Brain waves: the five rhythms
Your brain’s electrical activity rises and falls in rhythms that change with sleep, rest and focus. Here they are side by side, at their real speeds.
Five rhythms, drawn to speed
8–13 Hz · Relaxed wakefulness, eyes closed
Slower waves are larger because big populations of neurons fire in step; faster rhythms are smaller and more local. On a real EEG the trace is a mixture of all bands at once, and a "state" just means one band dominates.
Alpha waves in depth| Band | Range | Typical state | Play |
|---|---|---|---|
| Delta waves | 0.5–4 Hz | Deep, dreamless sleep | 2 Hz beat |
| Theta waves | 4–8 Hz | Drowsiness, light sleep, deep meditation | 6 Hz beat |
| Alpha waves | 8–13 Hz | Relaxed wakefulness, eyes closed | 10 Hz beat |
| Beta waves | 13–30 Hz | Active thinking and alertness | 16 Hz beat |
| Gamma waves | 30–100 Hz | Binding information together | 40 Hz beat |
How brain waves are measured
Electroencephalography (EEG) records tiny voltage changes, a few millionths of a volt, through electrodes on the scalp. Hans Berger made the first human recording in 1924 and published it in 1929; the alpha rhythm he saw is sometimes still called the "Berger rhythm". Any single electrode picks up a blend of all the bands at once. Saying someone is "in theta" means theta is unusually strong, not that other rhythms have stopped.
Can you change them with sound?
Partly. A sound that pulses steadily evokes a matching response in the auditory cortex, the auditory steady-state response, and it is strongest around 40 Hz. That is real, measurable and used in hearing tests. The popular leap, that a 6 Hz beat will put your whole brain into a theta state, is where evidence runs thin. Binaural beats and isochronic tones are the two common ways to try it.
Questions people ask
What are brain waves?
Rhythmic electrical activity produced when large groups of neurons fire in sync, recorded from the scalp with EEG. They are grouped by speed into delta, theta, alpha, beta and gamma.
What are the 5 types of brain waves?
Delta (0.5–4 Hz), theta (4–8 Hz), alpha (8–13 Hz), beta (13–30 Hz) and gamma (above 30 Hz). Exact boundaries vary slightly between textbooks.
Can sound change your brain waves?
Steady pulsing sound produces a measurable “steady-state” response in the EEG, especially near 40 Hz. Whether that shifts your overall state (making you sleepier or more focused) is not established.