My 4s started making this strange sound like a ping/water drop! What is it?
First time it happened my phone was locked sitting in my lap, nothing lite up just made the sound, 15-20min later I plugged it in to charge and it made the sound again. Nothing ever comes up in notifications just bluooop sound! It has also happened while I have been using my iPhone, while in iMessage and other apps! I have checked every app on my iPhone and sound setting I can think of and can't figure out were it is coming from or why!!