MotionScript

Low-Pass

Attenuates frequencies above the cutoff, letting the lows through. Use it to muffle audio, simulate sound heard through a wall or underwater, or soften a harsh mix.

Usage

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

// Via AudioFilters builder — muffle everything above 1000 Hz
const clip = new Sound({ src: './music.mp3', filters: AudioFilters.lowpass(1000) });

// With resonance boost at the cutoff
const clip = new Sound({ src: './music.mp3', filters: AudioFilters.lowpass({ frequency: 800, q: 3 }) });

// Via raw object
const clip = new Sound({ src: './music.mp3', filters: [{ type: 'lowpass', frequency: 1000 }] });

Props

PropTypeDefaultDescription
type'lowpass'–Filter identifier
frequencynumber–Cutoff frequency in Hz. Content above this is rolled off
qnumber1Resonance (Q factor) at the cutoff. Higher values add a peak just before the roll-off

Animating

Animate the cutoff to smoothly muffle audio over time. This is a common technique for scene transitions:

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

const clip = new Sound({ src: './ambient.mp3', filters: AudioFilters.lowpass(20000) });
clip.start();

// Muffle the audio as the scene fades out
yield* tween(2, (t) => {
  clip.set({ filters: AudioFilters.lowpass(lerpNumber(20000, 400, easeIn(t))) });
});

Notes

  • 20000 Hz is effectively unfiltered for most audio content, so use it as a "pass-through" starting value when animating.
  • Pair with a high-pass filter to isolate a frequency band: AudioFilters.highpass(200).lowpass(3000).
  • Both frequency and q are fully animatable.