我写了这个，但我仍然无法过滤100 Hz以上的频率。
microphone = AKMicrophone()
tracker = AKFrequencyTracker(microphone, hopSize: 200.0, peakCount: 2000.0)
lowFilter = AKLowPassFilter.init(microphone, cutoffFrequency: 100.0, resonance: 0)
silence = AKBooster(tracker, gain: 0)
AudioKit.output = silence
try!AudioKit.start()
lowFilter.start()
microphone.play()
tracker.start()