iPhone causing interference with my iPod!

Had a strange thing happen today. You know when the iPhone is transmitting data and it is near computer speakers you may here some interference coming out of the speakers? Kind of like morse code? My phone does this all the time when I'm at work and it is near my office phone. I've witnessed blackberry's do the same thing near speaker phones.

Anyway, I was listening to my 5th Gen iPod today, both iPod and iPhone were on my desk next to each other. I get an incoming call from "UNKNOWN" so I just hit the cancel button on top and lay the phone back on my desk when the volume on my iPod went way up! I normally listen at around 50%, I'd say it went up to 75%. I picked up the iPhone and moved it near and far from the iPod over and over. Sure enough the volume on the iPod would go up and down. The level of volume didn't necessarily match the distance I had the phone from the ipod but it was clearly being interfered with by the phone.

Eventually the call/data transmission ended and the interference stopped. The volume on my iPod ended up being at around 25% and I had to reset it. Very strange, I would have expected to hear some interference through the speakers, but NOT actually changing the volume on my iPod!