iOS AudioKit Hight Pass Filter

Question

I am trying to detect pitch from iOS microphone with AudioKit, and here is the code

    init() {
        guard let input = engine.input else {
            fatalError()
        }

        mic = input

        filter = HighPassFilter(mic, cutoffFrequency: 200, resonance: 40)
        silence = Fader(filter, gain: 0)
        tracker = PitchTap(silence) { pitch , amp in
            DispatchQueue.main.async {
                print(pitch[0], amp[0])
                self.update(pitch[0], amp[0])
            }
        }
        engine.output = filter
    }

    func start() {
        recordFrequency = []
        do {
            try engine.start()
            tracker.start()
        } catch let err {
            Log(err)
        }
    }

Because there's always some detect (frequency 20 to 200) when I don't make sounds, I add a high pass filter to filt the sound lower than 40 dB and 200 frequencies, But it seems not work, what should I do?

Thanks.

Answer 1

It looks like you just have some connection point issues. Try putting the tracker before you make the signal silent:

    filter = HighPassFilter(mic, cutoffFrequency: 200, resonance: 40)
    tracker = PitchTap(filter) { pitch , amp in
        DispatchQueue.main.async {
            print(pitch[0], amp[0])
            self.update(pitch[0], amp[0])
        }
    }
    silence = Fader(tracker, gain: 0)
    engine.output = filter