AVAudioEngine has a equalizer function. That has some of filter types. Here is a just sample code of the parametric equalizer. Project files is on the Github.

Center Frequency = 31Hz, 62Hz, 125Hz, 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 8KHz, 16KHz

Bandwidth(Q) = 0.5 octave

Of course, you can change number of band, center frequency, bandwidth.