Binaural beats

What a binaural beat actually is

Play a 198 Hz sine tone into your left ear and 202 Hz into your right, and you'll hear something neither ear is receiving: a single tone that pulses, softly, four times per second. That pulse — the binaural beat — is manufactured in your brainstem, where a structure called the superior olivary complex compares timing between your ears. It's the same circuitry you use to locate sounds in space, caught doing something it never evolved for.

This generator does exactly that: a 200 Hz carrier, split so each ear gets carrier ± half the beat frequency, hard-panned left and right. Which is why headphones aren't a suggestion. Over speakers the tones blend in the air and you get an ordinary acoustic beat in the room — pleasant, but not the phenomenon.

The claim, and where it came from

The beat frequencies are named after EEG bands: delta (0.5–4 Hz) dominates deep sleep, theta (4–8 Hz) drowsiness and light sleep, alpha (8–13 Hz) relaxed wakefulness with eyes closed. The popular theory — "brainwave entrainment" — says listening to a 2 Hz beat nudges your brain toward 2 Hz activity, i.e., toward sleep. It's an elegant idea, first popularized after Gerald Oster's 1973 Scientific American article made binaural beats famous.

What the evidence supports

Three tiers, in descending order of confidence:

• The illusion: solid. The beat percept and its brainstem origin are textbook auditory neuroscience, reproduced for decades.
• Relaxation effects: mixed but not empty. A 2019 meta-analysis of 22 studies found a moderate overall effect on anxiety reduction — but the studies are small, varied, and hard to blind (you can hear what condition you're in). Some well-run studies find binaural beats no better than ordinary calming tones.
• Whole-brain entrainment: weak. EEG studies looking for the cortex synchronizing to the beat frequency report small, inconsistent effects. A 2023 systematic review concluded the entrainment hypothesis is not reliably supported.

The honest summary: this is a low-cost, low-risk practice with a real acoustic phenomenon at its core and modest, contested evidence for the benefits. Some nervous systems find the pulse settling. A theta track before sleep is a fine habit to keep — just keep it because it works for you, not because a thumbnail promised brain states on demand.

How to use the generator

• Headphones on. Any pair. Without them there is no binaural beat.
• Pick a preset: delta 2 Hz or theta 5 Hz before sleep; alpha 10 Hz for winding down while still awake. The presets share a 200 Hz carrier — low enough to be comfortable, high enough for small drivers.
• Volume low. Start at 30% and go quieter, not louder — the illusion works near the threshold of hearing, and loudness adds nothing but fatigue.
• Give it ten minutes. The percept sharpens as you settle. Set the 30-minute sleep timer and let it fade out after you're gone.
• Seizure history? Ask your doctor before using rhythmic auditory stimulation. Reported problems are rare; the question is still worth asking.

Where beats fit in a wind-down

A tone can carry your attention, but it has no words in it. That's its strength — nothing to follow — and its limit: it can't say anything back to the voice rehearsing tomorrow at 1 a.m. In practice, tones pair well with a short piece of spoken audio earlier in the wind-down: a few minutes of the AYA Method — a daily recording in your own future voice — then the theta pulse to carry you the rest of the way down. Words first, then the hum.

A two-week experiment worth actually running

Because the evidence is mixed and the cost is zero, the most useful study on binaural beats is the one with a sample size of you. The protocol that produces a readable answer:

• Week one, no beats. Keep your normal wind-down and log two numbers each morning: roughly how long you took to fall asleep, and how rested you feel from 1–5. Thirty seconds of logging, phone note is fine.
• Week two, add theta. Same wind-down, plus the 5 Hz preset at low volume for the last 20 minutes before lights out, headphones on, sleep timer set. Log the same two numbers.
• Compare medians, not memories. A night or two proves nothing either way — you're looking for a consistent shift across the week.

Two honest caveats. You can't blind yourself, so part of any improvement will be expectation — which still counts as an improvement, just not as neuroscience. And keep everything else fixed for the fortnight: caffeine timing, wake time, screens. A trial with three moving variables measures none of them. If week two wins, keep the habit and skip the debate. If it doesn't, you've spent nothing and learned something — try texture instead of tone.

If beats aren't for you

Plenty of sleepers prefer texture to tone. Brown noise gives you the low warmth without the pulse; pink noise is the balanced, rain-like middle; and the solfeggio tones are single pure frequencies with a long tradition attached, if that's the register you like. All of them run in this same lab, free, in your browser.