         
         // MARK: play audio fast
         stopButton.hidden = false
-        audioPlayer.currentTime = 0
         audioPlayer.rate = 2
         audioPlayer.play()
     }

        audioEngine.reset()
        
        audioPlayer.stop()
    }
    
    @IBAction func playSlowAudio(sender: UIButton) {

        
        // MARK: play audio slow
        stopButton.hidden = false
        audioPlayer.rate = 0.5
        audioPlayer.play()
    }
