Earth Loop Hum

Hi,

Running VoIP from my laptop with the power supply connected to the mains introduces a 50Hz earth loop hum into the headset that is really annoying for the other party. Unplugging the laptop from the mains and running on batteries fixes this problem - but the batteries run down! Also, muting the microphone also fixes the problem for the other party

- but they can't hear me speak. Can anyone suggest a possible solution. I understand about removing the earth wire from the plug but the power supply is already connected via a

Thanks in advance. Robbieg