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Ratings and global indices

Version 0.5 makes sessions reportable in three established idioms beyond the corpus's own descriptor set — HVAC/room criteria, environmental-noise descriptors, and soundscape-ecology indices — plus spatial descriptors only an ambisonic corpus can supply. Everything except the room criteria is appended automatically to the analyze summary and README table.

Room noise criteria (ventilation & building services)

from ambiscape import iso

spec = iso.background_octaves_db(F, pct=50, offset_db=cal["dbfs_to_dbspl"])
iso.room_criteria(spec)
# {'NR': 28.3, 'NR_governing_hz': 250, 'NC': 27.9, 'RC': 25.6,
#  'RC_class': 'R'}

NR (ISO/R 1996, analytic curves), NC (ANSI S12.2, tabulated), and a simplified RC (Blazier) with rumble/hiss classification — the language HVAC noise is specified in worldwide. Meaningful absolutely only with SPL calibration (calibration.json: dbfs_to_dbspl); uncalibrated ratings compare rooms recorded with one recorder+gain setup only. Compute them per machine state (states.state_segments masks) to rate "vent on" vs "vent off" separately.

Environmental-noise descriptors

  • Intermittency ratio IR (analysis.intermittency_ratio, Wunderli et al. 2016): the share of energy carried by events — near 0 for steady drones and dense traffic, high when energy arrives as distinct events. The single best complement to events/min.
  • Emergence LAeq − LA90: how far the energetic mean sits above the background — the classic "how eventful" number.

Ecoacoustic indices (ambiscape.ecology)

ACI, ADI/AEI, NDSI, BI, and acoustic entropy H — the standard soundscape-ecology battery, computed from the cached 96-band spectrogram. Reported for cross-corpus comparability; indoors, read NDSI/BI as "energy in the 2–8 kHz band", not as proof of biophony (a ventilation hiss scores as birds). Combine with the taxonomy layer before interpreting.

Spatial descriptors (ambiscape.spatial)

  • Directional entropy — how many directions the place sounds from (0 = one bearing, 1 = even around the horizon); the spatial analogue of a diversity index.
  • Horizon fractions — energy from above / around / below ±10° elevation: separates ceiling-mounted services and birds from footsteps and ground traffic.
  • Foreground/background azimuth overlap — Bhattacharyya overlap of the loudest-25 % and quietest-25 % direction histograms: 1 when figure and ground share a direction (one-source rooms), 0 when they occupy different sectors.

Room-acoustics companions

analysis.decay_metrics extends decay_time (unchanged, its numbers feed frozen reports) with EDT, C50/C80, and D50 per octave from the same truncated-Schroeder decay — reverberance and clarity from any good impulse in the recording.