What does repeating beeps mean during charging? During a software update to 7.0.6 this iPhone 4S abruptly turned off and would not turn back on (screen blank).

When plugged into the charger or computer it beeps on a regular basis with the default system ding sound.

iTunes recognizes it, allows photos to be backed up, but requires that I unlock the phone to refresh it or back it up, which I can't do because the display is off. Find my iPhone shows it in its correct location - which just verifies the wifi chipset, I suppose.

Performing the reset and restart procedures on Apple's website doesn't do anything.

The display is black the entire time.

While I'm pursuing other things, I'd like to find out why the phone is beeping while charging or plugged into the computer.  Does the beeping indicate something relevant to the issue I'm facing?
No, its not notifications beeping. 
I have a dropped iPhone 4S here, that has a cracked screen. 
Plugging it into a charger results in a constant beeping every 6 seconds exactly with no display. I have no idea if it's because the display/touchscreen is damaged or if the phone has crashed and is displaying a blank screen as i have no idea of the extent of the damage. 
I'd say it's related to a serious hardware failure that the beeping occurs. 
It's not a notification issue as the phone doesn't have time to boot up iOS before the beeping starts. Beeps way too soon and notifications wouldn't roll in regular as 6 seconds exactly for over an hour.