BiquadFilterNode shapes the frequency content of any audio signal. Change the type, cutoff frequency, and resonance to sculpt tone from a flat noise source.
Filter explorer
The source is white noise — it contains all frequencies equally, so the filter response is exactly what you hear. The blue curve shows the frequency response: how much of each frequency gets through.
20 Hz1005001 k5 k20 kHz
1000 Hz
Q 1.0
+6 dB
Filter types
Each type applies a different transfer function. Lowpass and highpass are the workhorses — bandpass isolates a frequency band (useful for formant synthesis), notch removes a narrow band (60 Hz hum), peaking and shelf filters are equaliser tools.
Q factor (resonance) controls how sharply the filter acts around the cutoff. A high Q creates a resonant peak at the cutoff — the filter "rings". At extreme Q values a lowpass filter self-oscillates, producing a sine wave at the cutoff frequency with no input signal.
Frequency is logarithmic. The slider uses a log scale because musical intervals are multiplicative. An octave is always a 2× frequency ratio — 100–200 Hz, 200–400 Hz, 1–2 kHz all span one octave.