Sound keeps going out on Iphone 4s.

The sound keeps going out on my 4s. I turned on the ringer and reset my iphone, but i canthear any sound. I cant hear the clicks on the keyboard, music, or any audio. It also goes out while im listening to music, or if i tap it. I restart my phone, and sometimes it works and sometimes it doesnt. If you have any suggestions, please let me know.