So now you have to understand first understand what installTap does when you call it on inputNode? Ans: it just listens to Node's Buffer but before installation we have to tell it which Bus to installTap, what will be the bufferSize that will come from inputNode, and what will be the audioFormat of input of inputNode so whenever you want change the input microphone there are proper safe flow which has to be followed. class AudioProcessor { // Audio resources var audioEngine: AVAudioEngine! var inputNode: AVAudioInputNode! var formatIn: AVAudioFormat static let sharedInstance = AudioProcessor() private init() { self.audioEngine = AudioResources.sharedInstance.audioEngine self.inputNode = self.audioEngine.inputNode self.formatIn = self.inputNode.inputFormat(forBus: 0) } open func pause() { self.audioEngine.inputNode.removeTap(onBus: 0) self.audioEngine.stop() } open func resume() { if !self.audioEngine.isRunning { self.installTap() self.audioEngine.prepare() self.audioEngine.inputNode.volume = 1.0 try self.audioEngine.start() } } func installTap() { self.audioEngine = AudioResources.sharedInstance.audioEngine self.inputNode = self.audioEngine.inputNode self.formatIn = self.inputNode.inputFormat(forBus: 0) self.inputNode.installTap( onBus: 0, bufferSize: 4096, format: self.formatIn ) { (buffer,_) in //DO WHATEVER YOU WANT TO DO WITH BUFFER } } } //After that add notification observers in your VC NotificationCenter.default.addObserver(self, selector: #selector(self.handleRouteChange(_:)), name: AVAudioSession.routeChangeNotification, object: nil) @objc func handleRouteChange(_ notification: Notification) { let devices = AVAudioSession.sharedInstance().availableInputs ?? [] let currentDevice = AVAudioSession.sharedInstance().currentRoute.inputs.first?.portName ?? "" if let inputDevicePortDescription = devices.first(where: {$0.portName == currentDevice}) { AudioProcessor.sharedInstance.pause() AudioProcessor.sharedInstance.resume() } }