Loudest warning siren could be heard from a distance of 20 to 25 miles

The loudest outdoor warning siren ever produced was the Chrysler Air Raid Siren, which could be heard from a distance of 20 to 25 miles and was powered by a Hemi V8 engine

The Chrysler Air Raid Siren (second generation), or known as the Chrysler Bell Victory Siren (first generation) was an outdoor warning siren produced during the Cold War era that had an output of 138 dBC at 100 feet (30 m).

Built during the World War II and Cold War era from 1952-1957 (second generation) by Chrysler, its power plant contained a newly designed FirePower Hemi V8 engine with a displacement of 331-cubic-inch (5.42 l) and producing 180 horsepower (130 kW).

Its six horns were each 3 feet (0.9 m) long. The siren could be heard from a distance of 20 to 25 miles (32 to 40 km) away and had an output of 138 dBC (30,000) watts. They were 12 feet (3.7 m) long, built atop a quarter section of a Dodge truck chassis rail, and weighed an estimated 3 short tons (2.7 t).

In 1952, the cost of a Chrysler Air Raid siren was $5,500.00. (Approximately $43,966.48 in 2009 dollars.) The United States government helped buy sirens for selected state and county law enforcement agencies around the country. In Los Angeles County, six were placed around key locations of populated areas, and another ten were sold to other government agencies in the State of California. These “Big Red Whistles” (as they were nicknamed) were only ever used for test purposes. Some were located so remotely that they deteriorated due to lack of maintenance.

The main purpose of the siren was to warn the public in the event of a nuclear attack by the Soviets, during the Cold War. The operator’s job was to start the engine and bring it up to operating speed, then to pull and release the transmission handle to start the wailing signal generation. The Chrysler air raid siren produced the loudest sound ever achieved by an air raid siren.

Some sirens are still located above buildings and watchtowers. However, many of these are rusted, and in some cases, the salvage value is less than the cost to remove them. A majority of these sirens have been moved to museums. Some of them have been restored to fully functioning condition.