They hum, even when not connected to the sound card. Then the problem is not likely a ground loop, but rather in the speakers' power supply. It'll have to be repaired or replaced.

Logitech has opted to make use of electromagnetic resonance, as opposed to induction charging, to provide power to a static or moving mouse on the Powerplay pad's 275 x 320 mm surface ...

Today, Logitech is changing that with the Logitech G309, an $80 mouse that almost does it all. It’s the first Powerplay mouse this inexpensive, the first with Bluetooth, the first that lets you ...

Logitech has found a legitimate use for wireless charging: the Powerplay mouse pad, which constantly charges your wireless mouse. Your wireless mouse will never again run out of battery.

Logitech, however, could have revealed the perfect solution at E3: the PowerPlay mouse pad, a mat that constantly charges compatible wireless mice.