Ugly Noise from Laptop Headphone Jack with AC Power

I plugged a 3.5mm stereo cable from my laptop to some speakers, and there was a horrible noise over the music I was trying to play. I thought at first that the audio cable was bad, but I noticed the problem went away if the AC adapter was unplugged from the computer. Interference from the surge protector's other plugs & transformers resulted in interference. Plugging the AC adapter into an power outlet on another wall solved the issue.