Generate binaural beats by playing a slightly different tone in each ear. Pick a brainwave band or set the frequencies yourself. Use headphones.
Binaural beats only work with headphones: each ear hears a slightly different frequency and the brain perceives the difference as a pulsing beat. This is a relaxation and focus aid, not a medical treatment. Generated live in your browser; nothing is recorded.
When each ear hears a slightly different pure tone (say 200 Hz and 210 Hz), the brain perceives a third, pulsing tone at the difference (10 Hz). That perceived pulse is the binaural beat. It only happens with headphones, because each ear must hear only its own tone.
The presets map the beat frequency to EEG bands often associated with mental states: delta with deep sleep, theta with meditation, alpha with relaxed focus, beta with alertness and gamma with concentration. Pick a band or set the carrier and beat yourself.
Evidence is mixed and effects are subtle and individual. Treat them as a relaxation or focus aid to experiment with, not a medical treatment. Keep the volume comfortable.