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Cross-session comparison

The catalog answers how do my places differ; compare answers how did this place differ between visits — two or more analysed sessions of one room laid onto a common clock, so machines, weather, parties and silences read against each other. It works entirely from the cached 1 Hz features and the summary.json / states.json of a prior analyze run; no audio is reopened.

ambiscape compare 2026-07-15-loft 2026-07-19-loft-night 2026-07-19-loft-day \
    --lines 146,258,650,820 --band 2000:8000 --hours 27:34
#   ... LAeq per session, tonal-line prominence per session ...
#   wrote .../comparisons/<names>/compare.json and 4 figure(s)

What it produces

Always:

  • Clock-aligned LAeq timelines — per-minute level on a shared hour-of-day axis. Sessions whose spans bridge (a night flowing into the next morning) share a row and line up end to end; separate visits get their own rows. The --state intervals are shaded.
  • Per-state LTAS overlay — median band spectra split by each session's detected states, so a machine's broadband signature (or its absence) is visible at a glance.
  • Azimuth roses — foreground energy by azimuth, one panel per session (mic frames usually differ between visits: compare shapes, not bearings).
  • Descriptor tables — pooled and state-resolved, in compare.json.

Optional:

  • --lines A,B,C — tonal-line prominence per session: how far each named frequency (a machine fingerprint) stands out of the per-minute minimum spectrum. A machine that ran keeps several dB; one that never ran, ≲ 1 dB.
  • --band F0:F1 [--hours H0:H1] — a band timeline on the clock axis (2–8 kHz for a dawn chorus or rain hiss, 100–300 Hz for party bass), optionally restricted to a clock window (hours > 24 = day 2).

Programmatic helpers

ambiscape.compare also exposes the pieces directly: load_comparison, laeq_timeline, clock_rows, ltas_by_state, line_prominence, band_level, floor_difference (a near-floor source detector — a quiet fan's band shelf that never reaches a level step), and duty_cycle (period, duty and regularity of a cycling source such as a fridge, and its absence from a new mic position). See the API reference.