Z zvuk
FX

Filter

Biquad filter as a bus FX insert. Lowpass for muffles, highpass for radios, bandpass for telephone, peaking for EQ.

TL;DR

A single BiquadFilterNode wrapped in the FX-insert contract. Pick a type, a frequency, a Q. Drive it from a Parameter for cinematic transitions.

API surface

Filter + FilterConfig ts 
class Filter implements FxInsert {
  readonly input: BiquadFilterNode;
  readonly output: BiquadFilterNode;
  bypassed: boolean;

  setType(t: FilterKind): void;
  setFrequency(hz: number): void;
  setQ(q: number): void;
  dispose(): void;
}

type FilterKind = 'lowpass' | 'highpass' | 'bandpass' | 'notch' | 'peaking' | 'allpass';

interface FilterConfig {
  type?: FilterKind;
  frequency?: number;                 // Hz
  q?: number;
  gain?: number;                      // dB — peaking only
}

Live demo

Type, frequency, Q. Try lowpass at 400 Hz with high Q for a wah.

Recipes

Insert + live tweak

ts ts 
import { Filter } from 'zvuk';

const fx = new Filter(engine.context, {
  type: 'lowpass',
  frequency: 800,
  q: 1.2,
});
engine.bus('music').addFx(fx);

// Live sweep
fx.setFrequency(2000);
fx.setQ(0.7);

"Underwater" sweep from a Parameter

ts ts 
// Sweep a filter from a Parameter for "underwater" / "muffled" effects.
const muffle = engine.parameter('muffle', 0);
muffle.bindTo((v) => fx.setFrequency(v), { from: 20000, to: 400, curve: 'easeIn' });

muffle.set(1);   // fully underwater

Common starting points

EffectTypeFrequencyQ
Muffled / underwaterlowpass400–800 Hz1
Tinny radio / phonebandpass1500 Hz2
Subwoofer cuthighpass120 Hz1
De-hisslowpass10 kHz0.7
Wahbandpassswept4–8

Pitfalls

Don't push Q to extremes.
Q above 10 starts ringing. On music, that's a feedback howl. Stay under 5 unless you're sweeping for a deliberate effect.

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