Who could watch the Bionic Man, Bionic Woman, Daredevil, Spider-Man or any other superhero without longing for their enhanced super senses? With a little money and a little time, the gift of super hearing--or at least enhanced hearing--can be yours, thanks to homemade hearing devices.
A Parabolic Mike
Turn a 30-inch plant aquarium into a parabolic mike and listen to the wealth of noises outside your window previously undetected. Secure the dish to a pole with duct tape and wires. Determine the placement of the main mike by placing a small, round makeup mirror in the bottom of the dish. Aim it toward the sun and mark the position of the reflection on the pole. Attach the main mike over the mark on the inside of the dish so that the end of the mike that detects sounds is pointed toward the dish's inside; rubber bands and duct tape work well for this purpose. Mount two stereo mikes near each other with one mike facing the inside of the dish and the other mike away from the dish. Wire the mikes to your stereo so you can record what the mikes catch.
Take a 8 1/2-by-11-inch sheet of paper. Roll it into a funnel shape, lengthwise, so one end is about as large as a dime while the other is significantly larger. Tape the paper so that the funnel shape is maintained. Place the smaller end of the funnel shape near your ear and listen. Thanks to the large opening on the bull horn, more sound waves are collected than would be normally possible by your ear alone. Do not, however, insert the small end of the funnel into your ear. According to Reeko's Mad Scientist Lab (see References), this can cause the funnel to get stuck inside, which, while improving one's hearing immeasurably, prevents one from easily passing through doors.
Take apart two multi-media microphones and remove the small mikes from the housing, but be careful to keep the mikes attached to the 3.5-mm stereo wire and plugs. Take the earpieces from the stethoscope and carefully drill out the interior of the plug so they can accommodate the mikes. Put some hot glue inside the ear plugs and insert the mikes, then put the ear plugs back on the stethoscope. Plug the mini jacks from the mikes into a Y adapter, which plugs into your MP3 player or recorder. Now you will be able to record what you hear.