Last Updated: 16 Jan 2016
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In these two videos, I do a quick desktop demo of playing a siren sound through first a "fixed frequency" car horn, and then through a standard car audio speaker, rated at 120W peak, 60W RMS, and 4 Ohms. Using an Arduino, a relatively simple, custom transistor-based amplifier circuit, and the Arduino core tone() function in my code, I drive the horn and speaker to play a siren sound by sinusoidally varying the driving frequency. I also show the signal to the devices on an oscilloscope, and briefly discuss and hook up a Schottky diode in a "snubber diode" configuration to knock down the inductance-induced voltage spikes created each time the square wave has a falling edge.
First, watch the "fixed frequency" type car horn play a varying-frequency siren sound: