Here are some links that has the list on what babies should be able to do by so and so month.

http://www.babycenter.com/0_milestone-char...nths_1496585.bc

http://baby.topresource.net/baby-first-yea...nt-progress.php

If you are still worried, take him to see a doctor. I remember the paed checking for my baby's hearing after he was born, not directly after birth, but I think in one of the earlier check-ups. The paed checked with the Y shaped thing that vibrates after you hit it on something..