         
         AudioKit.stop()
         
-        let questionFolderURL = URL(fileURLWithPath: folderList.object(at: currentQuestion-1) as! String, relativeTo: audioFolderURL)
+        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)

        audioFolderURL = URL(fileURLWithPath: "audio", relativeTo: Bundle.main.bundleURL)
        
        do {
            folderList = try FileManager.default.contentsOfDirectory(atPath: audioFolderURL.path) as NSArray
            print(folderList);
        } catch let error {
            print("Error loading audio files: \(error.localizedDescription)")
        }

        return true
    }
    
    func sortFunc(num1: String, num2: String) -> Bool {
        return num1 < num2
    }
    
    func randomiseCorrectAnswers() {
        correctAnswers.removeAll()
        for i in 1...totalQuestions {
