My iPhone4s sound has stopped working

My iPhone 4s sounds have stopped working! They were working this morning and then at a random point in the afternoon I tried to facetime my friend. I couldn't hear her and she couldn't hear me. My sound is turned up in the settings! People can't hear me and I can't hear them. I get no sounds from text tones, phone calls, alerts, Siri can't hear me (and I can't hear "her"), no alarm sounds... Nothing! Vibrate work though. I have not dropped my phone nor has it come in contact with water. This was all completely out of the blue. Please help!