AudioKit output changes to ear speakers

Question

I implemented the AudioKit "MICROPHONE ANALYSIS" example https://audiokit.io/examples/MicrophoneAnalysis/ in my App.

I want to analyze the microphone input frequency and then play the correct note which is near the frequency which was determined.

Normally the sound output is the speaker or a Bluetooth device connected to my iPhone but after implementing the "MICROPHONE ANALYSIS" example the sound output changed to the tiny little speaker on the top of the iPhone which is normally used when you get a call. How can I switch to the "normal" speaker or to the connected Bluetooth device like before?

var mic: AKMicrophone!
var tracker: AKFrequencyTracker!
var silence: AKBooster!


func initFrequencyTracker() {
        AKSettings.audioInputEnabled = true
        mic = AKMicrophone()
        tracker = AKFrequencyTracker(mic)
        silence = AKBooster(tracker, gain: 0)
    }

    func deinitFrequencyTracker() {
        plotTimer.invalidate()
        do {
            try AudioKit.stop()
            AudioKit.output = nil
        } catch {
            print(error)
        }
    }

    func initPlotTimer() {
        AudioKit.output = silence
        do {
            try AudioKit.start()
        } catch {
            AKLog("AudioKit did not start!")
        }
        setupPlot()
        plotTimer = Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(updatePlotUI), userInfo: nil, repeats: true)
    }

    func setupPlot() {
        let plot = AKNodeOutputPlot(mic, frame: audioInputPlot.bounds)
        plot.translatesAutoresizingMaskIntoConstraints = false
        plot.alpha = 0.3
        plot.plotType = .rolling
        plot.shouldFill = true
        plot.shouldCenterYAxis = false
        plot.shouldMirror = true
        plot.color = UIColor(named: uiFarbe)
        audioInputPlot.addSubview(plot)

        // Pin the AKNodeOutputPlot to the audioInputPlot
        var constraints = [plot.leadingAnchor.constraint(equalTo: audioInputPlot.leadingAnchor)]
        constraints.append(plot.trailingAnchor.constraint(equalTo: audioInputPlot.trailingAnchor))
        constraints.append(plot.topAnchor.constraint(equalTo: audioInputPlot.topAnchor))
        constraints.append(plot.bottomAnchor.constraint(equalTo: audioInputPlot.bottomAnchor))
        constraints.forEach { $0.isActive = true }
    }

    @objc func updatePlotUI() {
        if tracker.amplitude > 0.1 {
            let trackerFrequency = Float(tracker.frequency)

            guard trackerFrequency < 7_000 else {
                // This is a bit of hack because of modern Macbooks giving super high frequencies
                return
            }

            var frequency = trackerFrequency
            while frequency > Float(noteFrequencies[noteFrequencies.count - 1]) {
                frequency /= 2.0
            }
            while frequency < Float(noteFrequencies[0]) {
                frequency *= 2.0
            }

            var minDistance: Float = 10_000.0
            var index = 0

            for i in 0..<noteFrequencies.count {
                let distance = fabsf(Float(noteFrequencies[i]) - frequency)
                if distance < minDistance {
                    index = i
                    minDistance = distance
                }
            }
            //                let octave = Int(log2f(trackerFrequency / frequency))

            frequencyLabel.text = String(format: "%0.1f", tracker.frequency)

            if frequencyTranspose(note: notesToTanspose[index]) != droneLabel.text {
                note = frequencyTranspose(note: notesToTanspose[index])
                droneLabel.text = note
                DispatchQueue.main.asyncAfter(deadline: .now() + 0.03, execute: {
                    self.prepareSinglePlayerFirstForStart(note: self.note)
                    self.startSinglePlayer()
                })
            }
        }
    }

    func frequencyTranspose(note: String) -> String {
        var indexNote = notesToTanspose.firstIndex(of: note)!
        let chosenInstrument = UserDefaults.standard.object(forKey: "whichInstrument") as! String
        if chosenInstrument == "Bb" {
            if indexNote + 2 >= notesToTanspose.count {
                indexNote -= 12
            }
            return notesToTanspose[indexNote + 2]
        } else if chosenInstrument == "Eb" {
            if indexNote - 3 < 0 {
                indexNote += 12
            }
            return notesToTanspose[indexNote - 3]
        } else {
            return note
        }
    }

Answer 1

It's a good practice to control the session settings, so start by creating a method in your application to take care of that during initialisation.

Following up, there's an example where I set a category and the desired options:

func start() {
    do {
        let session = AVAudioSession.sharedInstance()
        try session.setCategory(.playAndRecord, options: .defaultToSpeaker)
        try session.setActive(true, options: .notifyOthersOnDeactivation)
        try session.overrideOutputAudioPort(AVAudioSession.PortOverride.speaker)
        try AudioKit.start()
    } catch {
      // your error handler
    }
}

You can call the method start where you make the call to AudioKit.Start() in initPlotTimer.

The example above is using the AVAudioSession, which I believe is what AKSettings wraps (please feel free to edit my answer to not mislead future readers, as I'm not looking at the AudioKit source-code at the moment).

Now that AVAudioSession is exposed, let's stick with the method offered by AudioKit since that's what you're dealing with.

Here's another example using AKSettings:

func start() {
        do {
            AKSettings.channelCount = 2
            AKSettings.ioBufferDuration = 0.002
            AKSettings.audioInputEnabled = true
            AKSettings.bufferLength = .medium
            AKSettings.defaultToSpeaker = true
            // check docs for other options and settings

            try AKSettings.setSession(category: .playAndRecord, with: [.defaultToSpeaker, .allowBluetooth])
            try AudioKit.start()
        } catch {
            // your handler
        }
}

Have in mind that you don't necessarily have to call it start, or run AudioKit's start method, I'm just exposing the initialisation phase, to make it readable to you and other use-cases.

Reference:

https://developer.apple.com/documentation/avfoundation/avaudiosession/categoryoptions

https://audiokit.io/docs/Classes/AKSettings.html