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Soundwalks (walk mode)

A walking recording breaks the toolbox's core assumption — one microphone, one place, one soundscape whose statistics converge with time. On a soundwalk the non-stationarity is the signal, so walk inverts the pipeline: segment the recording into sub-soundscape zones first, then describe each zone as a short stationary session, the way ISO/TS 12913-2 soundwalks treat their stop points.

Usage

ambiscape analyze WALK/                     # cache features first
ambiscape walk WALK/                        # zones, cadence, regimes
ambiscape walk WALK/ --gps track.gpx        # + distance, speed, route map

Outputs land in WALK/analysis/: walk.md (the zone table), walk_zones.tsv (one row per zone), route_profile.png (spectrogram, level, cadence and diffuseness strips with zone boundaries), and — with a track — route_map.png (the route coloured by zone).

What it computes

  • Zones from multivariate change-point detection on the cached 1 Hz features (ambiscape.segmentation): Foote novelty over log-octave powers, log-centroid, log-flatness and diffuseness, on physical dB-like scales with an absolute contrast floor (--threshold-db, default 4). Transitions on a walk are gradients; read boundaries as centres of transition zones.
  • Per-zone descriptors: Leq, L10−L90, band fractions, flatness, centroid, diffuseness, event rate — each zone treated as a short stationary session.
  • Step cadence from the 50 Hz envelope: steps_per_min is a walking-speed proxy, step_salience says how much of the zone's foreground is the walker's own feet.
  • A figure–ground regime per zone: own-steps (the gait owns the foreground), external-events (things keep emerging), bed-only (nothing does), mixed.
  • Self-noise gating: footfalls (envelope impulses, dilated) and wind (per-second low-band × diffuseness gusts) are masked out of a gated level. Zones with clear gait report leq_gated_dbfs — what the place sounds like without the walker — plus step_time_fraction and wind_time_fraction. On the reference walk the walking group was 2–4 dB of its own quiet zones.
  • GPS (--gps track.gpx): GPX track points give each zone a distance, mean speed and midpoint position; track speed is an independent cross-check on the acoustic cadence. --gps-offset shifts session time when recorder and tracker do not share a clock (calibration.json clock_offset_s is applied to the session already).

Session-level honesty

analyze itself now diagnoses non-stationarity: a session whose features hold several regimes says so in its README, because session-level descriptors average over different places. Ecoacoustic indices (ACI, NDSI, ADI) assume a fixed sensor and are not meaningful for a walk; between-zone comparisons within one walk and one rig are the defensible use of everything here.

Companions

ambiscape draft proposes keynote beds per spectral regime (so a walk drafts one bed per sub-soundscape, not per level band) and ambiscape taxonomy renders the Schafer timeline — the natural sequence view of a walk — and the Schaeffer map, whose detected events inherit any named annotation spans that cover them.

Design notes and literature grounding live in the wiki's Soundwalk-Mode page; the reference case is a 12.8-minute walk across the Blindern campus (MUS2640, 2026-08-24).