Take some of this compressed foam insullation, like they use underneath vynil siding amd contact glue it to the inside of the walls, from the floor up to about 36" high. This will damped the noise made by your feet hitting the walls. You can also put some underneath (bottom side) the flooring to dampen the noise. You can get this stuff at nay home builder or improvement store, like Lowes and Home Depot.

I used this same stuff on the floor of my aluminum john boat and it made a huge difference in the noise reduction.