Re: Mystery, Reoccuring Notification Sound
I hate to spoil everyones party, but there's so much crapware out there that it's pretty much impossible to tell you why your phone is doing this. The short & sweet answer is that it's NOT the default behavior of a normally operating phone to provide random audio notifications without an associated app generating them. Since the likelihood of your phone being the problem is rather low, it's probably some app/combination of apps that's causing the problem.
Solution: perform a Factory Reset (after backing up your contacts, calendar, SMS, Call Logs, etc.) and SKIP the initial Google account setup (this is crucial - this will keep the Google Play Store from automatically downloading all of your previous apps). Once the phone is configured, go back in and add your Google account.
DO NOT REINSTALL EVERY APP UNDER THE SUN!
Just update the preinstalled apps and use the phone for a few days. If the random notification problem is gone you've solved your basic problem - there's nothing wrong with the phone. Now install a handful of apps and wait a few more days before installing anything else.
If/when the problem starts happening again you know that you've installed some app that's causing the problem or that doesn't interact well with some other app (usually an app with a similar purpose, for example - two different messaging apps; or two social networking apps). So go back and uninstall the last batch of apps that you put on the phone (you are keeping track, right?).
Sent from my rooted, debloated, deodexed Sinclair ZX-80 running CM -0.001 using Tapatalk 4