My daughter also does this. She's always asking "what's that sound" (even something very quiet). We don't have an official diagnosis but I'm thinking it might be hyperacusis.
@Jamie what makes you think hyperacusis as compared to curiosity over new sounds? Shes indicating that sound seem painful too in some way?
@Christine She will cover her ears and say everyday sounds are "too loud". For example, when the furnace kicks on. She also is very sensitive to loud noises (like a microphone over a PA).
My daughter did it the other day in the car, but I had the windows down, and I think it was just too much for her. She has also done it when she doesn't like the music we are listening to. I never really thought much of it.
She could just be sensitive to the noise. Look into sensory processing sensitivity. I have it (it’s a not a disorder) it’s the just way my nervous systems operates.
Could be normal. Overstimulation is also a sign of ADHD though, not just autism.