voice what voice
Yeah, it gives a voice notification. I'm not sure of exact words but something like "Your virus database has been updated". If you haven't heard it, the reason may be your settings. I believe the default setting is that nothing will be displayed if a full screen application is running. Now that I think of it, that seems consistent with my experience. In other words, I can have application windows and still get the alerts as long as I don't have any application window maximized, i.e. using full screen.
If you open the Avast control panel to the Summary screen, with Current Status selected on the left side of the screen, and then click "Change settings", you'll see options regarding alerts from Avast.