Acoustic Noise Reduction

So in another forum I explained how I was using power screwdriver motors to move my rocker bogie suspension system. So I was wondering if you guys had any ideas on how to dampen the acoustic noise(not the electrical noise) coming from these motors. They use planetary gearboxes which I know are notorious for being loud but I need the torque that they provide. I was planning on using some sound proofing material to dampen the sound but I was wondering if you had any ideas. I know it is kind of a weird topic but thanks for your help. 

As ChuckCrunch says, rubber

As ChuckCrunch says, rubber gaskets. I always mount my harddrives and fans with those, removes a lot of noise.