Stereo beat frequencies, reference tones, and synthesized patterns, generated in the browser with the Web Audio API. Beats need stereo headphones.
What this plays
Binaural beats
Each ear receives one sine tone. The right-ear tone is higher by the beat frequency. Over headphones the two tones are combined in the auditory system and a fluctuation at the difference frequency is perceived. Over speakers the tones mix in the air instead and the result is an ordinary acoustic beat.
Band names
Beat frequencies are tagged with the EEG band whose range contains them: delta 0.5–4 Hz, theta 4–8 Hz, alpha 8–12 Hz, beta 12–30 Hz, gamma 30–100 Hz. Boundaries vary between sources. The tag describes the number, not an effect.
Pure tones
Single sine oscillators. The solfeggio values (396, 417, 528, 639, 741, 852 Hz, later extended with 174 and 963 Hz) were published by Puleo and Horowitz in 1999 from a numerological reading of Numbers 7:12–83. They are not derived from a tuning system, and there is no controlled evidence of a physiological effect specific to them. 440 Hz is ISO 16 concert pitch; 432 Hz is an alternative concert pitch.
Generated patterns
Multi-oscillator and looped-buffer synthesis. Each entry's description states the algorithm and its constants.
Listening
Use headphones for beats.
Keep the volume low. The output compressor limits peaks; it does not make loud listening safe.
Stop if anything is uncomfortable. This is an audio tool, not a treatment.
Up to six entries play at once; starting a seventh stops the oldest.
Source
github.com/1ps0/binaural. Single-file build with no network requests; save the page and open it from disk in any current browser.