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Geophony

The non-biological, non-human ground of a soundscape: wind, rain, and water. geophony reads the cached features (no audio pass) for two structures, and its descriptors ride in the analyze summary.

What it measures

  • Wind — low-frequency (below ~200 Hz) energy that is diffuse and non-directional. Wind on the capsules is incoherent between channels, so ambisonic diffuseness rises; geo_wind_index is the low-band energy weighted by median diffuseness (it falls back to plain low-band energy for stereo/mono, which cannot resolve diffuseness).
  • Rain / water — broadband high-frequency hiss that is spectrally flat and temporally steady (a shower, a fountain, a stream); geo_rain_index is the 2–16 kHz energy fraction times median spectral flatness.
  • geo_lowfreq_fraction / geo_highband_fraction — the underlying band shares; geophony_index is the larger of wind and rain.

Usage

ambiscape analyze <session>     # geo_* keys appear in the summary
ambiscape geophony <session>    # detail: writes geophony.json

from ambiscape import features, geophony
F = features.load_features(sorted((out / "features").glob("*.npz")))
geophony.summarize_geophony(F)

Caveats

Proxies, not detection. Wind and HVAC rumble share the low band (a train's rumble reads partly as wind); rain, applause, and frying share the flat high-band hiss. Diffuseness disambiguates wind only for ambisonic input. Treat the indices as candidates to confirm by ear.