The most mysterious thing I've seen in a long time.

[teh_blumchenkinder]

(Snip)
I take out the batteries, and the noise doesn't stop.
(snip)

... and it stopped when you dropped it in water.
Sounds like a ghostie to me!
At least it was just the radio. Maybe something was trying to talk.
It's entirely possible that it's a type of radio that power bums around in it for an amount of time after it's disconnected, but I usually only see that with high-voltage/ very dangerous stuff, like generators. Three or four seconds you say? I had a monitor that did that, but it was really over-powered/ over-zealous.

[telecom_goddess]

Uhm...if this happened to me, I would probably crap my pants. And then I would go running for my parents and a priest.

Yeah me too damn...

[firecat88]

Yeah me too damn...

I may or may not have unplugged my radio last night before going to bed. Given the weird stuff that's been happening at my house lately, I wouldn't put it past some entity to get into my room long enough to pull some kinda crap like that before they get caught and pummeled.