Hopefully, if all is well, we will be eleven weeks this week - so just behind the two of you ladies - from what I have read, the three bones in the inner ear will strart developing in the fifteenth week - but the auditory centers in the brain are quite ready yet - so he can't understand the random sounds that he might be hearing until about twenty weeks and then he can actually react to noises!
My preg. book says week 20, the external ears are formed, and they can hear loud noises from the outside world! I'm 12wks also!
Good luck to you!