EARS & WAVES

← Frequencies

40 Hz.

The rhythm researchers use for gamma stimulation: 40 clicks a second. Listen to it, compare it with a 40 Hz tone and a 40 Hz binaural beat, and read what the science actually says.

Now playing Deep sleep

Listen

Tap an example to play it, and again to pause. Keep the volume comfortable: the clicks are meant to be heard, not to be loud.

What the research says

At MIT, Li-Huei Tsai’s lab found that light flickering and sound clicking 40 times a second strengthened 40 Hz “gamma” rhythms in the brains of mice with Alzheimer’s-like disease, with less amyloid and better memory. The effects faded about a week after the stimulation stopped.

In people the evidence is still small: studies with a few dozen patients, and a follow-up of five volunteers over two years, showed hints of slower decline. A large trial with 670 participants, the HOPE study by Cognito Therapeutics, is under way, and its device is not on sale.

Facts that often get mixed up

  • “40 Hz” in this research is a rhythm: short sounds repeating 40 times a second. A 40 Hz tone is something else, a deep hum that many phone and laptop speakers cannot play.
  • The studies combined light and sound. Flickering light can trigger seizures in people with photosensitive epilepsy; this page plays sound only.
  • Binaural beats were not used in these studies. The 40 Hz beat here is only for comparison.
  • This is not a treatment for Alzheimer’s or anything else. If you are worried about your memory, see a doctor.
In the studiesOn this page
What playsLight flicker and sound clicks together, 40 times a secondSound only: 40 clicks a second, a 40 Hz tone or a 40 Hz beat
Who it was forMice, and small groups of people with mild Alzheimer’sAnyone curious to hear it
How longAbout an hour a day, for weeks or monthsAs long as you like
What it claimsA possibly slower decline, still being testedNothing: it is for listening, not a treatment
Can 40 Hz sound prevent Alzheimer’s?

Not shown. The results so far come from mice and small groups of patients, and a large trial is still running.

Why clicks and not a tone?

Brain rhythms follow sharp, repeating events best. The studies used short sounds 40 times a second, which is what the first example plays.

Is it safe to listen?

At a comfortable volume, yes: it is just a sound. Stop if it gives you a headache, and keep the volume moderate in headphones.

Mixes

Pick what you need. One tap to start, change anything and save it as your own.

Focus timer

Work in waves.

The Pomodoro rhythm: focus with calm sound in your ears, then take a real break. A soft bell marks every change, so you never watch the clock. Every fourth break is a long one.

25:00Focus · 1 of 4

Sound while you work

Breathe

Slow your breathing down.

Follow the circle and the sound: it rises as you breathe in and falls as you breathe out. Choose a rhythm, or set your own, and pick what plays underneath.

Ready

Sound while you breathe

Noise generator

Any color of noise, from deep brown to bright violet — and everything in between.

Brown noise
Spectrum · 20 Hz – 20 kHz

Sound science

The colors of noise

Same randomness, different tilt. Each color shifts energy between low and high pitches — here is what that sounds like.

White

0 dB / octave

Equal energy at every frequency. Because we hear in octaves, it sounds bright and hissy — the classic "TV static".

Pink

−3 dB / octave

Equal energy in every octave, so it sounds even to the ear. Steady rain, rustling leaves. A favorite for focus.

Brown

−6 dB / octave

Deep and warm, like a distant waterfall or a plane cabin. Masks voices and traffic without any hiss.

Grey

Equal-loudness curve

Shaped around how our hearing works, so every pitch seems equally loud. Balanced and soft.

Blue

+3 dB / octave

The mirror of pink: more treble than bass. Airy, crisp, like a light spray.

Violet

+6 dB / octave

Mostly treble, like hissing water. Sometimes used to mask high-pitched ringing.

Calm

Gentle tones to settle into: singing bowls, a slow warm drone, wind chimes tuned so every note fits.

Frequencies

Famous tones on pages of their own: hear them side by side, with honest facts.

Sound phenomena

How sound bends, shifts, rings and fools the ear, and why space is silent: hear it for yourself.

Nature

Rooms & travel

Animals & countryside

A purring cat, whales and dolphins, a nightingale in the dark, cowbells on a summer pasture. Wonderful in stereo.

For babies

Womb sounds are what a baby heard for nine months: a deep rush of blood flow, and the heartbeat.

Hearing and speaker tests

Check your ears, headphones and speakers, each test on a page of its own with a live picture.

Ear Age · 60 seconds

Test your ears.

Our ears lose the highest pitches first, and it starts early. Find the highest tone you can still hear and see the typical age for it.

  • Headphones on, quiet room
  • Set a comfortable volume on the 1 kHz tone
  • Don't turn it up when a tone disappears — that's the point
20,000Hz

Can you still hear it?

Hearing age test →

More ear tests

Check your headphones, find the deepest bass your setup can play, or play any pitch you like.

Headphones check

Left & right

Each ear should get its own side. It matters for 8D, binaural beats and every stereo sound here.

Headphones on, then tap a side.

Bass test

How low can you go?

Deep tones from 200 Hz down to 20 Hz, the bottom of human hearing. Mostly it tests your speakers or headphones.

Tone generator

Any pitch, 20 Hz – 20 kHz

Hz

Start quiet: high tones and square waves get tiring fast.

Take it to bed

An app without the app store.

Add Ears & Waves to your home screen and it opens like any app — full screen, with its own icon. Everything it needs is saved on your device, so it keeps playing on a plane, in a tent or with Wi-Fi off.

Preparing offline mode…
  • Works offlineNo streaming. Sound is computed on your device, forever.
  • Screen offKeeps playing with the phone locked. The timer fades it out gently.
  • PrivateNo account, no ads, no cookies. Your mixes stay on your device.
Deep sleep