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How Clap Lights Work

Melissa Wiese on Flickr

Did you ever turn a light on and off by clapping your hands? Maybe you’ve seen this on TV or in a movie where the characters live in an expensive high tech house. But, this technology isn’t just for the rich and famous. It’s entirely possible to buy, or even make, a device that turns your lights on and off when you clap. Let’s look into how that works.

A clap-activated light isn’t too different from regular switch technology in terms of electronics, except it relies on claps instead of flipping a switch. So that bit is easy peasy. But how do you get a device to detect a clap? You can’t program to just detect any sound, otherwise everything from footsteps to keyboard taps will trigger the lightswitch. It would be awfully hard to focus or relax with lights blinking on and off at every sound.

So, there needs to be a way to differentiate between a clap and everything else. You can do that by analyzing the sound waves that a clap gives off and then telling the microphone in the light switch to look out for those types of waves.

Clapping sounds are pretty unique because they’re both loud and pretty high-pitched. We can measure the loudness by using decibels, and the pitch with its wave frequency measured in hertz. A clap from 1 meter away is 130 decibels and hits around the 2200 to 2800 hertz range.

While clap sounds are not that frequent in the course of a regular day. So, similar sounds like small dog barking or someone popping bubble wrap may also trigger the sound detector. As such, the next challenge is to make it so that the device knows when someone is clapping, and when something sounds like a clap.

Tightening up the sound detection may be a good solution, but no two claps sound identical. As such, if you make the sound detection too strict, the device may ignore legitimate claps which would be really frustrating.

The solution that some audio engineers use is to listen for two or three claps in a short space of time. Sure, a dog barking or some bubble wrap popping may sound like a clap, but they typically don’t happen twice in the space of a second. Meanwhile, it’s easy for someone to clap twice quickly.

As such, the end product is a little device that listens out for two or three claps in short succession. It’s by no means perfect, but it does provide a way for people to clap their lights on and off without a barking dog turning the whole house into a light rave!

Learn More

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