Completely normal! Some babies are just a bit more sensitive my 9 month old has only just started to be calm when I sneeze/cough. Previously if I was BF and did either she'd get so scared and bawl her eyes out. She also used to get really scared hearing plastic/foil packets like a crisp packet opening would make her jump and cry! They're just getting used to new sounds so it's bound to be a bit daunting for them! They'll grow out of it
My child didn't and still doesn't like loud noises. From the moment she came home the house was usually always quiet. TV low if it was on. We didn't really have loud toys. She's normal, no neurological issues or anything of the sort but she still doesn't enjoy loud noises. Me either tbh. I jump at my own shadow to be fair and that doesn't make a noise 😅. I wouldn't worry. See how they are as they age.
My boy started doing this (more so when he had a cold) I was already in contact with the GP but they said some babies are just more sensitive to noise but she also said that because he's got a cold it could be that his ears are muffled or don't feel right and it's affecting them. Even though his cold has now gone he still puts his hands up to his ears if an ambulance or motorbike go past ... I made him cry the other day as we were chilling looking at picture cards and I think I said 'banana' a bit too loud 🫠🤣