BiquadFilterNode

The BiquadFilterNode interface represents a low-order filter. It is an AudioNode used for tone controls, graphic equalizers, and other audio effects. Multiple BiquadFilterNode instances can be combined to create more complex filtering chains.

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AudioNode properties

Number of inputs	1
Number of outputs	1
Channel count	2
Channel count mode	max
Channel interpretation	speakers

Constructor

BaseAudioContext.createBiquadFilter()

Properties

It inherits all properties from AudioNode.

Name	Type	Rate	Description
frequency	AudioParam	k-rate	The filter’s cutoff or center frequency in hertz (Hz).
detune	AudioParam	k-rate	Amount by which the frequency is detuned in cents.
Q	AudioParam	k-rate	The filter’s Q factor (quality factor).
gain	AudioParam	k-rate	Gain applied by specific filter types, in decibels (dB).
type	BiquadFilterType	—	Defines the kind of filtering algorithm the node applies (e.g. "lowpass", "highpass").

BiquadFilterType enumeration description

Note: The detune parameter behaves the same way for all filter types, so it is not repeated below.

type	Description	frequency	Q	gain
lowpass	Second-order resonant lowpass filter with 12dB/octave rolloff. Frequencies below the cutoff pass through; higher frequencies are attenuated.	The cutoff frequency.	Determines how peaked the frequency is around the cutoff. Higher values result in a sharper peak.	Not used
highpass	Second-order resonant highpass filter with 12dB/octave rolloff. Frequencies above the cutoff pass through; lower frequencies are attenuated.	The cutoff frequency.	Determines how peaked the frequency is around the cutoff. Higher values result in a sharper peak.	Not used
bandpass	Second-order bandpass filter. Frequencies within a given range pass through; others are attenuated.	The center of the frequency band.	Controls the bandwidth. Higher values result in a narrower band.	Not used
lowshelf	Second-order lowshelf filter. Frequencies below the cutoff are boosted or attenuated; others remain unchanged.	The upper limit of the frequencies where the boost (or attenuation) is applied.	Not used	The boost (in dB) to be applied. Negative values attenuate the frequencies.
highshelf	Second-order highshelf filter. Frequencies above the cutoff are boosted or attenuated; others remain unchanged.	The lower limit of the frequencies where the boost (or attenuation) is applied.	Not used	The boost (in dB) to be applied. Negative values attenuate the frequencies.
peaking	Frequencies around a center frequency are boosted or attenuated; others remain unchanged.	The center of the frequency range where the boost (or an attenuation) is applied.	Controls the bandwidth. Higher values result in a narrower band.	The boost (in dB) to be applied. Negative values attenuate the frequencies.
notch	Notch (band-stop) filter. Opposite of a bandpass filter: frequencies around the center are attenuated; others remain unchanged.	The center of the frequency range where the notch is applied.	Controls the bandwidth. Higher values result in a narrower band.	Not used
allpass	Second-order allpass filter. All frequencies pass through, but changes the phase relationship between the various frequencies.	The frequency where the center of the phase transition occurs (maximum group delay).	Controls how sharp the phase transition is at the center frequency. Higher values result in a sharper transition and a larger group delay.	Not used

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Methods

It inherits all methods from AudioNode.

getFrequencyResponse

Parameters	Type	Description
frequencyArray	Float32Array	Array of frequencies (in Hz), which you want to filter.
magResponseOutput	Float32Array	Output array to store the computed linear magnitude values for each frequency. For frequencies outside the range [0, $\frac{sampleRate}{2}$], the corresponding results are NaN.
phaseResponseOutput	Float32Array	Output array to store the computed phase response values (in radians) for each frequency. For frequencies outside the range [0, $\frac{sampleRate}{2}$], the corresponding results are NaN.
length	number	The number of frequency values to process. It should match the length of all input and output arrays.

Returns undefined.

Remarks

frequency

• Float. Default: 350.
• Range: [10, $\frac{sampleRate}{2}$].

detune

• Float. Default: 0.

Q

• Float. Default: 1.
• Range:
  • For lowpass and highpass is [-Q, Q], where Q is the largest value for which $10^{Q/20}$ does not overflow the single-precision floating-point representation. Numerically: Q ≈ 770.63678.
  • For bandpass, notch, allpass, and peaking: Q is related to the filter’s bandwidth and should be positive.
  • Not used for lowshelf and highshelf.

gain

• Float. Default: 0.
• Range: [-40, 40].
• Positive values correspond to amplification; negative to attenuation.

type

• BiquadFilterType. Default: "lowpass".