@audio/measure

Practical recording measurement — capture what your room/gear actually does.

Package	What
@audio/measure-ir	ESS sweep → impulse response (Farina 2000) — feeds reverb-convolution + amp-cabinet
@audio/measure-latency	loopback round-trip latency, sample-exact via FFT cross-correlation
@audio/measure-align	multi-mic delay + polarity alignment, optional correction apply
@audio/measure-response	frequency response of a device/chain from its impulse response
@audio/quality	objective SNR/LSD/spectral-similarity metrics vs. a reference signal

import { ir, latency, align, response, snr, lsd } from '@audio/measure'
import chirp from '@audio/synth-chirp'

let sweep = chirp({ f0: 20, f1: 20000, duration: 1.5, fs })
let h = ir(recorded, { sweep, f0: 20, f1: 20000, fs, length: 1000 })       // impulse response
let { freqs, db } = response(h, { fs, n: 8192 })                          // frequency response

let lat = latency(recorded, reference, { fs })                            // { samples, seconds, confidence }
let al = align(a, b, { fs, apply: true })                                 // { delay, seconds, polarity, aligned? }

snr(clean, processed)   // dB; lsd(a, b) — log-spectral distance, dB

ir(recorded, {sweep, f0=20, f1, fs=44100, length}) → Float32Array — Farina exponential-sine-sweep deconvolution: inverse filter = time-reversed sweep with exp(−t/L) compensation, distortion products land at negative time and are trimmed. Self-deconvolution calibrated so an identity system yields δ = 1.0.

latency(recorded, reference, {fs=44100}) → {samples, seconds, confidence} — FFT cross-correlation peak.

align(a, b, {fs=44100, apply=false}) → {delay, seconds, polarity: 1|-1, aligned?} — signed cross-correlation peak gives delay + polarity of b relative to a; apply: true shifts/flips b.

response(ir, {fs=44100, n=8192}) → {freqs, db} — zero-padded FFT magnitude.

@audio/quality exports snr, segSnr, lsd, spectralSim, nrr, speechAttenuation, goertzelEnergy, chordBalance, chordRetention, modulationDepth — reference-vs-output metrics for evaluating denoisers, stretchers, codecs, resamplers (see packages/quality/README.md). The Goertzel-family functions (goertzelEnergy etc.) take a positional sample rate.

Sweep generation = @audio/synth-chirp; deconvolution = inverse-sweep convolution via fourier-transform FFT. The practical-VST/recording surface: measure once, convolve forever.