@audio/weighting-itu468

ITU-R BS.468-4 noise weighting — broadcast noise-measurement curve, peaked near 6.3 kHz

import itu468 from '@audio/weighting-itu468'

Time-domain ITU-R BS.468-4 weighting: exact matched-z realization of the analog prototype (6 poles — two complex pairs plus two real, one zero at DC — found via Durand-Kerner root-finding on the spec's rational polynomial, Rec. ITU-R BS.468-4 Annex 1). The analog prototype matches the spec's reference table to within 0.05 dB across 31.5 Hz–20 kHz; the discrete filter reproduces this near-exactly away from Nyquist (error grows above ~10 kHz at 44.1/48 kHz — use ≥96 kHz for closest match at the top octave). Peaks +12.2 dB near 6.3 kHz. 3 second-order sections, normalized to exactly 0 dB at 1 kHz.

itu468(data)                              // in place, fs=48000
itu468(data, { fs: 96000 })
let sos = itu468.coefs(96000)             // 3 SOS sections — feed digital-filter's freqz
itu468.response(6300, 48000)              // |H(6300)| — near the +12.2dB peak

Use when: measuring broadcast/telecom noise (hum, hiss, quantization noise) per ITU-R BS.468-4 / EBU Tech 3308 — weights toward the ear's peak sensitivity band rather than SPL-meter curves (A/B/C/D).

Part of @audio/weighting — the weighting family umbrella.

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