Custome notification sound is playing only if i have breakpoint windows universal 8.1

Hi when push notification is received i am displaying toast notification. i have issue that is if i have break point in below function then and then only custom notification sound is playing else notification sound is not playing.I thought might be audio is not loading so i added Task.delay for 2 sec/5 sec but no luck. What could be the issue.

        public static void AddTostNotification(String xmlDocument)
    {

       List<string> messageSection = PushNotificationHelper.GetMessageAndLandingPage(xmlDocument);

       ToastTemplateType toastTemplate = ToastTemplateType.ToastText01;

        XmlDocument toastXml = ToastNotificationManager.GetTemplateContent(toastTemplate);
        XmlNodeList toastTextElements = toastXml.GetElementsByTagName("text");
        toastTextElements[0].AppendChild(toastXml.CreateTextNode(messageSection[0]));
      //  toastTextElements[1].AppendChild(toastXml.CreateTextNode(message));

        IXmlNode toastNode = toastXml.SelectSingleNode("/toast");
        ((XmlElement)toastNode).SetAttribute("launch", messageSection[1]);

        XmlElement audio = toastXml.CreateElement("audio");
        audio.SetAttribute("src", "ms-appx:///Assets/Guitar.wav");

        toastNode.AppendChild(audio);

        //launch tost immediatly
        ToastNotification toast = new ToastNotification(toastXml);
        ToastNotificationManager.CreateToastNotifier().Show(toast);

    }

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Dattatray