I am a neophyte nexus user, a bit computer literate. Updated to 4.3 on nexus the other day. I've been installing certain apps trying to get set up for a trip. Acquired a very annoying notification sound every 20 - 30 seconds. I've looked everywhere. Can't get rid of the notification sound and I don't think it's attached to email as I don't get that much and certainly not that frequently.