Hi, My headphone is QC20 noice-cancelling one. few days i experienced that if i tun on Noice-canclation it makes "HUMMMMMMMMMMMMM" sound near my laptop. i tried to unplug all connection from my laptop. then i tried to disconnect from laptop and hearing sound less. while i keep little bit away from Laptop, sound gone. mean no Hummm sound anymore. i figure-out if i make my headphone body part near of any electric device then it keeps sound on ear 'HUMMM" does anyone have this experience and how to solve it ?