Have you just made a call to someone and they can't hear you? Or are you struggling to hear them? You want to play your music out load but hear no sound? Or maybe you're not being made aware of notifications you are receiving by hearing that little ping? Whatever the issue, you will want to fix your iPhone speaker as soon as possible.
This is a common problem that has been reported by Apple users, so take comfort in the fact that you are not the only one.