Help Annoying sound bug

[bsk]

I am getting this frequent annoying sound whenever I turn my lock screen off and start using my Galaxy Nexus.

Almost immediately after the unlock-sound has chimed this other sound plays. After a while the sound returns, often playing several times over in one 'sequence'. Then again, and again, and again. Always seemingly unrelated to any specific apps or action on my part. It is incredibly annoying to say the least.

I've tried several different settings - but no luck. And it doesn't matter if I have Wifi, 3G or Sync tuned on or off.

The only thing that helps is if I turn off the sound completely or lock the screen back up - which isn't exactly a solution to the problem.

I've had the problem once in the past and was able to solve it via some google'ing, but I can't seem to find fix now.
I have no idea, why the problem suddenly returned...

I really hope some of you can help, because this driving me crazy.

 

[Digital Controller]

Try removing the battery reinserting and restarting the device first...

Otherwise is your device rooted/romed?

 

[Tim K]

NFC

Do you keep any credit cards in the same pocket or in the case of your phone?

If your phone comes in contact with a chipped credit card it will play a weird chime. Apparently new passports as well.

You can either keep NFC chips away from your phone or turn NFC off if you don't use it.

 

[bsk]

The phone was communicating with my student ID-card. Problem solved! Thanks a million