What is 40 Hz?
40 Hz is a very low bass tone that matches the brain’s gamma rhythm; on a vibrating plate it produces a few large, simple nodal regions.
40 Hz sits near the bottom of the human hearing range — you feel it as much as you hear it. It is lower than the lowest note of a standard bass guitar (E1, about 41.2 Hz), so it is close to the fundamental of that string.
The number is also famous in neuroscience. Brain waves around 40 Hz are called gamma oscillations, and since 2016 researchers at MIT have studied whether flickering light and sound at 40 Hz affect Alzheimer’s-related changes in mice. Early human trials are under way, but results are preliminary and 40 Hz audio is not an approved treatment.
| Nearest note (A4 = 440 Hz) | D♯1 (38.9 Hz), +49 cents |
|---|---|
| Wavelength in air | 857.5 cm |
| Period | 25 ms per cycle |
| Simulator Chladni mode | (1, 1) |
What the 40 Hz pattern looks like
At such a low frequency the plate vibrates in its simplest shapes, so expect a small number of broad cells rather than fine lines. Polar mode shows this well as a few wide rings.
The simulator above is already set to 40 Hz. Press Play in the Slider tab to hear the tone, switch pattern modes to compare shapes, and use Record video or Export PNG to keep the result. The address bar always holds a link to exactly what you see, so you can share it.
40 Hz FAQ
Can you hear 40 Hz?
Yes, most people can hear 40 Hz, but small speakers and phone speakers often cannot reproduce it. Use headphones or a subwoofer for the real sound.
Does 40 Hz sound help with Alzheimer’s?
It is an active research area. Studies in mice are promising and human trials are running, but there is not yet enough evidence to use 40 Hz sound as a treatment.