Low frequency sound emitting out of Logitech z560

[SupermanCK]

Everytime when i turn off my computer, monitor, speakers...i keep on hearing a very low buzz...later i found out it was the Logitech z560 speakers making that annoying noise...anyone have this similar problem?
How can i fix this? The noise bother me a lot...thank

 

[zzzz]

yes..It is making that sound for me too..

 

[SupermanCK]

it's very annoying when i try to fall asleep with it...so i always have to get up and go switch off the main switch....argh! :|

 

[Viper96720]

Cut off all power to them. If they're plugged in and off voltage is still going in a little. If it's plugged into a surge protector turn that off.