What is 40 Hz?
Hz means cycles per second, so a 40 Hz rhythm repeats 40 times a second. In the brain, 40 Hz sits in the gamma range (roughly 30 to 100 Hz), the fast rhythm seen when you're alert, focused or bringing information together.
40 Hz is too low to hear well as a plain tone, so 40 Hz audio is usually a normal tone pulsing on and off 40 times a second. That's what SleepHz plays: a 400 Hz tone pulsing at 40 Hz, which sounds like a soft, fast flutter.
What the 40 Hz studies found
At MIT (Martorell et al., Cell, 2019), mice bred to develop Alzheimer's-like disease heard short tone pips 40 times a second, for an hour a day. After a week, they had less amyloid plaque in hearing and memory areas of the brain and did better on memory tests; other rhythms didn't do this. Adding a 40 Hz flickering light reached even more of the brain.
Those were mouse studies. Early human trials of 40 Hz light and sound are running, but there's no proof yet that it prevents or treats Alzheimer's or any other condition. Treat 40 Hz as a focus sound, not medicine.
What is 40 Hz good for?
- Focus sessions: a steady, fast pulse to work or study along with.
- Gamma-wave listening: if you're curious about the 40 Hz research, this is the sound it's built on.
- Short daily sessions: the MIT mice listened for an hour a day; most people try 15 to 60 minutes.
Want something calmer? Alpha Calm (10 Hz) is gentler for relaxing, and Deep Sleep (2 Hz) is for bed.
40 Hz binaural beats vs a 40 Hz tone
A 40 Hz binaural beat plays two tones 40 Hz apart, one in each ear, and needs headphones. The 40 Hz pulse used in the MIT research is a sound that turns on and off 40 times a second, which works on any speaker. SleepHz uses the pulse, so you can play it out loud.
