public class TestEditorWindow : UnityEditor.EditorWindow {

            [MenuItem ("Window/My Window")]
            static void Init () {
                // Get existing open window or if none, make a new one:
                var window = (TestEditorWindow)EditorWindow.GetWindow (typeof (TestEditorWindow));
                window.Show();
            }

            private int index = 0;

            public void OnGUI() {
                var padding = 5;
                var width = Screen.width - 2*padding;
                var lineHeight = EditorGUIUtility.singleLineHeight;

                var audioclipNames = FileNamesFromFolder<AudioClip>("Audiofiles");

                if(audioclipNames.Length <= 0) return;

                index = EditorGUI.Popup(new Rect(padding, padding, width, lineHeight), "test: ", index, audioclipNames);

            }


            public string[] FileNamesFromFolder<T>(string folderpath) where T : UnityEngine.Object {
                var allfiles = Resources.LoadAll<T>(folderpath);
                return allfiles.Select(obj => obj.name).ToArray();
            }

        }