Most of you probably do this all the time, but it might be a helpful tip to any newcomer.
One way to reduce noise in robots is to always twist power cables. It also looks better and you can group wires for other purposes with this method.
You simply mount the wires you need to twist on your cordless drill and fasten the other end in a vise or something similar. Tighten the wires and slowly turn the motor to twist the wires.
PS. You need to add some length to the wires as the length will be shorter afterwards.