Baby doesn't startle at sounds..

Baby is almost 4 weeks old and doesn't really turn toward noises or startle at loud noises. I've banged pot and pans together and she barley noticed, she didnt even noticed when the people took the door off the get the new fridge inside and it was pretty loud. Am I just being paranoid or could she have some hearing problems? She coos and things and passed her hearing test at the hospital.