Baby hearing

My baby is 8 weeks old he passed his hearing test in the hospital the day after he was born but sometimes I get concerned he doesn't hear well or wonder if he just zones noises out? Sometimes he will react by looking at me when I sing to him and he will startle when dosing off on my shoulder and I start to talk but often loud noises and toys don't seem to startle him and he has no reaction. Anyone else experience this? Am I just being paranoid?