Make sure you use the volume knob judiciously. It acts as sort of a squelch, as well. Experiment and have fun.
What else can you use it for?
The high-gain amplifier I designed in this project is ideal for a variety of eavesdropping ventures.
- Replace the piezo mic with six to eight turns of 26-gauge magnet wire wound in a 3x5 foot loop and you can hear atmospheric noises such as lightening, the wind, even distant auroras can be heard with a high-gain amplifier.
- Replace the piezo mic with a 100-turn coil of 28-gauge magnet wire around a ferrite core and you can hear the wires buzzing in the walls and locate hidden wiring. If you place a magnet at 40 degrees to the coil, you can hear nails under the plaster or sheet rock.
- Replace the piezo mic with a single loop connected to a diode and you can detect RF signals and use the high-gain amp as a "bug" detector.
- Connect a solar cell in place of the piezo mic and you can "hear light." Point it at an airplane in the sky and you can hear it's strobe. POint it at any light that has something periodically passing through it like a propeller or a rotary shaft, and you can hear the device.