In my childhood I was fascinated by a music car that got triggered when you clapped your hands, and as I grew up, I wondered if we can use the same thing to control lights and fans in a home. My fan and light switches could be operated with a simple handclap rather than walking up to them. As this circuit constantly responds to any loud noise, like a loud radio or my neighbour’s lawn mower, it would often malfunction. However, clap switches can also be fun to build. That is when I discovered this whistle detecting circuit, which detects a whistle. Like speech or music, a whistle has a specific frequency that is constant for a particular duration, thus can be distinguished from other sounds. We'll see how to identify whistles by using a Sound Sensor and an Arduino for this tutorial, and we will use an AC lamp and a relay to control it when a whistle is heard.

As we proceed, we will learn how sound signals are received by devices such as microphones and learn how to use Arduino to measure frequency. This sounds interesting, so let's get started with our home automation project using Arduino.

Arduino UNO Sound Sensor Module Relay Module AC Lamp Connecting Wires Breadboard Sound Sensor Working As we know, the microphone is the part of the sound sensor that converts acoustical vibrations, called sound waves, into electrical energy. An electronic signal is created on an output pin when the microphone's diaphragm vibrates to sound waves in the environment. A microcontroller like Arduino cannot directly process these signals since they are very small in magnitude (mV). The output from the microphone is by default analog, so it is a sine wave of variable frequency, but electronic microcontroller are digital devices and hence can handle square waves better.