     var playerB: AKAudioPlayer!
     var playerReference: AKAudioPlayer!
     var audioFolderURL: URL!
-    var folderList: NSArray!
+    var folderList: [String]!
     var totalQuestions = 0
     var currentQuestion = 1
     var correctAnswers = [Int]()

        return true
    }
    
    func randomiseCorrectAnswers() {
        correctAnswers.removeAll()
        for i in 1...totalQuestions {

        
        AudioKit.stop()
        
        let questionFolderURL = URL(fileURLWithPath: folderList[currentQuestion-1] as! String, relativeTo: audioFolderURL)
        let referenceAudioURL = URL(fileURLWithPath: "reference.wav", relativeTo: questionFolderURL)
        let whiteAudioURL = URL(fileURLWithPath: "white.wav", relativeTo: questionFolderURL)
        let filteredAudioURL = URL(fileURLWithPath: "filtered.wav", relativeTo: questionFolderURL)
