As a kid I was fascinated by a toy music car which gets triggered when you clap your hands, and then as I grew up I wondered if we can use the same to toggle lights and fans in our home. It would be cool to just turn on my Fans and lights by just clapping hands instead of walking my lazy self to the switch board. But often times it would malfunction as this circuit will respond to any loud noise in the environment, like a loud radio or for my neighbor’s lawn mower. Although building a clap switch is also a fun project to do.

It was then, when I came across this Whistle Detecting method in which the circuit will detect for whistle. A whistle unlike other sounds will have a uniform frequency for a particular duration and hence can be distinguished from speech or music.