Are you talking about ear tubes you had put in? I had those when I was a kid and everything did sound louder for a while - I don't remember how long but my mom said it lasted around a month, with the worst only being a week or 2. It's actually pretty common for sounds to be louder for awhile and most kids adjust to it pretty quickly. Its worse if the child didn't have great hearing to begin with (I didnt, due to constant ear infections, so when I had tubes, the sounds I was hearing were actually normal, but so much louder for my ears, which is why it hurt). My mom had me wear ear plugs when I was going out around possible loud sounds, but even that didn't last long. So I'd say it's normal, what your girl is going through, but if it doesn't go away or causes her serious discomfort, you might want to get the tubes replaced.
Here's a website with some good info and you can find the same type of info on may sites:
http://www.cincinnatichildrens.org/health/info/ent/procedure/pe-tube.htm
Poor little girl , I have no idea about this someone else will I expect, but it seems you should take her back and let them check out the tubes as she is obviously in discomfort from what you describe, let us know how she is doing.