Shielded cable, eg. coaxial, usually stops external interference, but that poses a slight problem with wiring to your spkrs. There is other shielded cable for spkrs, but the best thing is to track down the source of the interference and move it, or fix it (eg. arcing inside some device nearby).
[In my case it was a bare hard drive in close proximity to and on the same power circuit as my audio amplifier. As changing things around was more trouble than help, I tolerate the occasional nuisance.]