The `BiquadFilterNode`

interface represents a simple low-order filter, and is created using the `AudioContext.createBiquadFilter()`

method. It is an `AudioNode`

that can represent different kinds of filters, tone control devices, and graphic equalizers.

Documentation BiquadFilterNode by Mozilla Contributors, licensed under CC-BY-SA 2.5.

See:

### Variables

`read onlyfrequency:AudioParam`

Is an a-rate `AudioParam`

, a double representing a frequency in the current filtering algorithm measured in hertz (Hz).

`read onlygain:AudioParam`

Is an a-rate `AudioParam`

, a double representing the gain used in the current filtering algorithm.

Is a string value defining the kind of filtering algorithm the node is implementing.

`type`

Description
`frequency`

`Q`

`gain`

`lowpass`

`highpass`

`bandpass`

`lowshelf`

`highshelf`

`peaking`

`notch`

`allpass`

Standard second-order resonant lowpass filter with 12dB/octave rolloff. Frequencies below the cutoff pass through; frequencies above it are attenuated. | The cutoff frequency. | Indicates how peaked the frequency is around the cutoff. The greater the value is, the greater is the peak. | Not used |

Standard second-order resonant highpass filter with 12dB/octave rolloff. Frequencies below the cutoff are attenuated; frequencies above it pass through. | The cutoff frequency. | Indicates how peaked the frequency is around the cutoff. The greater the value, the greater the peak. | Not used |

Standard second-order bandpass filter. Frequencies outside the given range of frequencies are attenuated; the frequencies inside it pass through. | The center of the range of frequencies. | Controls the width of the frequency band. The greater the `Q` value, the smaller the frequency band. |
Not used |

Standard second-order lowshelf filer. Frequencies lower than the frequency get a boost, or an attenuation; frequencies over it are unchanged. | The upper limit of the frequencies getting a boost or an attenuation. | Not used | The boost, in dB, to be applied; if negative, it will be an attenuation. |

Standard second-order highshelf filer. Frequencies higher than the frequency get a boost or an attenuation; frequencies lower than it are unchanged. | The lower limit of the frequencies getting a boost or an attenuation. | Not used | The boost, in dB, to be applied; if negative, it will be an attenuation. |

Frequencies inside the range get a boost or an attenuation; frequencies outside it are unchanged. | The middle of the frequency range getting a boost or an attenuation. | Controls the width of the frequency band. The greater the `Q` value, the smaller the frequency band. |
The boost, in dB, to be applied; if negative, it will be an attenuation. |

Standard notch filter, also called a band-stop or band-rejection filter. It is the opposite of a bandpass filter: frequencies outside the give range of frequencies pass through; frequencies inside it are attenuated. | The center of the range of frequencies. | Controls the width of the frequency band. The greater the `Q` value, the smaller the frequency band. |
Not used |

Standard second-order allpass filter. It lets all frequencies through, but changes the phase-relationship between the various frequencies. | The frequency with the maximal group delay, that is, the frequency where the center of the phase transition occurs. | Controls how sharp the transition is at the medium frequency. The larger this parameter is, the sharper and larger the transition will be. | Not used |

### Methods

`getFrequencyResponse (frequencyHz:Float32Array, magResponse:Float32Array, phaseResponse:Float32Array):Void`

From the current filter parameter settings this method calculates the frequency response for frequencies specified in the provided array of frequencies.