Bugfix. Paths to sound files should be absolute.

converse.js

@@ -349,7 +349,7 @@
         this.playNotification = function () {
             var audio;
             if (converse.play_sounds && typeof Audio !== "undefined"){
-                audio = new Audio("sounds/msg_received.ogg");
+                audio = new Audio("/sounds/msg_received.ogg");
                 if (audio.canPlayType('/audio/ogg')) {
                     audio.play();
                 } else {