Audio noise when screen touched

[Hovey]

I noticed today, while I had my phone plugged into my computer audio input, that there is a general noise, slightly crackly noise, coming out of the speakers. Nothing was playing. So I went to touch the screen, move the volume back and forth and you could here it intensify as I navigated the screen. Any one else experience this? I could not hear it in my headphones. I'm going to try another stereo input at home after work.