Prussian physicist Heinrich Wilhelm Dove. It happens because of the way your two ears are wired together.
Signals from each ear travel up into the brainstem, where they meet in a structure called the superior olivary complex. Its job is to compare the timing of sound arriving at each ear, which is how you tell where a sound is coming from. When the two ears receive tones a few hertz apart, the timing difference between them shifts steadily, round and round, and the brain experiences that rolling shift as a pulse.
Two details follow from this:
- Low tones work best. The brain's fine timing comparison works for tones below roughly 1,000 Hz, so binaural beats are heard most clearly with carrier tones in the low hundreds of hertz.
- Small differences work best. Up to around 30 Hz, the difference is heard as a beat. Beyond that it tends to become a roughness, or two separate tones.
Do you need headphones?
Yes. Binaural beats depend on each ear receiving only its own tone. Through speakers, both tones reach both ears, mix in the air, and make an ordinary acoustic beat instead. That is a real beat too, but a different thing. It helps to know the three kinds of pulsing tone apart:
| How it's made | Needs headphones? | |
|---|---|---|
| Binaural beats | A different steady tone in each ear; the beat is made in the brain | Yes |
| Monaural beats | Two tones mixed together before they reach you; the beat is in the sound itself | No |
| Isochronic tones | A single tone switched on and off at a steady rate | No |
The brainwave bands
The reason binaural beats are usually described in bands comes from brain research. The brain's electrical activity, measured with EEG, rises and falls in rhythms, and researchers group those rhythms into bands by speed. Each band is most prominent in particular states:
| Band | Range | Most prominent during |
|---|---|---|
| Delta (δ) | 0.5–4 Hz | Deep, dreamless sleep |
| Theta (θ) | 4–8 Hz | Drowsiness, light sleep, deep meditation |
| Alpha (α) | 8–13 Hz | Relaxed wakefulness, especially with eyes closed |
| Beta (β) | 13–30 Hz | Alert, active thinking and concentration |
| Gamma (γ) | 30 Hz and above | Focused attention and perception |
The idea behind most binaural beat recordings is called entrainment: that a beat at a given rate might nudge the brain's own rhythms towards the same rate, and so towards the state that goes with it. A 10 Hz beat for relaxed alpha, a 6 Hz beat for meditative theta, a 2 Hz beat for the slow waves of sleep. It is an appealing idea, and whether it happens is exactly what much of the research has set out to test.
From a physics curiosity to a practice
For more than a century, binaural beats were a laboratory curiosity. That changed in 1973, when the biophysicist Gerald Oster published "Auditory Beats in the Brain" in Scientific American. He described how the beats are produced, suggested they could be a tool for studying the brain, and brought them to a wide audience.
Around the same time, the American radio broadcaster Robert Monroe was experimenting with sound and consciousness. He developed a method of layering binaural beats that he called Hemi-Sync, and founded the Monroe Institute in Virginia to explore meditation, deep relaxation and altered states. His audio programme, the Gateway Experience, became one of the best known in the field.
Gateway gained a second life decades later. In 1983, a US Army officer, Lieutenant Colonel Wayne McDonnell, wrote a report analysing the Gateway method, and after it was made public through the CIA's online archive it spread widely on social media. Much of today's interest in binaural beats can be traced back to that unlikely document.
Binaural beats in meditation and spiritual practice
For many people, binaural beats are less a scientific question than a doorway. Meditators use slow theta beats to settle into the drowsy, image-rich edge between waking and sleep that many contemplative traditions describe. Others use alpha beats to mark the start of a quiet practice, or low delta beats as part of a wind-down ritual at night. In Monroe's work, and in the communities that grew from it, the beats were a vehicle for exploring consciousness itself: out-of-body experience, expanded awareness, states beyond ordinary attention.
Like a bell, a drone or a repeated chant, a steady pulse gives the attention something to rest on, and many listeners find that is where the practice begins.
What does the research say?
Research on binaural beats is genuinely active, and the results are mixed.
- A 2019 meta-analysis by Garcia-Argibay and colleagues combined 22 studies and found small to moderate effects of binaural beats on anxiety, memory, attention and the perception of pain. The results varied a great deal from study to study.
- A 2023 systematic review in PLOS ONE looked specifically at whether binaural beats change the brain's rhythms, the entrainment idea. Of the 14 EEG studies it examined, five reported results in line with entrainment, eight reported contradictory results, and one was mixed.
- Some individual trials have reported encouraging results in specific settings. One well-known 2005 study found lower anxiety before surgery in patients who listened to binaural beats compared with those who didn't.
The honest summary is that binaural beats may have modest effects for some people in some situations, but the evidence is inconsistent, the idea of entrainment is not established, and they are not a treatment for any condition. The question is interesting enough that researchers keep studying it, and there is plenty still to understand.
Are binaural beats safe?
For most people, yes. Listening to binaural beats at a low, comfortable volume is like listening to any other quiet sound. The main things to watch are volume, since pure tones through headphones can feel louder than they are, and circumstance: because they are often used for relaxation or sleep, don't listen while driving or doing anything that needs your full attention.
How to listen
- Use headphones. Check that left and right are the right way round.
- Keep it quiet. Start lower than feels natural. A beat is easier to notice at a soft volume than a loud one.
- Choose a low carrier. Tones between about 100 and 500 Hz give the clearest beats.
- Start with alpha. A 10 Hz beat is easy to hear and a gentle introduction.
- Give it time. Ten to twenty minutes, eyes closed, is a common session. A little soft background noise can make longer listening more comfortable.
- Notice rather than expect. Pay attention to what actually happens, rather than to what you think should.
Try it in the Lab
The Binaural Beat Generator lets you set a tone for each ear, or start from a brainwave band, and shows the two waves and the beat they make together. You can take the carrier tone from the Frequency Library, add a soft noise bed, and set a timer that fades out gently. Explore the Sleep, Meditation and Focus intentions for the tones traditions pair with those states.
Sources & further reading
- Oster, G. (1973). Auditory beats in the brain. Scientific American, 229(4), 94–102.
- 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, 357–372.
- 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.
- Padmanabhan, R., Hildreth, A. J. & Laws, D. (2005). A prospective, randomised, controlled study examining binaural beat audio and pre-operative anxiety in patients undergoing general anaesthesia for day case surgery. Anaesthesia, 60(9), 874–877.
- Chaieb, L., Wilpert, E. C., Reber, T. P. & Fell, J. (2015). Auditory beat stimulation and its effects on cognition and mood states. Frontiers in Psychiatry, 6, 70.