cb speakers squeal

okay so before someone says "use the search feature" i already have and turned up nothing so here i am asking it. My cb radio is mounted to a cigarette plug thing from radio shack where you put the wire in and turn the nobs on it in case any one needs to know but when i just turn my key for the lights and radio to come on my speakers are fine. As soon as i turn my truck all the way on like crank it up my speakers have this high pitched squeal in them, my daddy said possibly could be inerference from the alternator but i was wondering what you guys think and any suggestions on fixing it. the speaker is a external speaker btw

 

Try wiring it direct to the battery. Is this a new radio or used?

 

the radio is used but i got it from the guy i worked for this summer on the farm it was in the work truck i drove it worked perfect then i have thought about wiring it direct but im worried about draining my battery