Caleb,
Sound transmission can definitely be a problem in the situation you described. Basically, it depends on whether hearing people above you bothers you. There are a number of solutions, both in the layout of the floorplan, as well as in construction details. Some 2x's and an airspace help a lot, or you could put soundboard in the cavities. This is also a convenient place to run pipes and wires, etc.
Good luck with your project
Gabel Holder