https://stackoverflow.com/questions/11271991/uri-to-default-sound-notification 

       Context context = getApplicationContext();
    long[] vibrate = new long[] { 1000, 1000, 1000, 1000, 1000 };
    Intent notificationIntent = new Intent(context, MainActivity.class);

    PendingIntent contentIntent = PendingIntent.getActivity(context,
            0, notificationIntent,
            PendingIntent.FLAG_CANCEL_CURRENT);

    Resources res = context.getResources();
    Notification.Builder builder = new Notification.Builder(context);

    builder.setContentIntent(contentIntent)
            .setSmallIcon(R.drawable.notif)
            .setTicker("lastWarning")
            .setWhen(System.currentTimeMillis())
            .setAutoCancel(true)
            .setVibrate(vibrate)
            //.setContentTitle(res.getString(R.string.notifytitle)) 
            .setContentTitle("Notification")
            .setSound(Settings.System.DEFAULT_NOTIFICATION_URI)
            //.setContentText(res.getString(R.string.notifytext))
            .setContentText("Notification text"); 

    // Notification notification = builder.getNotification(); // until API 16
    Notification notification = builder.build();

    NotificationManager notificationManager = (NotificationManager) context
            .getSystemService(Context.NOTIFICATION_SERVICE);
    notificationManager.notify(NOTIFY_ID, notification);