Estimated distance to source for propagation model
SPATIAL BEARING MAP
SOURCE BEARINGS (γ² ≥ 0.5)
Waiting for data...
SKY VIEW — BEARING × ELEVATION (PREP)
No elevation data yet
This panel is reserved for sky-view data: each point is one frequency band's source direction in (bearing, elevation). To populate it, mount at least one mic at a meaningfully different height (vertical baseline) and enable an elevation-TDOA pass in sentinel. The grid below is the canvas it will fill.
Densitylowhigh
Hover the plot for band/source detail
LOCKED SOURCES
No locked sources yet. Click LOCK IN FROM CURRENT WINDOW to capture dominant bearing clusters and their spectral fingerprints from whatever's in the heat map right now. Locked sources persist locally (localStorage) and will be matched by fingerprint against future elevation passes.
HOW TO READ THIS MAP
This map uses two microphones separated by a known distance to determine the direction of noise sources at each frequency band. Each colored line is a bearing — a compass direction the noise is coming from at that frequency.
Coherence (γ²)
Measures how synchronized the pressure waves are between the two microphones at each frequency. Think of it like two people watching ocean waves from different spots on the shore:
γ² ≈ 1.0 — Both see the exact same wave pattern arriving in lockstep. That's a real, identifiable source — a machine, a fan, a compressor.
γ² ≈ 0.0 — Each mic hears completely different, random noise. No identifiable source — just wind, traffic, general ambient.
γ² ≥ 0.7 — High confidence: mechanical source confirmed at this frequency.
Only frequencies with significant coherence produce reliable bearing lines. Low-coherence frequencies are noise, not signal.
TDOA (Time Difference of Arrival)
The time delay between when a sound wave reaches mic 1 versus mic 2. This delay maps directly to a compass bearing:
Sound from the left of the array arrives at the left mic first → positive delay.
Sound from directly ahead (broadside) arrives at both mics simultaneously → zero delay.
The delay is converted to an angle using: θ = arccos(Δt × speed_of_sound / mic_separation).
A two-mic array has front/back ambiguity — it can't distinguish sounds from above vs below the array axis. The "Disambiguate" control resolves this using level differences or forced quadrant selection.
What the Lines Mean
Red/orange lines — VFD motor harmonics (66, 132, 198, 264, 330, 396 Hz). These are the frequencies generated by variable-frequency-drive HVAC fans.
Blue lines — Other coherent frequencies (broadband mechanical noise, structural resonances).
Wider wedge = lower coherence = less certain direction.
Narrow wedge = high coherence = confident bearing.
Heat map (colored wedges on map) — Accumulated bearing density over time. Brighter/warmer colors = more epochs with sources in that direction. Persistent sources glow; transients fade.
Noise contours (when enabled) — Projected sound levels at various distances from the estimated source. Uses hemispherical propagation model. Red = louder, blue = quieter.
Epoch counter — Number of 30-second measurement cycles contributing to the heat map.
Key insight: When multiple independent frequency bands — each measured with high coherence — all point to the same compass bearing, this constitutes strong evidence that a specific mechanical source at that location is responsible. The probability of unrelated noise sources at different frequencies coincidentally producing the same bearing is negligible.