An air raid siren, which is also referred to as a civil defence siren, flood siren, outdoor warning siren or tsunami siren, is usually an electronic or mechanical device, used in order to produce a high degree of sound to warn residents of that area of some kind of lurking danger and in many cases, even indicate the time of day. While most modern sirens are electronic, there are also the hand crank sirens that are still used in some areas today. Here, we bring you information and frequently asked questions on such hand crank sirens.
History of sirens
Originally, sirens had been designed to warn people of air raids during World War II. Then they were also used to warn of natural calamities and nuclear attacks as well. Later, the traditional system started being replaced with more specialized warning signals, such as the Emergency Alert System.
A mechanical siren works with a motor driving a shaft with an attached rotor (also called fan or chopper) to either or both ends. Around each of these rotors is a sort of casing, called a stator, with a number of rectangular holes
The blades draw air and force it out through the slots in the stator, as the plates on the end of the blades interrupts that flow. This produces the deafening sound of the siren.
Modern sirens are capable of generating a sound up to 135 decibels when measured 30 meters away from the siren. Some newer sirens today can even broadcast voice messages over huge regions.
Common questions on hand crank sirens
While it is not really allowed to operate a hand crank siren at home, it is done in some cases. Here are answers to some common questions on hand crank sirens
- Where can I get a hand crank air raid siren?
There are a lot of online sites such as eBay, which features these sirens pretty regularly. They should cost you about $300-$400, depending on the kind of signal you are looking to purchase. Usually, vintage sirens used during WW-II would invite higher bids than most others.
Of course, if you have a lot of money to spare, you can try regular online stores, where you will find the latest models at $1000 plus.
- How loud are air sirens manufactured today?
The American Signal T-135, which is the latest uni-directional signal and also the loudest, gives out a sound of 135 decibels at 100 feet.
- Which is the best electric air raid siren for me?
While eBay does not feature products like these too often, you may look around for second-hand sirens to use for tornado or fire warnings.
Local fire stations also sometimes have an old siren which they may be willing to sell.
Larger sirens generally cost less, as not many want to purchase them. You want to keep it merely for its heritage value, though.
It is better to purchase an air raid siren from proper sellers in case you want it to serve as a real warning system. All the other options will merely help you to purchase a pretty collectible, which may not really come of great use.
- Can I use normal household power for the siren?
While a single-phase siren can work with normal household power, anything more will have to run on a special power unit, as it will consume far more energy.
- Can I legally run an air raid signal from home?
No, you cannot, as you may face a noise ordinance in most areas. Also, it is a crime to use false alarms near nuclear plants and areas prone to tornados. Still, if your land is big enough and your siren is under 70dB, you may consider requesting permission from the authorities.
Note that you will also need proper special earmuffs for protection if you actually intend to use your hand crank siren.