Two sine waves, one per ear, slightly detuned. Your left ear gets 200 Hz, your right gets 210 Hz. The 10 Hz difference isn't in the audio — your brain synthesizes it as a perceived amplitude wobble at the beat frequency.
This is pure acoustic interference. No modulation, no processing. The "beat" is an auditory illusion that only exists inside your head, which is why headphones are required.
Delta (1–4 Hz) — deep sleep, unconscious processing.
Theta (4–8 Hz) — drowsy, meditative, hypnagogic.
Alpha (8–13 Hz) — relaxed, calm focus. The default.
Beta (13–30 Hz) — active thinking, alertness.
Gamma (30–50 Hz) — high-level cognition, binding.
Same binaural principle, but each ear also gets an overtone — a second sine wave at a harmonic multiple of the fundamental. The beat still emerges from the fundamental pair. The overtone just makes the tone warmer and more musical.
Octave (2x) — one octave up. Clean, open.
Fifth (1.5x) — a perfect fifth. Warm, slightly complex.
Octave + Fifth (3x) — the twelfth. Bright and resonant.
Two Octaves (4x) — two octaves up. Airy, shimmering.
The overtone mix slider controls the volume of the overtone relative to the fundamental. At 0% it's pure binaural. At 100% the overtone is equal volume.
The auditory barber pole. Seven sine waves spaced one octave apart, all gliding upward (or downward) simultaneously. A Gaussian spectral envelope fades each tone in as it enters the low end and out as it exits the high end. The result: an endlessly rising pitch that never actually gets higher.
It's a real psychoacoustic illusion — the pitch is always moving but never arrives. Works well as a focus texture because it creates constant forward motion without resolution.
The speed control sets how many seconds each tone takes to traverse one octave. Slower = more meditative. Faster = more tension.
White noise fed through a bank of narrow bandpass filters, each tuned to a harmonic of a chosen fundamental frequency. What comes out is noise that has pitch — a breathy, organ-like drone.
Fundamental — the base pitch. 100 Hz is a low drone. 200 Hz is warmer. Lower = more ominous.
Resonance (Q) — how narrow the filters are. Low Q = more noise bleeds through, breathy and diffuse. High Q = tighter pitch, more tonal, almost organ-like.
Harmonics — how many overtones. 2–3 sounds hollow. 8+ sounds full and rich. 16 starts to approximate a sawtooth timbre filtered through noise.
The 1/h amplitude rolloff gives each harmonic progressively less energy, mimicking the natural harmonic series of acoustic instruments.
All noise is random, but the spectral distribution makes them sound very different.
White — equal energy at all frequencies. Bright, hissy. Like TV static or a waterfall up close.
Pink (1/f) — energy drops 3 dB per octave. Sounds more balanced to human ears because we perceive octaves logarithmically. Like steady rain.
Brown (1/f²) — energy drops 6 dB per octave. Deep, rumbly. Like distant thunder or a jet cabin. Named for Brownian motion, not the color.
Web Audio API oscillators get suspended when the browser tab is hidden or the phone screen locks. The workaround: all audio is routed through a MediaStreamDestination connected to a hidden <audio> element. The OS treats this as media playback and keeps it alive.
The audio goes exclusively through the <audio> element — no dual output to ctx.destination. This prevents clipping when the browser throttles the AudioContext on tab switch.