No such thing as stupid questions
I think it depends on the type of basement. Some houses in CO have two levels, which some may consider a basement and an upstairs. But the basement is actually partially under the ground level. I had a home that had four levels, the main floor was ground level, then you went downstairs and it wsa partially below ground level, you went downstairs again and it was completely belowe ground. In that house (all of them are built different) you couldn't hear anyone from the top level, but you could the closer you got. So basically it was no different in sound overall (yes there was some difference but not a lot). This was mainly because the staircases were all open and there were doors that I would use to shut off the sound but it wasn't completely sound proof.
I just wanted to add that some basements in older houses are accessed from the outside. Also, some people may have a cellar that's not under the house at all.