06-08-2009 04:40 PM
It is most likely a interference with hardware inside the laptop. These types of speakers were really meant to be used on a desktop.
You know how you can connect headphones to a computer and you will hear all these little weird electronic noises. It's the same thing as that.
06-08-2009 04:59 PM
06-09-2009 08:28 AM
The USB external sound cards should help in this regard.
In general, onboard motherboard audio (whether desktop or laptop) tends to have excessive noise.
Regarding USB vs. ExpressCard - for audio purposes (even 5.1), the bandwidth USB provides should be more than enough. In fact, I wouldn't be surprised if that ExpressCard uses a USB interface internally (ExpressCard slots may use either PCI Express or USB for the actual electrical interface.)