QtWebEngine donot support mp3 audio
QtWebEngine donot support html5 audio which source type is mp3
See a similar question: http://lists.qt-project.org/pipermail/qtwebengine/2014-June/000061.html
The summary is that the mp3 support isn't built by default because you need a license for the codec to be able to use it in your application.
i should need to recomplie qt with qtWebEngine??