Here is the hard reboot technique given me by my Mitsubishi tech contact.
Whether it will fix your sound problem is questionable. They are usually TV station connected.
Go to Set Up, Installation and Local Area. Uncheck local channels.
Change Local 1 to None.
Clear zip code. Guide will update.
Exit menus using Done links.
Turn off receiver and TV
Unplug receiver and detach satellite input.
After 2 minutes, replug and re-attach.
Set Local 1 to antenna.
Scan local channels.
Enter zip code. Guide will download.
For a soft reboot, remotely press Satellite, Action and Power, in turn.
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Bill Brenner