Every now and then, on my Mac, I hear a bell. I have no idea what app it is, or why it's beeping at me.
My first thought was that it's coming from the Notification System in OS X 10.8 (I never heard such a thing on 10.7), but I turned off the sound notifications for every app listed in the Notification preferences.
Is there any way to tell what app is doing this to me?
UPDATE: I think it might have been Mail -- it has its own sound notification preferences, apparently. But I'm not certain, and the question as written still stands: how do you know where sound comes from?