My little man is like this. He's 1 now but he's always been sensitive to sounds. I actually posted on here about it too because I wasn't sure if it was normal but no one responded. 🤷🏼♂️ The only thing I've learned to do with him is face the noise so he can see what it is. I believe this helps him even though he does still jump.
It depends on the noise and its really weird. Eg the dog barks she doesn’t flinch but if my partner sneezes or sniffs she cries 🙃 We just start laughing and being silly to make her smile instead of crying and it works 50% of the time
is he still little? it could just be startling especially if he isnt used to it