如何在iPhone上进行实时声音/信号处理？

import AVFoundation

let audioSession = AVAudioSession.sharedInstance()
let audioEngine = AVAudioEngine()

try audioSession.setCategory(.playAndRecord, mode: .default, options: [.defaultToSpeaker, .mixWithOthers])
try audioSession.setActive(true, options: [])

let inputNode = audioEngine.inputNode
let effectNode = AVAudioUnitEQ(numberOfBands: 1)
effectNode.bypass = false
effectNode.bandGain = 10
effectNode.bandFrequency = 1000

audioEngine.attach(effectNode)
audioEngine.connect(inputNode, to: effectNode, format: nil)
audioEngine.connect(effectNode, to: audioEngine.outputNode, format: nil)

audioEngine.start()

audioEngine.stop()