(I think my first post here!)
I recently bought a Google Nexus 7 and was having annoyance of email receive notification sound through the night. Of course I would have preferred to receive visual notifications but not the audio ones. So here is how I fixed it: In case of Android Jelly Bean running on Google Nexus 7, here is how I disabled the Email Notification sounds: Settings->Sound->Volumes->Notification volume control down to zero. And in the 'email' app setup to receive notification based on accounts and preferences.