best desktop speakers

this may not be the usual question for this forum but i'm looking for reasonably priced desktop speakers for my computers at work. i currently have very inexpensive (10-20 dollar) speakers on each workstation and honestly, for sound quality, they are just fine. this isn't for video/audio editing these are just desktop speakers. the problem i'm having is that since everyone now has cell phones, whenever one rings, the speakers spew this loud almost morse code kind of feedback out of them that's very annoying. i'm assuming it's some kind of shielding issue (or lack thereof). basically, i'm just looking for desktop speakers that don't cost an arm and a leg but won't freak out when cell phones ring.

can anyone point me in the right direction? possibly give me the reason this is happening if you know it or tell me what specifications to look for when shopping. maybe throw a few brands or even specific models. (all these need is a standard stereo speaker connection that would go into any desktop computer...we are currently on PowerMac G5 towers but hopefully within a year or so, will have MacPro's).

thank you