order op• Data kinds: signal → table
• Call: import fullseye as fs; fs.ledger.angular_resample(x, rate, rpm, samples_per_rev=64) (to call the implementation directly, import acoustics; acoustics.angular_resample(x, rate, rpm, samples_per_rev=64); from the registry, opsacoustics.get("angular_resample"))
Resample a time record onto the shaft-angle axis (computed order tracking).
Under a changing shaft speed, a component locked to the shaft has a moving frequency and smears across the spectrum, while a structural resonance stays put. Resample the record so the samples are equally spaced in shaft angle instead of in time and the situation reverses exactly: the order becomes a single line and the resonance smears.
rpm is either a single number (constant speed — the transform is then a pure rescaling) or a per-sample array on the same clock as the signal. The cumulative revolution count is the trapezoidal integral of rpm/60, and the signal is linearly interpolated onto a uniform grid in it.
Returns a dict — an angle-domain record is not put into circulation as a plain signal, deliberately. Its samples are indexed by angle, not time, so handing it to any op that takes a rate would produce frequencies in Hz from an axis measured in revolutions: no exception, no NaN, just wrong numbers. (Same judgement, and the same reason, as motionmag.motion_magnify not exposing a bare video adapter.) The dict carries signal, angle_rev, samples_per_rev, revolutions (total), whole_revolutions, rate (the original time-domain one, for provenance), mean_rpm, max_order.
max_order is samples_per_rev / 2 — the Nyquist of the *angle* axis.
Measured: a pure order-3.5 component on a 600 -> 1800 rpm ramp, resampled at 64 samples/rev over 78 whole revolutions, reads amplitude 0.999371 in a single bin of the order spectrum; the same component in the ordinary spectrum peaks at 0.070203 and is 66.5 Hz wide.
Raises ValueError: everything _as_signal refuses, a non-positive or wrong-length rpm, samples_per_rev outside [2, 65536], an output over MAX_ANGULAR_SAMPLES, fewer than one complete revolution in the record, and — the aliasing refusal — a samples_per_rev whose implied Nyquist order needs content above the time-domain Nyquist. Asking for 64 samples/rev on a shaft turning at 30 Hz means representing 960 Hz, which a 100 Hz recording does not contain; the resampler would happily manufacture it from the interpolation.
• acoustic_condition_monitoring family guide
• Sample-data catalog (download URLs / licences) — 2-D uses skimage.data (BSD/public domain) plus synthetic images; 3-D lists download URLs for real data sources (Stanford, PDS, …).
• Operator provenance and references — the sources of the research/methods this op family came from.
• The canonical algorithm (author, year) and its uses are named in the family usage guide above.
• acoustic_condition_monitoring — py -3.11 examples/acoustic_condition_monitoring.py
table as input)order)*Provenance: acoustics.py — ACOUSTICS operator registry. This per-op note is generated by tools/opdocs.py md (do not hand-edit).*
© 2026 Kazufumi Furuse — Fullseye operator documentation. Licensed under Apache-2.0.