A moment to understand · Brainwave entrainment
Three ways to make a beat.
Play a steady pulse of sound and part of the brain's response falls into step with it. That is what entrainment means. Here is how binaural beats, monaural beats and isochronic tones make that pulse, why 40 Hz stands out, and what the research does and does not show. 74 seconds, narrated, with captions.
Part of A moment to understand, short explainers on the ideas behind my four free brain apps.
What entrainment means
Brain activity has rhythms, measured in hertz, or cycles per second. When you listen to a sound that pulses at a steady rate, the part of the brain that handles hearing produces a response at that same rate, and it can be picked up with sensors on the scalp. That is the solid, measurable part of entrainment.
It is not the same as the whole brain switching into a new state. A preset labelled 10 Hz tells you the rate of the sound. It is not a reading of your brain, and it does not guarantee your brain is doing anything in particular.
Three ways to make a beat
- Binaural beatsA slightly different tone goes to each ear, for example 200 Hz on the left and 210 Hz on the right. The brain hears the 10 Hz difference as a soft beat. Because the two tones have to stay separate, you need headphones. Try binaural.
- Monaural beatsThe two tones are mixed together before they reach you, so the beat is already in the sound. Any speaker works. This is what the one-tap player on Brain Beats uses. Open Brain Beats.
- Isochronic tonesA single tone switches on and off at a steady rate. Of the three, it gives the most obvious pulse to the ear. That does not mean it works better. Try isochronic.
Why 40 Hz stands out
In people who are awake, the brain's response to a pulsing sound is especially strong at around 40 pulses a second. Researchers call it the auditory steady-state response, and it has been measured reliably for decades. That is why 40 Hz sound gets so much attention in brain research.
A strong response is not the same as a benefit, though. Much of the widely shared 40 Hz research on memory and Alzheimer's disease was done in mice, and the human studies so far are small pilot studies, often using light and sound together through dedicated equipment. Brain Beats is sound only and is not the same as those protocols. Nothing here shows that listening to 40 Hz prevents or treats dementia.
What the research shows, and what it does not
A 2019 analysis that pooled 22 binaural-beat studies found a moderate effect overall on memory, attention, anxiety and pain. Results varied a lot with the task, the sound settings and how long people listened. Studies that measure brain waves directly are split: in a 2023 review of 14 of them, five supported binaural entrainment, eight did not, and one was mixed.
So people use these rhythms to relax, to wind down before sleep, or to give focused work a steady background. Those are reasonable uses, not promised results. The evidence for attention is mixed, and sound can compete with a hard task. If it distracts you or feels unpleasant, turn it off.
Listening safely
- Keep the volume lowLouder is not stronger. Start low, keep it comfortable, and stop if it bothers you.
- Use a timerBrain Beats can fade out on its own after 5, 15 or 30 minutes, which is handy for winding down.
- SeizuresIf you have epilepsy, a seizure disorder, or a history of seizures, check with a doctor before using rhythmic stimulation. This is a precaution. Brain Beats uses sound only, with no flashing light.
Brain Beats is a listening and relaxation tool. It is not a medical device or a treatment for anxiety, insomnia or any other condition.
Transcript
0:00Brain activity has rhythms, measured in cycles per second, or hertz. With a steady sound pulse, part of the brain's response follows that rate. That following is called entrainment.
0:13Binaural beats use a different tone in each ear. Your brain creates the beat, so you need headphones. Monaural beats mix the beat into the sound. Any speaker works. Isochronic tones switch one tone on and off, making the most obvious pulse.
0:31While awake, our auditory response is especially strong near forty hertz. This well measured response is called the auditory steady-state response. Forty hertz sound is an active area of brain research.
0:45People use these rhythms to relax, wind down before sleep, or accompany focused work. Brain Beats offers six presets for different listening goals.
0:55Pick a state, start at low volume, and set a timer so it fades out. The one-tap player uses monaural beats and works on speakers.
1:05Brain Beats is free and runs in your browser.
Sources
- Picton et al., 2003. Human auditory steady-state responses. International Journal of Audiology. The measured response to pulsing sound, and why it is strongest near 40 Hz in people who are awake.
- Garcia-Argibay et al., 2019. Efficacy of binaural auditory beats in cognition, anxiety, and pain perception: a meta-analysis. Psychological Research. 22 studies pooled; effects depend on the task and settings.
- Ingendoh et al., 2023. Binaural beats to entrain the brain? A systematic review. PLOS ONE. EEG studies of binaural entrainment are split.
- Martorell et al., 2019. Multi-sensory gamma stimulation ameliorates Alzheimer's-associated pathology and improves cognition. Cell. 40 Hz sound and light in mouse models.
- Chan et al., 2022. Gamma frequency sensory stimulation in mild probable Alzheimer's dementia patients. PLOS ONE. Small human pilot studies using combined light and sound.
- Brain Beats: Do binaural beats actually work? The app's own plain-language summary of the evidence, with its safety notes.
This page is general information, not medical advice. Written by Matt Knapp, who runs a brain health program at a medical practice in Ellicott City, Maryland, and builds these apps on the side.
Try it with your ears.
Brain Beats is free, runs in your browser, and needs no account. Pick a state and press play.
Brain BeatsBrainwave sounds to focus or relax · brain-beats.com
More subjects: A moment to understand · All four apps: knapp.build/brain