Identify brick with internal battery, light and sound I just bought a bulk lot of second-hand bricks and found this odd one inside. It has a black panel on one side and when pressed it plays a screeching sound. Through the transparent purple top I can see two LEDs and a circuit board. 

I'm guessing the battery is so low it can't make them glow and the chop isn't getting enough power to play the real sound. It has the LEGO brand on the bottom so I'm pretty sure it is genuine, but I can't identify the piece or the set it could have come from. 

Once I identify the brick I'll try to find out if it can be opened without breaking it, so I can replace the battery.
This is part # bb0042 : Electric, Light &amp; Sound Siren 4 x 2 x 4 Jack Stone

and here you can hear the sound 

it is from Set 4621-1: Red Flash Station

don't know if the battery is replaceable