Neural Harmonica

Science notes — binaural vs isochronic vs phase-coherent multimodal entrainment
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What “Neural Harmonica” adds (in plain science terms)

A neural harmonica is not a new biological mechanism by itself—it's a signal design strategy: you generate audio and visual stimulation so they share a single timing reference (phase origin), then you keep them aligned with harmonic sampling (frame rate as an integer multiple of the entrainment frequency) and calibration markers.

Audio starts at defined phase (cosine)
Video FPS is beat × N (harmonic)
Brightness is sinusoidal and phase-locked
Motion is deterministic and beat-aligned
Calibration enables device-level sync

Underlying science (what you can defend)

Entrainment is about rhythmic sensitivity

Neural systems show frequency-specific responsiveness: periodic sensory input can bias the timing of ongoing neural activity. In practice, measured effects vary by person, context, stimulation intensity, and whether the stimulus is actually perceived cleanly.

Phase matters if you are stacking layers

When two rhythmic streams are combined (audio + visual + motion), inconsistent phase relationships create competing cues. A phase-coherent design reduces internal “jitter” so the strongest cue is consistent across modalities.

Harmonic sampling prevents drift

If the frame rate is an integer multiple of the target rhythm, each cycle is sampled at the same points every time. That avoids frame-by-frame phase walk (a common source of unintended modulation artifacts).

Calibration is required for real devices

Playback pipelines buffer audio/video differently. A frame-0 flash plus an audio tick lets you measure the latency offset and compensate, turning “file-level alignment” into “device-level alignment.”

Comparison 1: Neural Harmonica vs Binaural beats

Binaural beats (what they are)

Binaural beats occur when each ear receives a pure tone at slightly different frequencies. The auditory system can produce a percept related to the difference frequency (the “beat”). Headphones are typically required.

L(t) = cos(2π fL t) R(t) = cos(2π fR t) beat = |fR − fL|

Strengths

  • Low visual load (audio-only).
  • Simple to generate and distribute.

Limitations (practical, not ideology)

  • Beat is a perceptual/central phenomenon, not a literal amplitude pulse in the air signal.
  • Effect size depends on listener, attention, hearing, and playback conditions.
  • Adding extra modulation layers without phase design can create competing cues.

What Neural Harmonica changes relative to binaural

  • Defines a shared phase origin across modalities (audio + visual + motion), not just audio.
  • Uses harmonic FPS and calibration markers to preserve alignment through real playback stacks.
  • Adds an explicit visual entrainment envelope (sinusoidal luminance) that can be phase-locked to audio onset.

Comparison 2: Neural Harmonica vs Isochronic tones

Isochronic tones (what they are)

Isochronic tones are typically a carrier tone whose amplitude is pulsed on/off (or smoothly gated) at a target frequency. Unlike binaural, the beat is explicitly present in the waveform as amplitude modulation.

carrier(t) = sin(2π fc t) pulse(t) = gate(beat) iso(t) = carrier(t) × pulse(t)

Strengths

  • Clear rhythmic cue; does not require headphones.
  • Easier for many users to perceive as “pulsing.”

Limitations

  • Hard gating can introduce clicks and listening fatigue.
  • Strong amplitude modulation can mask subtler features (including binaural perception if mixed improperly).
  • Without phase discipline, layering with visuals can still drift or compete.

What Neural Harmonica changes relative to isochronic

  • Doesn’t require hard pulses; uses a sinusoidal luminance envelope and can keep audio smooth (cosine-phase pure tones).
  • Mandates a spatial motion cycle that is beat-aligned, adding a distinct synchronized cue channel.
  • Adds calibration so A/V phase remains correct on the actual playback device.

Why the calibration header matters (research-grade)

Even if your audio and video are mathematically aligned in the file, phones/PCs/TVs may output them at different times due to buffering and processing. Neural Harmonica’s flash+tick header creates a measurable offset:

  • Visual marker: frame 0 full-screen flash with timecode
  • Audio marker: impulse tick at sample 0

Record playback, measure flash vs tick timing, then compensate (delay audio or video) to restore true device-level synchronization.

Safety note

Strong flicker can trigger adverse effects in sensitive individuals (including photosensitive epilepsy). Treat high-frequency luminance modulation with caution, and avoid using if you have a known sensitivity. Use lower brightness and consult appropriate guidance when in doubt.