Those plastic shells contain Ferrite choke beads whose presence is to reduce radiated emissions which cause EMI/RFI interference. The clock frequency and many harmonics radiate from your "noise generator laptop". Also, fast switching creates radiated transients. Digital equipment can radiate some nasty interferring signals, all of which find themselves in the middle of a frequency range somewhere, almost always used by a radio receiver of some type.

Those shielded and choked cables not only keep RF energy radiating from your computer, it can also keep the creepy crawly stuff from entering it from a nearby broadcast transmitter.

Google words: RFI, ferrite, choke