I used to have a problem trying to wake up to my alarms so I tried to think of something that no one could sleep through. How about an air raid siren?

The Alarm Clock

On Aliexpress, I found a small 12V air raid siren which upon second viewing, is probably intended for cars but for what purpose I don’t know. Regardless, I found that the iconic British WWII Blitz airstrike warning signal uses a 2-tone sound created using sirens in pairs. So I bought 2.

I designed very minimal additional 3D printed pieces to house the equally minimal electronics inside. Power was routed in through a DC barrel jack on the other side. A voltage regulator brought down the 12V input to 5V for the ESP32; the ESP32 controlled a relay that switched the 12V sirens. To cut down on hardware, instead of a display and buttons, the alarm time could be set via a webpage hosted by the ESP32.

It was much too loud to use and I did not need to give the neighbors another reason to hate me. Eventually, I ended up gutting the project for parts but it was a good proof of concept. I’ve also since lost the Arduino code but the next time I attempt another clock project, I’d prefer to use a physical display and controls instead of a web interface.

Long-Range Acoustic Device

As for the sleeping through alarms problem, I came across Tech Ingredient’s video on LRAD. It’s an acoustic weapon designed to focus sound at human targets to overwhelm their ears. While the system can play any sound, a “chirp” that sweeps every frequency is often used; it has a lot of advantages but I find that it’s incredibly hard to ignore at any volume. No longer do I have to worry whether my phone volume is set too low. The higher pitches of the chirp are able to cut through the deepest of sleeps without being loud enough to wake my family sleeping in the other rooms. The only reason I miss my alarms now is if I forget to charge my phone (disappointing on multiple levels).

Have a listen and try using it as an alarm sound for yourself!