We just put hardwood in the second level of our home - previously carpet. I have not noticed any problems - but my kids are high school and older and not running around upstairs. Actually, my flooring installer noticed that my subfloor had not been correctly nailed down. Many nails had popped and the floors were very squeaky under the carpet. He screwed the subfloor down and it is actually quieter with the hardwood now that the squeaks are gone! He also put a black paper material between the subfloor and the hardwood. He told me what it was for, but I forgot what he said, but he said it also helped a little with noise.

I removed the carpet from the stairs and refinished them - I love it, but the stairs are definitely a little noisier.

I love our new hardwood. It is a very ordinary, traditional 2 1/4 wide, 34inch oak.

unless you are sleeping under a bedroom with wood floors, they should be fine. we have big carpets over hardwood in a 3rd floor bedroom that is over our master bedroom on the second floor, as our son and daughter in law seem to keep late hours when they are visiting at christmas.

in our previous home, our daughter tap danced in her room. used to be quite the clatter in our dining room below!

I grew up in a home with hardwood everywhere my mom just put rugs in the bedrooms to help with the noise was never an issue when we were all at home.