Machine gun pulse
This project is a pulse oscillator that has a sound like a machine gun or a one cylinder motorcycle engine. Adjust the control volume to change the sound from the speaker from a few pulses per second to a dozen or so per second.
After wiring this project, turn power ON and press S1. You can experiment and change the frequency of this oscillator by trying other capacitors in place of the 10µF capacitor. Be sure to observe the + and - connection (polarity) on the capacitors marked with a + sign.
Don't forget you can change the frequency by adjusting the control volume, too!