QUOTE(SubRosa @ Feb 11 2016, 03:32 PM)
Did you install any new software lately? It could be that ALT + W is a keyboard shortcut for something else you have that is running, and it is doing whatever it does in the background. Or failing to do it, and making that sound.
I think if that was the problem, then Skyrim/Fallout would have the same issues. This has to be something in Oblivion itself.
Does it happen with both Alt keys? It might just be that you mapped the wrong one, and it's failing to recognise the combo.