LowPassFilter

A low-pass audio filter that attenuates frequencies above a cutoff point.

Low-pass filters allow low frequencies to pass through while reducing or eliminating high frequencies. Common uses include:

• Removing high-frequency noise or hiss
• Creating "muffled" or "underwater" effects
• Simulating sounds heard through walls
• Smoothing harsh digital audio
• Bass isolation for subwoofer systems

The filter uses a biquad implementation for stable, efficient processing with adjustable resonance (Q factor) for frequency emphasis at the cutoff.

// Remove high frequencies above 2000Hz
var lowPass = new LowPassFilter();
lowPass.cutoffFrequency = 2000;
lowPass.gain = 1.0;

// Create a resonant low-pass sweep effect
var sweepFilter = new LowPassFilter();
sweepFilter.resonance = 8.0;  // High resonance for dramatic effect
app.onUpdate(this, delta -> {
    // Sweep cutoff from 200Hz to 5000Hz
    sweepFilter.cutoffFrequency = 200 + (Math.sin(Timer.now) + 1) * 2400;
});

// Apply to an audio mixer
audioMixer.addFilter(lowPass);

Instance Members #

Cutoff frequency in Hz. Frequencies above this value will be attenuated. Range: 1 Hz to half the sample rate (Nyquist frequency). Default: 1000 Hz

Filter gain/amplitude multiplier. Adjusts the overall output level after filtering. Range: 0.0 to any positive value (1.0 = unity gain). Default: 1.0

Filter resonance/Q factor. Controls the sharpness of the filter and frequency emphasis at the cutoff.

• 0.707: No resonance (Butterworth response, flat passband)
• < 0.707: Gentler rolloff
• > 0.707: Sharper rolloff with peak at cutoff
• High values (5-30): Creates strong resonant peak (self-oscillation) Range: 0.1 to 30.0 (higher values = more resonance) Default: 0.707

Metadata #