In the post-WWII era, Chrysler’s first V8 engine was a 331cid destined for use in the 1951 model year. As the Chrysler Firepower engine, it delivered 180hp based on the use of a hemispherical combustion chamber and a compression ratio of 7.5:1.

Gasoline quality was nowhere near what it is today, so this early HEMI was considered a high compression engine. It would see duty through 1955 in the Chrysler lineup, but one of its strangest applications was to power air raid sirens.

The notorious Cold War began shortly after the end of WWII. By 1947, the USSR and the USA disagreed strongly about political principles and the configuration of the post-WWII world. Both parties were completely convinced that the other was bent on world domination.

Major cities had prepared for the possiblity of attack during the war and international tensions made it prudent to maintain a certain level of readiness. Chrysler had been building air raid sirens already, but this one was designed to be the biggest, baddest and loudest ever.

Sure enough. With an output level of 176 dB at the business end, it is the loudest air raid siren ever built. On exit from any of the six output horns, the air is traveling around 400 miles per hour and the signal can be heard from 25 to 30 miles away.

Standing 100 feet away from either, a jet engine at full power barely tops the 138 dB measured from this rig. In audio power terms, that is 30 kilowatts or 30,000 watts. Your little brother’s buddy’s sub isn’t going to handle that!

Thankfully, none were ever used beyond test mode, but if you’re interested in what they do sound like, check out the videos below. Oh wait, turn the volume down first.

Video with Robbie Coltrane and Don Garlits