Faint buzzing sound from Magsafe port?

[lyoncab]

Not sure if anybody has a really faint buzzing sound on their new 13" MB Airs. It's a faint buzz that I can hear regardless if it's charging or not. Though I have to put my ear a bit close to the machine. The sound seems to be coming from the Magsafe port, not sure if the sound is just the power/electricity. Don't get me wrong, it's a very quiet machine, just wondering if this sound is normal, thanks!