Possessed Smartphone

I think my phone may be possessed.  I was sitting on my deck earlier, and out of the blue my phone started playing the sound from some random ad while in my pocket. I pulled it out to see what the hell was going on, and found that no apps were even open. The audio was coming from NOWHERE.  It eventually stopped, and I rebooted the phone out of pure confusion.  Hasn’t done it since.  But still, a little bit odd.