Hi all.
I have a 2004 Civic hatchback, and a little while back I discovered a high pitched sound coming from the back of the car. Funny thing is, the sound is there even with the ignition off!
After a little searching I found a little box behind a panel at the back of the boot right side, containing a circuit board with a bunch of wires attached (soldered), and another bunch of wires attached by tightened screws.
When disconnecting the battery, the sound first rises in pitch then dies off. Attaching the battery, and the sound is back.
A friend suggested it might be a backing/parking sensor, but I've not seen any sign of that since I bought the car 2 years ago.

Also, while exploring, I managed to dislocate the wires that were fastened by screws. Not sure where to attach them. This did nothing for the sound.
I've attached a video- I'm sorry for the quality, at least you get an impression of the sound.

Video

Edit: After tearing away more panels, I've come to the conclusion that the circuit board is for the tail lights.

Edit: Some images. Sorry for bad light and shaky hand

 

So the circuit board you found is all soldered, not possible to disconnect it?

 

5 of the wires are soldered, 5 are fastened with screws. ATM 4 are loose, because I don't know which wire goes where.
I wrote Honda in my country about this issue, but no reply yet. I'd hate to write the official Honda importer, as they are, how can I put this diplomatically, difficult to deal with when it comes to parts.
It seems some of the wires goes to lights. But the speaker on the circuit board, which makes the nerve rattling sound, puzzles me. Why would a connector board for the lights have a speaker?