I have a Samsung Galaxy S3 and the phone was in my pocket. I forgot that my credit card was also in the same pocket and just out of nowhere my phone played the notification sound, so I pulled it out of my pocket and there were no notifications; no new email or SMS, nothing.
So then I pulled the card out and swiped it near the back of my phone, and then the sound played again. I did it like 20 times and it always happens. Why does my phone play the notification sound when I wave the credit card at the back of it?