let settings = [
        AVFormatIDKey: Int(kAudioFormatMPEG4AAC),
        AVSampleRateKey: 44100.0,
        AVNumberOfChannelsKey: 1,
        AVEncoderAudioQualityKey: AVAudioQuality.high.rawValue
        ] as [String : Any]

    do {

        audioRecorder = try AVAudioRecorder(url: audioFilename, settings: settings)
        audioRecorder.delegate = self
        audioRecorder.record()