No ring or alert tomes

I have an I-phone 3G and although the touch screen is cracked it functions fine. However I have no ring, keypad, alert or alarm tones. The speaker works fine when I make calls, and I can hear the other person clearly. The mute switch is operating OK as it is switching modes (indicated by mute / non-mute icon). I can play music through ear phones but not through speaker. Also the vibrator works fine. This fault developed before touch screen cracked so I don't think it is connected to this fault. Any ideas?