Answer: V8 engines
The strongest siren ever built was and remains the Chrysler Air Raid siren. These sirens were manufactured during the Second World War and the Cold War to serve as extremely powerful and far-reaching warning devices for air raids.
How extremely strong? The sirens included a bank of six huge horns connected to a two-stage air compressor and a rotary cutting system powered by a huge FirePower Hemi V8 engine and could produce a siren sound rated at 138 dB at 100 feet . Sirens could be heard at a distance of 20 to 25 km, depending on terrain characteristics. Each siren weighed 2.7 tons, was built on a quarter section of a Dodge truck chassis rail and produced 180 horsepower for siren driving.
If you need an additional idea of the power of the sirens, consider this fascinating tidbit. The US Navy has discovered that it can be used to eliminate the fog of an aerodrome. The pressure of the sound waves was so intense that the water droplets in the air clashed until they were heavy enough to fall in the rain and purify the air.
Federal agencies have funded the installation of these huge mermaids, known as "Big Red Whistles" because of their fire-engine red paint jobs, in cities across America. Although now downgraded, there are still dozens of noisy behemoths hiding on rooftops and towers across the United States – although you might be surprised to find that many of them lack their V8 engines. Most engines of the old Big Red Whistles have ended their lives in custom hot rods.