I put both my iPod nano and cellular phone (Nokia 6230) in my shirt pocket. I noticed on several occasions that if I received an SMS the volume of my iPod suddenly was turned down. Has anybody noticed this? I don't know whether this is by design (a feature?) or an accident (a bug). In one occasion I cannot control the volume after that (the respon was slow). So, I am assuming that this was not by design. I even affraid that this could harm my iPod in the future. Good thing the volume is turned down not up! Otherwise I would hurt my ears.
How does it work, anyway?
Why is it happening?
Can electromagnetic wave effect the volume of my iPod?
I want to know the physics (theory) behind it. Hints?