X60S audio (grounding?) problem: low humming when using the power supply

[Pooky]

Hi everybody

Every time the power supply (original) is connected to my x60s, the headphone output produces a noticable low humming sound which has not been present before. I'm using it quite often and it has become somewhat bothersome. Also, the volume of the hum increases everytime the sd card  is accessed. (source of the problem?)

I am quite sure the problem is related to the laptop itself: using other original power supplies or different power sockets at varying locations did not affect the issue. 

Also, everytime I touch the laptop at conducting spots (like the metal hinges of the display) the humming dissappears which could hint at a problem with the grounding of the device

I"ve searched the forum for solutions but so far i"ve not been successful.

Does anyone have experience with or a solution for this problem?

Thanks in advance

[Pooky]

Update:

Groundling the X60's hull manually seems to eliminate the Problem.

Given that the x60s power supply does not have a grounding wire, do you believe it is recommendable to add one oneself ( using the ground-connector on most AC outlet sockets) ?

[lead_org Microsoft MVP Contributor]

there are Lenovo thinkpad adapters with 3 prong connectors.