How to reduce noise while recording with AudioKit

问题

I am using AudioKit to record audio and display visualizer while recording and playing audio. It works good, But recorded audio has lots of background noise.

Is there any way to reduce noise? Here is the code for prepare recording

func prepareForRecording() {
    AKSettings.defaultToSpeaker = true
    // Patching
    outputPlot.node = mic
    micMixer = AKMixer(mic)
    micBooster = AKBooster(micMixer)

    // Microphone monitoring is muted
    micBooster.gain = 0 // Silent
    recorder = try? AKNodeRecorder(node: micMixer)
    if let file = recorder?.audioFile {
        player = try? AKAudioPlayer(file:file)
    }
    player?.completionHandler = playingEnded

    moogLadder = AKMoogLadder(player)

    mainMixer = AKMixer(moogLadder, micBooster)

    AudioKit.output = mainMixer

    if isMicPresent {
        AudioKit.stop()
        AudioKit.start()
    }
    currentSeconds = 0
    timer?.invalidate()
    timer = nil
}

来源：https://stackoverflow.com/questions/49507343/how-to-reduce-noise-while-recording-with-audiokit