@audio/filter-resonator

import resonator from '@audio/filter-resonator'

Constant peak-gain bandpass — peak amplitude stays fixed regardless of bandwidth.

$H(z) = \dfrac{\frac{1-R^2}{2}(1 - z^{-2})}{1 - 2R\cos(\omega_0)z^{-1} + R^2 z^{-2}}$

Pole radius: $R = e^{-\pi \cdot bw / f_s}$ — controls bandwidth; $bw \to 0$ gives infinite Q
Peak gain: always 0 dB by construction — the two zeros at $z = \pm 1$ shape the numerator so $(1-R^2)/2$ normalizes the pole peak regardless of fc/bw (verified ±0.01 dB across fc ∈ {50, 440, 5000, 15000} Hz, bw ∈ {5, 20, 200} Hz)
Origin: Julius O. Smith III, Introduction to Digital Filters with Audio Applications — Two-Pole, "Constant Peak-Gain Resonator"

resonator(buffer, { fc: 440, bw: 20, fs: 44100 })

Pass the same params object on every call to persist the two-pole state across blocks. Internal cache fields are prefixed _r* (_rFc, _rA1, …) so params can double as a caller-owned object — e.g. @audio/speech-formant shares one params object per formant band.

Use when: additive synthesis (bells, gongs), modal synthesis, formant bank building.

vs Peaking EQ: resonator has fixed 0 dB peak; peaking EQ has variable gain — use resonator for synthesis, EQ for mixing.

Part of @audio/filter — the filter family umbrella. This README is generated from the umbrella docs.

MIT © audiojs