I'm really puzzled Boy, this is tough to explain. There is this harp like, "Blouing (pause) doom-doom" sound that plays randomly on my iMac 2011 running Lion. It plays for about 1.5 second then no occurrence for minutes or hours. Apps that are running or started: Adium, Splashtop streamer, Dropbox, Evernote (growl not enabled), sometimes Chrome sometimes not. It's not also from a external interruption like a contact that pings me in Adium, say. For example, I heard it this morning at 6:18 while in bed; it was very quiet in the house. I don't use Mail, not an iCal notification either. Anyone ?