What you hear at the start of this video is the sound of a Chrysler FirePower Hemi V8 engine start and rev-up. Afterwards comes the old familiar wail of the cold war nuclear attack warning.
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).
The main purpose of the [‘Big Red Whistle’] 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. – SuzukiBlaze
When the Chrysler Air Raid Sirens were being retired during the 1970’s a number of car enthusiasts sought out the Hemi V8s for use in bracket racing and street rods.