So, having speakers at my desk isn't really useful because I share an office. We're headphone users around here. So, I just use one speaker - the one with the headphone jack in it - that I keep around as a volume control. Little did I know when I installed this thing that it would also be serving as my personal microwave radiation sensor. That's right. See, when my cell phone talks to the network every half hour or so. These mysterious communications produce enough EM radiation to induce noise in my speaker... not just quiet background crackling either. I mean some serious structured, Morse-code-ish, bursts of buzzing static! Funny thing is that it doesn't do this while I'm actually talking on the phone... just before, or at regular intervals throughout the day. I speculate that it's using a high-power signal to make itself known to all of the cell towers in range so that it can switch to the one most appropriate for giving me barley acceptable quality of service.
On an interesting tangent, the office on the other side of the thin wall in front of my desk is occupied by a guy with a loud phone voice. One of those people who unconsciously double in volume when they're talking on the phone. Well, my speaker can also detect incoming calls for his cell phone too. It's like an early warning system. *BZZZZZZzzzzzzzzzzzzzzzt* then moments later, “Hello? Blah blah blah...”