An air raid siren, also known as a civil defence siren, tsunami siren, flood siren or outdoor warning siren, is generally a mechanical or electronic equipment used to create very loud sound in a particular area which helps in warning the residents of that particular area about expected dangers like flood, tsunami, other natural calamities or any other problem. It is also used, in some cases, to indicate time. In these modern times, hand crank sirens are used only in some areas as electronic sirens are preferred by the locals. I would like to give you some information about hand crank sirens which will surely interest you.
History of sirens
The sirens were first designed during World War II to give warnings about air raids to people. It was also used to inform people about natural calamities and nuclear attacks. As time passed, special warning signals like Emergency Alert Systems were developed to replace the traditional warning system.
A mechanical siren works with a motor which drives a shaft with an attached rotor (also referred to as fan or chopper) to either or both ends. These rotors are covered by a sort of casing called a stator which has many rectangular holes.
The air drawn by the blades in the machine is forced out through the holes in the stator and while the air is being forced out, the plates on the end of the blades interrupt the flow of air resulting in deafening sound of the siren.
Modern sirens can generate sound of upto 135 decibels when measured from the distance of 30 meters from the siren. The advancement in technology has helped in creating sirens which can even broadcast voice messages over a vast area.
Frequently Asked Questions about hand crank sirens
It is generally not permitted to use a hand crank siren at home. Still, in some exceptional cases, it is used. You will find below some common questions pertaining to hand crank sirens.
Where can I get a hand crank air raid siren?
You can buy it online from Amazon or Ebay.
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?
You can use single-phase siren to work with normal household power.
Can I legally run an air raid signal from home?
No, it is not permitted. The local laws, in most cases, prevent you from doing that due to noise pollution laws. Again, it is considered illegal to use false alarms near nuclear plants and areas prone to natural calamities. It is, in some cases, possible to get permission from the concerned authorities who may allow you to use the siren as per the prevalent laws.
You must note that special earmuffs are required for protection of ears if you really intend to use hand crank siren.