Windows 10: how to turn off random Bling sound

every now and then, my wife's laptop makes a short sharp "Bling!" sound. It is becoming annoying. It is not related to the arrival of any incoming email, nor to any outstanding update. We had two quite days over the weekend, now it started again. Once every 10-20 or 30 minutes. We can't find any logic, any cause-effect relationship. There is no visual clue.
I went to Settings->Notifications and turned off everything I could. I also went to Outlook options and turned off the "Make a sound" on arrival of new mail.
We don't want to turn off sound completely, because Skype is running. In the Open Volume Mixer, I turned down the System Sounds while leaving Skype and Chrome on high.
I wonder what the culprit could be and how to turn it off. There is not much else running on the laptop, except for a standard Office installation from my workplace. New Dell, purchased Feb 2016.

:)

 

DRIVER_IRQL_NOT_LESS_OR_EQUAL

I completely reset my PC but problem not solved .Now recently I got sysyem_service_exception and it tell to restart but it switched off and when I start power light blings Cd writer starts but hard disk light bling for some seconds and switched off and
laptop does not turn on .Is there any hardware problem ??

 

Nokia N82

There is AGPS, I read it somewhere confirmed, and I saw a menu where you can turn rotation off.

 

You can right click the Volume (speaker) icon in the taskbar by the clock and choose Sounds. Then highlight each sound scheme with a speaker in front of it and press the Test button to play the sound. Once you recognize what the particular sound is, you can find out what is causing it.