Can't tell you if it's "normal" but my little guy was like that. He would hear and react to my husband closign his CELL PHONE! That was in the hospital. He startled and looked around for the noise at 24 hours old.
Sudden noises and things like that freaked him out in the beginning, BIG time. I know of so many kids that just konk out in white noise- with him it was the worst.
I have one VERY loud SIL and everytime she started talking loudly he started crying, he hated loud people. Now at 18 months he is literally the life of the party. But to this day he does not just pass out like other tired toddler, he needs a very aware and active transitioning to "sleep time". A seperate room, darker at night, quieter- he will sleep better with a fan on, but do NOT have it on when he needs to fall asleep-he will investigate the sounds, it hinder's is falling asleep.
My little guy outgrew the total freakout in regards to sounds, but to this day he is very aware of his acoustic surroundings.
I would definitely check for food intolerances (dairy in your intake for example), as that be a sign for an intolerance.
My little guy was very easy to startle at that age- and I guess some babies are just like that. I was told non-stop how I should MAKE extra noise to "get him used to sounds"
, great advice. I did not MAKE him that aware of acoustics, he just is that way. He is better about it now, but he was never a baby that slept through crowds and noises, he is just WAY to curious, always was, even as a newborn.