40 Hz binaural beats
The single most-searched frequency on this site, and the one with the most research attention behind it — most of which is not about listening to a beat in a browser.
A 40 Hz binaural beat is made by playing two tones 40 Hz apart — 280 Hz and 320 Hz, for example. That is different from a 40 Hz tone, which is a very low pitch most speakers and all earbuds reproduce badly, and different again from 40 Hz light or click stimulation, which is what the laboratory research uses. The player above defaults to the beat.
Three different things people mean by “40 Hz”
| What | How it is produced | Where you meet it |
|---|---|---|
| 40 Hz binaural beat | Two tones 40 Hz apart, one per ear, headphones required | This page, most YouTube tracks |
| 40 Hz isochronic tone | One tone switched on and off 40 times a second, speakers fine | The second preset above |
| 40 Hz pure tone | An actual 40 Hz sine — a very low bass note | The fourth preset; needs a subwoofer to hear properly |
| 40 Hz sensory stimulation | Flickering light and/or clicks at 40 Hz, in a lab or device | The MIT research programme, clinical trials |
What the research actually says
The reason 40 Hz is famous is a line of work at MIT on gamma-frequency sensory stimulation in mice, followed by early-stage human trials of devices that deliver 40 Hz light and sound. It is genuinely interesting research and it is still preliminary — small human studies, results not yet settled, and it is being tested as a device-based intervention under clinical supervision.
Three things follow from that, and they matter more than the frequency does. It used flickering light and click trains, not binaural beats. It was not a browser tab. And it is not a treatment you can self-administer by pressing play — no result here supports claims about memory, dementia or brain health from listening to a 40 Hz beat.
We include 40 Hz because people look for it and because it is a perfectly good high-alertness setting. We are not going to attach a laboratory result to it that the laboratory did not produce. Our full position is on the evidence page.
How 40 Hz feels compared with slower beats
Fast. Below about 20 Hz a binaural beat is a slow sway between the ears; at 40 Hz it turns into a rough, continuous flutter, and many people find it noticeable rather than ambient. That makes it a poor background for long sessions and a reasonable choice for a short, deliberate block. If it grates, drop the carrier to 200 Hz or add a noise bed — both soften it considerably.
Carrier choice
- 200–300 Hz — the usual range. The beat is clearly audible and the tone is easy to sit with.
- Above 500 Hz — the beat becomes harder to perceive as the carrier rises; there is no benefit to a shrill carrier.
- Below 100 Hz — earbuds start to struggle and the beat gets muddy.
40 Hz on a phone
A browser tab stops when a phone screen locks, so a 40 Hz block on the move is one of the few cases where the mobile app is the better tool — it keeps playing in the background and works without a connection.
Questions
Do 40 Hz binaural beats improve memory?
There is no good evidence that they do. The memory research people are thinking of used 40 Hz light and click stimulation in laboratory settings, not binaural beats through headphones.
Is 40 Hz safe to listen to?
For most people, yes, at a moderate volume. Anyone with epilepsy or a seizure disorder should talk to a doctor first — rhythmic stimulation of any kind is worth checking. See safety.
Why can I barely hear the 40 Hz pure tone?
Because 40 Hz is near the bottom of human hearing and most headphones and laptop speakers do not reproduce it. What you feel is often more than what you hear.
How long should a 40 Hz session be?
20 to 40 minutes is typical. It is a more intrusive sound than slower beats, so most people use it in shorter blocks.
Does it work without headphones?
Not as a binaural beat. Use the isochronic preset, which pulses a single tone and carries over speakers.
Running this on a phone? The Brainwave Generator app keeps playing with the screen off, works without a connection, and carries the same engine. Free on iOS and Android.