Name
Equalizer -- RBJ peaking equalisation biquad IIR filter
Synopsis
equalizer frequency[k] width[q|o|h|k] gain
Function
Apply a two-pole peaking equalisation (EQ) filter. With this filter, the signal-level at and around a selected frequency can be increased or decreased, whilst (unlike bandpass and bandreject filters) that at all other frequencies is unchanged.

Frequency gives the filter's central frequency in Hz, width, the band-width, and gain the required gain or attenuation in dB. Beware of clipping when using a positive gain.

In order to produce complex equalisation curves, this effect can be given several times, each with a different central frequency.

See also bass and treble for shelving equalisation effects.

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