Tomiwa Adey

← Notes

The strange promise of 40Hz

A week of 40Hz sound changed Alzheimer's-related amyloid markers in aged monkeys. Interesting, but nowhere near proven.

Written Sept 2026

This is a research note, not medical advice. The evidence is still early and 40Hz sound has not been proven to prevent or treat Alzheimer's disease.

I came across an Alzheimer's study with a result that sounds almost too simple.

Researchers played a sound to nine aged rhesus monkeys for one hour a day, seven days in a row. The sound was a 1kHz tone delivered in very short bursts, 40 times every second.

Then something changed.

A strange result#

After seven days, the amount of amyloid-beta in the monkeys' cerebrospinal fluid had risen by more than 200%.

That sounds bad. Alzheimer's is associated with amyloid building up in the brain, so why would more of it be interesting?

The researchers think the sound may have helped move amyloid out of the brain tissue and into the fluid around it, where it could be cleared. But that movement was inferred from the fluid measurements. They did not directly watch the amyloid leave the brain. Tau levels did not change either.

A five-minute demonstration generated from the study protocol: a 1kHz carrier tone, with a one-millisecond burst every 25 milliseconds. It does not reproduce the study's calibrated listening level, so start with your volume low.

What it actually means#

Does listening to 40Hz sound prevent Alzheimer's?

We do not know.

Earlier mouse studies found that 40Hz light and sound changed amyloid pathology. Small human studies have also shown that the stimulation can reach the brain and appears reasonably well tolerated. But the latest review of controlled trials says the effect on cognition and daily functioning is still not established.

Nine monkeys give us a reason to keep researching. They do not give us a treatment.

Why I am watching it#

The part I find interesting is the form of the possible treatment.

Not a new drug. Light and sound.

If this survives larger human trials, a cheap and non-invasive stimulus could matter. But it still has to survive those trials.

Promising is the right word. Proven is not.

Research sources