Echo

Adds a delayed, fading repeat of the signal: a feedback echo (simple delay line). Each repeat is quieter than the previous by the feedback factor, producing a natural decay tail. The mix prop controls the wet/dry blend.

Usage

import { Sound, AudioFilters } from '@motion-script/core';

// Via AudioFilters builder — 300 ms delay, 40% feedback, default 50% wet mix
const clip = new Sound({ src: './voice.mp3', filters: AudioFilters.echo({ delay: 0.3, feedback: 0.4 }) });

// With explicit mix — mostly dry, subtle echo
const clip = new Sound({ src: './voice.mp3', filters: AudioFilters.echo({ delay: 0.5, feedback: 0.6, mix: 0.25 }) });

// Via raw object
const clip = new Sound({
  src: './voice.mp3',
  filters: [{ type: 'echo', delay: 0.3, feedback: 0.4, mix: 0.5 }],
});

Props

Prop	Type	Default	Description
`type`	`'echo'`	–	Filter identifier
`delay`	`number`	–	Time before the first repeat, in seconds
`feedback`	`number`	–	Repeat decay factor, `0`–`<1`. Each echo is this fraction of the previous
`mix`	`number`	`0.5`	Wet/dry blend. `0` = dry signal only, `1` = fully wet (no original)

Animating

Fade the echo in to add spaciousness over time:

import { Sound, AudioFilters, tween, lerpNumber, easeOut } from '@motion-script/core';

const clip = new Sound({ src: './narration.mp3', filters: AudioFilters.echo({ delay: 0.4, feedback: 0.5, mix: 0 }) });
clip.start();

// Crossfade to a wet echo over 3 seconds
yield* tween(3, (t) => {
  clip.set({ filters: AudioFilters.echo({ delay: 0.4, feedback: 0.5, mix: lerpNumber(0, 0.6, easeOut(t)) }) });
});

Stacking with other filters

// Muffle the echo tails with a low-pass
AudioFilters.echo({ delay: 0.3, feedback: 0.5 }).lowpass(3000)

// Quieter source into a long, washy reverb-like echo
AudioFilters.gain(0.7).echo({ delay: 0.6, feedback: 0.75, mix: 0.4 })

Notes

feedback must be strictly less than 1. A value of 1 or above creates an infinite loop that never decays.
Long delay values (> 1s) with high feedback (> 0.7) can cause the tail to accumulate loudly. Preview with low mix first.
All three props (delay, feedback, mix) are fully animatable.