It’s been a while since I posted an evil science project, so this one is to make a parabolic listening device. I recently saw a poeject where someone made a parabolic microphone from a $2 plastic umbrella and a bunch of other things from the cheap store. The problem with the umbrella is that the dish area is not entirely rigid and the amount of sound reflected to the micorphone is reduced because of this. Whats needed is a hard metal surface. You could sneak over next door and unbolt your neighbours TV dish. But no, for this project we are going to use kitchen cookware and create the Spy Wok 9000.
For this project you will need: a wok (get the old school kind with handles ether side); fisinging line or strong string; thin dowel or metal tube; a lapel microphone; headphones; a recorder (not the musical flute kind); some duct tape.
If you don’t have a wok you’ll have to go purchase one at the chinese grocery store. Be careful not to act suspicious in case the store attendant is an informant. Most of the other things you can get almost anywhere, but remember to wear sunglasses when you buy them so you can’t be identified later.
Tie the fishing line or string diagonally between the handles, you want two strands each diagonal. Its fine to use one long continuous strand looped around for the entire lot. Where they cross will be in the centre of the wok. You can do some fancy over under type weaving to make it more secure if you are so inclined. Spread the string where it all crosses and place the rod in the middle (Diagram 1).
Next you need to find the distance the microphone needs to be from the dish. If your wok is shiny you could use a laser pointer and see where the beam reflects most on the shaft. Alternatively you could do it by ear with the Wok Awound the Clock method. Put a ticking clock on the far side of the room, point your wok at the clock and slide the microphone laong the shaft untill you find the best point on the shaft it collects the sound. It will work better if you use headphones.
Cut the shaft to length. Secure the shaft to the wok with a hot glue gun. If you think your wife might get mad at you for this, you could use a bit of chewing gum like MacGyver so she won’t get suspicious. My wife is Chinese and whenever I’m trying to explain myself she gives me suspisious, sideways, slanty eyed looks. She could be a spy. Alternatively you could try using some sticky rice because it is a wok after all. Attach the mocrophone to the shaft with the tape and while youre at it tape the microphone chord to one of the lengths of string. Plug it all in and you are ready to wock and woll with your Spy Wok 9000 (Diagram 2).