iPod Erm, stupid question

I've noticed that every time I go through the security gate at the library of the hospital I work in, I hear a faint, high-pitched whine. I put two and two together quickly and realized it was the iPod that was responsible. I don't know how those gates work except I sort of figure that if the security device is magnetic, the gates are checking for a certain...polarity? Or something. I really don't know magnets. So assuming this is the case, I figure it must be the battery that causes that noise.

I don't imagine there's any harm in this, really, but I just wanted to make sure--it's not going to do damage, is it?

So...should I turn it off? Would that matter? I mean, I'm over there for 4 hours for a shift and bring it with me for the walk there, the walk back, and the time I'm there. I can't imagine it's too damaging because...I mean, people with pacemakers have to shop, right? And how do you get a purchased computer through the security gates without killing it?