What is this weird interference between my phone and my computer speakers?

I keep my cell phone near my computer speakers whenever it’s not with me and I’ve found that the computer speakers make a static sound right before the phone shows that I’m recieving a call or a text. The speakers sometimes make the sound in a short burst without reason but not nearly as noticeably. Finally, when I moved the mouse on my old computer and volume at max there was a static sound when I moved it. I have a Verizon Dare and standard Dell speakers. Overall, I’m just wondering if anyone can explain exactly whats going on. Any ideas?

Sorry about the long details and thanks in advanced.