- A 40 Hz binaural beat is made of two tones that differ by 40 Hz, for example 300 Hz and 340 Hz.
- Gamma waves are the fastest rhythm of the brain, 30 to 100 Hz; 40 Hz is the frequency studied most.
- The brain answers a 40 Hz binaural beat with a measurable 40 Hz response, but only when the tones are low, around 400 Hz; above 3000 Hz it disappears.
- Three minutes of a 40 Hz beat before and during a task made attention more focused on detail than a constant tone.
- Gamma beats made thinking more flexible in a dual-task study.
- MIT's research on 40 Hz and Alzheimer's disease uses flickering light and pulsed sound, not binaural beats.
What are 40 Hz gamma waves
The brain produces electrical rhythms of different speeds. Delta is the slowest and belongs to deep sleep; gamma is the fastest, 30 to 100 Hz, and appears when the brain binds information together: recognising a face, holding several things in mind, solving a problem.
Within the gamma band 40 Hz has a special place. It is the frequency at which the hearing system follows a rhythmic sound most readily, which is why audiologists and neuroscientists have used 40 Hz sounds for decades.
Gamma waves, attention and meditation
Gamma is usually linked to effort, and the most striking recording of it comes from stillness. In 2004 researchers at the University of Wisconsin recorded the brain activity of Buddhist monks with many years of practice. During meditation they produced sustained gamma oscillations of unusually high amplitude, synchronised across distant areas of the brain, and their gamma activity was higher than in beginners even at rest.
The finding changed how gamma is understood: not as a sign of strain, but as a sign of a brain that holds many things together at once. It also set expectations that sound cannot meet. The monks' gamma was the result of thousands of hours of training, not of listening.
What do 40 Hz binaural beats do
First, the brain registers them. In a Canadian study each ear received a different tone, 40 Hz apart, and the recording of brain activity showed a steady response at exactly 40 Hz, although no 40 Hz sound was present in either ear. The response appeared with low tones around 400 Hz and became undetectable above 3000 Hz. It was smaller than the response to a beat that is physically present in the sound.
Second, they change how people perform. The results come from Leiden University, where three studies used the same setup: a 40 Hz beat against a constant 340 Hz tone.
| Study | Task | Result with the 40 Hz beat |
|---|---|---|
| Colzato and colleagues, 2017 | Seeing the detail or the whole of a figure | Attention became more focused on detail |
| Reedijk and colleagues, 2015 | Catching two targets in a rapid stream | The lapse of attention disappeared, but only in people with a low eye-blink rate |
| Hommel and colleagues, 2016 | Doing two tasks at once | Thinking became more flexible |
These are effects on healthy adults during a task. They are real and modest: a 40 Hz beat is a nudge towards alertness, not a change of ability.
40 Hz binaural beats benefits: what is shown and what is not
Lists of benefits on the internet mix results from different methods. Here they are sorted by what was actually tested.
| Claim | Status | Source |
|---|---|---|
| The brain responds at 40 Hz | Measured | Recordings of brain activity with low carrier tones |
| Sharper attention to detail | Shown in healthy adults | Leiden study, 2017 |
| More flexible thinking | Shown in healthy adults | Leiden study, 2016 |
| Fewer lapses of attention | Shown in some people only | Leiden study, 2015 |
| Better memory | Not tested with 40 Hz; shown with 20 Hz beta | Memory study, 2019 |
| Protection against Alzheimer's disease | Not tested with binaural beats | MIT research uses light and pulsed sound |
| Better sleep | No; gamma is an activating rhythm | — |
Which tones make the best 40 Hz binaural beat
Any two tones 40 Hz apart give a 40 Hz beat, but the brain does not respond to all pairs equally. In the recording study the response was clear with tones around 400 Hz and disappeared above 3000 Hz.
| Left ear | Right ear | How it sounds |
|---|---|---|
| 200 Hz | 240 Hz | Low and soft, the beat is easy to hear |
| 300 Hz | 340 Hz | The default of this generator; a comfortable middle |
| 400 Hz | 440 Hz | Brighter; the range used in the brain recording study |
| Above 1000 Hz | The binaural beat weakens and then disappears |
A difference of 40 Hz is large, so the two tones are heard as a slightly rough chord instead of one wavering tone. That roughness is normal.
40 Hz binaural beats for studying and focus
In the Leiden studies people listened for three minutes before the task and continued during it. That is the pattern to copy.
- Start the beat a few minutes before you begin and keep it on during the first block of work.
- Use it for tasks that need precision: proofreading, calculations, code review, learning formulas.
- Keep the volume low. A 40 Hz beat sounds like a rough buzz, and loudness makes it tiring, not stronger.
- For long reading or writing sessions a beta beat of 15 to 20 Hz is softer and has more evidence; see the page on binaural beats for focus.
- Stop in the evening. Gamma is an activating rhythm.
How long to listen to 40 Hz binaural beats
In the attention studies the sessions were short: three minutes before the task and the length of the task itself. In the brain recording study ten minutes were enough to measure the response.
For everyday use 10 to 20 minutes at the start of a working block is a sensible length. The MIT protocol of an hour a day belongs to a different method and a different purpose.
40 Hz, MIT and Alzheimer's disease
Much of the interest in 40 Hz comes from research at the Massachusetts Institute of Technology. In mice that model Alzheimer's disease, light flickering 40 times a second reduced amyloid in the brain, and later experiments added a sound pulsing at the same rate. The method is called GENUS, gamma entrainment using sensory stimulation.
In 2022 the first results in people were published. In a small pilot study 15 patients with mild Alzheimer's dementia used a device with 40 Hz light and sound every day for three months. It was safe and well tolerated, and the group with 40 Hz stimulation showed less shrinkage of the hippocampus and did better in a memory test than the control group. Larger trials are under way.
This research does not use binaural beats. The sound in GENUS is physically pulsed, it is combined with light, and it is delivered daily for months. No study has shown that 40 Hz binaural beats affect Alzheimer's disease, and they should not be used in place of medical care.
40 Hz binaural beat, isochronic tone or pure tone
The same number hides three different sounds.
| Sound | What you hear | Headphones | Note |
|---|---|---|---|
| 40 Hz binaural beat | Two tones, a rough wavering between them | Required | The beat is created in the brain |
| 40 Hz isochronic tone | One tone switched on and off 40 times a second | Not required | The pulse is in the sound; the brain response is stronger |
| 40 Hz pure tone | A very low hum at the edge of hearing | Not required | Phone and laptop speakers cannot reproduce it |
If you search for a 40 Hz pure tone and hear nothing on your phone, the speaker is the reason. For a 40 Hz rhythm use the binaural or the isochronic mode, where the carrier tone is well within the range of any headphones.
Can you use 40 Hz binaural beats for sleep
No. Gamma is the rhythm of an active brain, and the studies with 40 Hz beats measured attention. For sleep use a delta beat of 2 to 3 Hz, and for calming down an alpha beat of 10 Hz.
Is 40 Hz safe
In the studies with healthy adults no harm was reported. In the MIT pilot study daily 40 Hz stimulation for three months was well tolerated.
The usual cautions apply: keep the volume low, do not listen while driving, stop if you get a headache or feel uneasy. People with epilepsy should talk to their doctor before using any rhythmic sound or light.
Questions people ask
What do 40 Hz binaural beats do?
In studies with healthy adults a 40 Hz beat made attention more focused on detail and thinking more flexible. The brain answers the beat with a measurable 40 Hz response.
What are the benefits of 40 Hz binaural beats?
Sharper attention during demanding tasks. The effects found in studies are modest and differ between people.
How do I make a 40 Hz binaural beat?
Play two tones that differ by 40 Hz, one in each ear, for example 300 Hz and 340 Hz. Both tones should be low: the brain response disappears with tones above 3000 Hz.
Are 40 Hz binaural beats good for studying?
They suit tasks that need precision. Listen for a few minutes before the task and during it. For long reading a beta beat is softer.
Do 40 Hz binaural beats help with Alzheimer's?
No study has shown that. The MIT research uses 40 Hz flickering light and pulsed sound delivered by a device, not binaural beats.
Can I sleep with 40 Hz binaural beats?
It is not recommended. Gamma is an activating rhythm. For sleep use a delta beat of 2 to 3 Hz.
Why can't I hear a 40 Hz pure tone?
40 Hz is a very low sound that small speakers cannot reproduce. In a binaural beat the tones you hear are 300 and 340 Hz, and 40 Hz is only their difference.
Is a 40 Hz isochronic tone better than a binaural beat?
A sound whose pulse is physically present evokes a stronger brain response than a binaural beat, and it needs no headphones. Whether it works better for a task has not been compared.
- Schwarz D. W. F., Taylor P. Human auditory steady state responses to binaural and monaural beats. Clinical Neurophysiology, 2005, 116 (3), 658–668.
- Colzato L. S., Barone H., Sellaro R., Hommel B. More attentional focusing through binaural beats: evidence from the global-local task. Psychological Research, 2017, 81, 271–277.
- Reedijk S. A., Bolders A., Colzato L. S., Hommel B. Eliminating the attentional blink through binaural beats: a case for tailored cognitive enhancement. Frontiers in Psychiatry, 2015, 6, 82.
- Hommel B., Sellaro R., Fischer R., Borg S., Colzato L. S. High-frequency binaural beats increase cognitive flexibility: evidence from dual-task crosstalk. Frontiers in Psychology, 2016, 7, 1287.
- Iaccarino H. F. et al. Gamma frequency entrainment attenuates amyloid load and modifies microglia. Nature, 2016, 540, 230–235.
- Chan D. et al. Gamma frequency sensory stimulation in mild probable Alzheimer's dementia patients: results of feasibility and pilot studies. PLoS ONE, 2022, 17 (12), e0278412.
- Orozco Perez H. D., Dumas G., Lehmann A. Binaural beats through the auditory pathway: from brainstem to connectivity patterns. eNeuro, 2020, 7 (2).
The generator makes the sound in the browser (Web Audio). On this page it starts in binaural mode with a 300 Hz tone in the left ear and a 340 Hz tone in the right ear, which gives a 40 Hz gamma beat, and with a 15-minute timer. At the end of the timer the sound fades out gradually. All values can be changed.