Q: iPhone 5 Speaker problem? ..or logic board problem?

Hello,

Anyone can help what can be this.
Yestersday, every time i had a call, i can't hear the "call ring" and no sound in the other side of the call. My girl call me and i can't hear again... but curiously the phone work well (i can play games, music, internet).
i dont understand what this problem...

Thanks for your attention..