Question about ferrite maybe?

Just to add a little more info to this posting, for you loud stereo lovers(in your work vehicle) if you have any engine noise, hydraulic engine noise(from snow plows-salt shakers), or any other vehicle electrical noises getting into your amp or high powered stereo. Take the power wires and/or the input wires to the amp and wrap them around and thru those ferrite chokes we've all been collecting. It will take all electrical interference noise out of the picture. The more you wrap the wires the better the filtering. A friend of mine used to run a yellow warning light and the "whine" from it would trash the receive of his CB radio. I used a ferrite choke on the power wire for the light and all the noise was gone like magic. Hope this helps someone,,,