The baby can hear you long before they can hear sounds outside the womb. They begin to hear the sounds of the womb (your heartbeat, the swishing of amniotic fluid, your voice, etc.) around 16 weeks.
the doc told me 22 weeks, its when the inner ear is completely formed so he can hear everything u can at 22 weeks :)
Ya know that is a very good question and I used to know the answer... I think it is between 23-30 weeks! I will have to google it!