weird static noise

[x200user]

Hi to all , I've recently started to notes some weird noise from my x200 laptop while it's plugged in for regular charging

the noise is quit repeatedly and with Constance.. kind of static sound

I've already disqualify my speaker mostly because the sound comes from the left side of my computer
and also tried few other original lenovo chargers..

is there anyone who know this kind of problem?...

thanks