noise from laptop psu on audio out

[tiv48]

not an earth loop problem .the maplins unit is a smps . if the volume on the laptop is turned dowm the buzz goes. the buzz alters in frequence depending on what the laptop is doing. i have scoped the output of the psu and its clean off load. i have tried 2 inch ferrit rings on ac input and dc output .makes no difference. so i am still at a loss to explain this
rob t