Wear headphones. A binaural beat is not in the sound, it is in the difference between your ears: one tone goes left, a slightly higher one goes right, and the pulse you hear is made by your own hearing. On speakers the two tones mix in the air and the effect is gone.

Sound

Delta 0.5 - 4 Hz · deep sleep

The slowest rhythm, dominant in dreamless sleep and in the first months of life. Associated with physical restoration and the release of growth hormone.

Theta 4 - 8 Hz · drowsiness and deep meditation

The border between waking and sleep: hypnagogic imagery, deep meditation, REM sleep, and the loose associative thinking that often precedes an idea.

7.83 Hz is the Earth's own background resonance - too low for a speaker to reproduce, but perfectly playable as a beat.

Alpha 8 - 13 Hz · relaxed wakefulness

The rhythm that appears when you close your eyes and stop working at anything. Calm, receptive, awake. The first brainwave ever recorded, by Hans Berger in 1924.

Beta 13 - 30 Hz · alert and focused

Ordinary waking attention: reading, talking, solving a problem. Low beta is steady focus; high beta shades into alertness and, past a point, anxiety.

Gamma 30 - 100 Hz · peak concentration

The fastest band, linked to binding separate perceptions into one experience, and to moments of insight. Hardest to entrain, and the most debated.

Custom

The beat is the difference between your ears, and the band it falls in. The carrier is the pitch you actually hear - the beat is easiest to perceive with a carrier between 100 and 400 Hz.

While a session is playing, moving either slider glides the tones to the new setting instead of restarting them.

About binaural beats

Heinrich Wilhelm Dove described the effect in 1839: two tones close in pitch, one per ear, and the brainstem reports a third pulse at their difference. The modern claim, called brainwave entrainment, is that sustained exposure nudges cortical rhythm toward that difference.

The honest summary of the research: studies most consistently report modest effects on anxiety, relaxation, and subjective sleep quality. Results for memory and attention are mixed, sample sizes are usually small, and it is hard to tell the beat apart from the simple act of sitting still with headphones on for twenty minutes. Treat it as a pleasant timer for doing nothing, and anything more is a bonus.

If you have epilepsy or a seizure disorder, are wearing a pacemaker, or are pregnant, ask a doctor before using brainwave entrainment. Do not listen while driving.