Chrysler's Cold Warrior- or the loudest air-raid siren ever produced

[Haasman]

In case you missed this August 2013 Autoweek article- Quite amazing .....
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Chrysler's Cold Warrior

When Hemi power safeguarded American cities
Andrew Stoy 9:30 am, August 8, 2013
Viewed through the lens of 1950s communist paranoia, a 3-ton, 12-foot-long, V8-powered air-raid siren probably made a perverse sort of sense.
After all, civil-defense doctrine claimed Soviet bombers lumbering over the North Pole would offer enough lead time to at least notify urban populations of impending atomic incineration. All that was needed was a device able to alert a large swath of the public as quickly as possible.

Enter a uniquely American solution: the Chrysler Air Raid Siren.
Like so many engineering milestones, the siren's genesis was a product of war-time urgency: In the early 1940s, the Office of Civil Defense brought Chrysler and Bell Labs together to create a warning device capable of alerting full cities in the event of a Japanese or German surprise attack. Hundreds of conventional electric sirens could be used, but OCD wanted a machine with unprecedented range, minimizing the number that would have to be installed to warn a given population.

The result, known initially as the Chrysler-Bell Victory Siren, coupled a 140-hp Chrysler inline eight-cylinder gasoline engine with a two-stage air compressor and rotary chopper. The chopper was a rotating slotted disc that sliced the air into pulses to create sound; it was then directed through six horns. The output was a staggering 137 dB at 100 feet -- Top Fuel drag-race loud.

To spread the sound across the largest radius possible, the assembly rotated through a chain-driven turntable powered via a gear reduction system. With the engine at its approximately 3,200-rpm operating speed, the siren rotated at 2 rpm.





Cold-War-era-Hemi-powered-Chrysler-air-raid-siren.jpg


According to Chrysler company records, approximately 350 Hemi-powered air raid sirens were built.

While the Chrysler-Bell siren achieved its acoustic goals, its other specs were not quite as advanced: The first production models were manually controlled. A seat was provided, requiring a single brave soul to climb aboard the monstrosity, Slim Pickens-style, rotating until the nuclear flash relieved both man and machine of duty.

Aware of the design's limitations, a final improved siren was introduced as the Chrysler Air Raid Siren in 1952. Up-grades included the use of the then-new 180-hp, 331-cubic-inch Chrysler Hemi engine and a three-stage compressor to increase output. The operator's seat was also gone, replaced by a control panel on the siren's side allowing dedicated phone lines to activate it. The device was also now even louder, rated at 138 dB at 100 feet.

The Chrysler Air Raid Siren remains the loudest siren ever produced. Its remarkable specifications include a compressor discharge volume of 2,600 cubic feet per minute at 7 psi and a residential coverage area of approximately 16 square miles. In comparison, the electric sirens commonly used today for tornado and tsunami warnings can alert about four square miles.

According to company records, approximately 350 Chrysler Air Raid Sirens were built, all by the company's Marine and Industrial Engine division in Trenton, Mich. A handful remained in service as late as the 1970s, then were scrapped. Some were acquired by museums -- including the now-defunct Walter P. Chrysler Museum in Auburn Hills, Mich. -- or fell into the hands of ambitious collectors.

Fewer still were simply left in place, the cost of removal outweighing the visual pollution. One example remains at the edge of a West Hollywood public park. Another sits on a bluff overlooking Glendale, Calif. Caked in pigeon droppings and, in at least one case, missing its engine, these rusting hulks are a reminder: At one point, even the apocalypse had a Hemi.

source http://www.autoweek.com/article/2013...ws01/130809890

[dummkopf]

Cool stuff. I wonder how many of the operators suffered hearing damage. I've seen one of the Hemi power sirens operate. I wanted one for some reason.

[Haasman]

I hope not too many. My guess at those db levels the human body simply can't tolerate it too long, let alone ears and hearing.

This is from WebMD

Harmful Noise Levels

The effects of noise on hearing vary among people. Some people's ears are more sensitive to loud sounds, especially at certain frequencies. The frequency of a sound determines how low or high a tone is. But any sound that is loud enough and lasts long enough can damage hearing and lead to hearing loss.
A sound's loudness is measured in decibels (dB). Normal conversation is about 60 dB, a lawn mower is about 90 dB, and a loud rock concert is about 120 dB. In general, sounds above 85 are harmful, depending on how long and how often you are exposed to them and whether you wear hearing protection, such as earplugs or earmuffs.

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Following is a table of the decibel level of a number of sounds.

Leaves rustling, soft music, whisper	30
Average home noise	40
Normal conversation, background music	60
Office noise, inside car at 60 mph	70
Vacuum cleaner, average radio	75
Heavy traffic, window air conditioner, noisy restaurant, power lawn mower	80-89 (sounds above 85 dB are harmful)
Subway, shouted conversation	90-95
Boom box, ATV, motorcycle	96-100
School dance	101-105
Chainsaw, leaf blower, snowmobile	106-115
Sports crowd, rock concert, loud symphony	120-129
Stock car races	130
Gun shot, siren at 100 feet	140

As loudness increases, the amount of time you can hear the sound before damage occurs decreases. Hearing protectors reduce the loudness of sound reaching theears, making it possible to listen to louder sounds for a longer time.
An easy way to become aware of potentially harmful noise is to pay attention to warning signs that a sound might be damaging to your hearing. A sound may be harmful if:

• You have difficulty talking or hearing others talk over the sound.
• The sound makes your ears hurt.
• Your ears are ringing after hearing the sound.
• Other sounds seem muffled after you leave an area where there is loud sound.

Most cases of noise-induced hearing loss are caused by repeated exposure to moderate levels of noise over many years, not by a few cases of very loud noise. Wearing hearing protectors can help prevent damage from both moderate and loud noise.
If your workplace has harmful noise levels, plan ahead and wear hearing protection. People who may be regularly exposed to harmful noise because of their jobs include:

• Those who work with loud machines, vehicles, or power tools, such as construction workers, factory workers, farmers, truck drivers, mechanics, or airport ground crew workers.
• Military personnel.
• Police officers and firefighters.
• Musicians.