speaker interference

after adding cable modem, wireless router, usb wireless nic’s, and a usb wireless print server, i now have a constant “tapping” noise in my 5.1 surround sound speakers. a radio tech told me it’s from the coax cable, but i suspect the 802.11g gear. all the components are relatively close to each other, exc one nic in an adjacent room. your thoughts pls. tks.