Thank you for bringing this issue to our attention.
The reason RadNotification plays no sound on mobile devices is that it uses ".wav" audio format, which unfortunately is not supported by most of the mobile devices browsers.
This limitation can be verified on the following test page
I have logged the issue as a feature request in our Public Feedback Portal. You can track its status, comment and vote for it here
Please, excuse us for the inconveniences caused by this issue.
As a small token of gratitude for reporting it, I have updated your Telerik points accordingly.
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