If you are loading a specific page then you might be able to inject JavaScript to disable the sounds. Another option is to mute the correct channel with Phone.SetMute. Make sure to use Try / Catch with SetMute as it will throw an exception if the Do Not Distribute option is enabled (unless you handle the special permission).
Great, how can I inject Javascript code on the webpage im showing? In addition, my webpage autosaves progress once webpage is closed. I need to somehow get the WebView know that the user minimized the App or closed it. How can I make it? Thanks