The Glass Ear
I use this to listen to what is happening inside a room. The key to this is the piezo buzzer. This is like a speaker, but it creates vibrations in an object instead of the air like a speaker. Speakers vibrate air, piezo buzzers vibrate objects, get it? You can plug a pair of headphones into a microphone input and use them backwards, as a microphone. You can plug a piezo buzzer into the same microphone input and use it as a vibration, or contact, microhpne. This will amplify and vibrations that the window feels, mainly someone’s voice and other room noises. This works great on a glass window. Piezo buzzers are fun to play with. They are cheap, but also found in many toys.
- piezo buzzer
- old headphones
- portable cassette player
- electrical tape
- wire cutters
- wire strippers
1. Sometimes piezo buzzers are surrounded in plastic. Use the wire cutters to cut the plastic away. They usually have a hole in the center of the buzzer. Start cutting there. Be careful. These things can be fragile.
2. Cut your headphones wire. You are going to use the end that has the 1/8th inch plug. Make sure you give yourself a long enough wire by cutting near where the wire splits and goes to each headphone. Strip the coating away to expose each wire.
3. Twist the together each one of the wires from the piezo buzzer to a wire from the headphones. Make sure that your twists don’t touch each other. Use electrical tape to cover each connection.
4. Tape the flat side of your piezo buzzer against the window.
5. Plug your headphone jack into the “microphone in” on your portable cassette player or stereo system. Start with the volume very low, and then raise it as needed.
Once completed, don't forgot to print out your detective badge and start solving crimes in your town.