What do I need to know?
Sirens are designed to alert an entire community of danger. Unfortunately, not all sirens are created equal. Different manufacturers make sirens that are tuned to specific frequencies. These tuned sirens often have other tuning options.
Well, they vary from one municipality to another, so if you have trouble locating a sound, check with your local community to find out the specific codes that apply.
What sounds do sirens make? Well, they may not be very exciting on the outside, but sirens are very important parts of our environment. Sirens are constantly being improved upon to provide improved protection for our citizens, while maintaining the same basic sound output.
The most common types of sirens used are:
(1) Single tone sirens
Single tone sirens were developed in the early 1900s to warn of
(2) Double tone sirens
Double tone sirens were developed in the 1950s to warn of
Today, standard signals are 50 volts (watts) and 160 dB(A) and can be programmed to rise or fall according to the
(3)
(4) High or Low noise warning sirens
High or Low sound levels can cause damage to electronic equipment. Equipment manufacturers have often resorted to programming the sirens to high or low noise levels in an attempt to avoid detection. This can be accomplished through the use of audible badges or clasps to the unit. Whelen sirens use a vertical array of dots to designate a level. When a dog detects a danger, it automatically clamps its ears to the
Today, high-low and vertical sound programming are used on sirens, as was the case with German sirens of World War II. This method requires the manufacturer to maintain a register of sounds, which is then used to determine the proper level of force to apply to the siren heads. High-low and vertical sound programs are also used on ambulances, which employ a horizontal array of tones to designate the danger level. Some EuroAmerican sirens also incorporated a
(5) Advisory sirens
An Advisory siren consists of a set of static tones that rotate through 360 degrees. The goal of an Advisory siren is to give the public as much information as possible to help them make informed transportation decisions. The public is encouraged to listen to the Advisory sirens and act as they would any other warning signal.
What sounds do sirens make?
Sirens are made of several materials:
hardened plastics such as hard hats and vests, flexible materials like Plexiglas and Nomex, and electronic devices. The hard materials and flexibility of the flexible ones make them good insulators, so they can be powered from sources such as batteries. Many types of sirens are sold as a unit, such as, “All-Terrain Warning System (ATWS) with 24-hour alert,” which specifies the 24-hour period between 1 a.m. and 5 a.m. (ET) that sirens must be on. Other times (such as 7 days a week), they are activated at noon when schools close (unless otherwise specified by the state) and off during normal business hours (unless otherwise specified by the state).
Most fire sirens are mechanical in design, but some are powered by external sources and incorporate a variety of electronic components to provide enhanced alertness and control. Some fire sirens are linked by radio signals to other sirens in the fire department, for example, to alert firefighters to come help someone. Other designs of fire sirens are “soft” (wiring for electric motors) and “hard” (hardware and electronics for mechanical sirens) to detect and warn firefighters of objects or people (primarily, humans).
Civil defense sirens are often called “sonors” or “sonar” because they picked up the sound of one of two things: a human voice or a rotating disk of metal or plastic between their ears. Theks are tested periodically by sounding each day either once a day or twice a week. The
are Austria, Belgium, Brazil, Canada, Denmark, France, Germany, Ireland, Italy, the Netherlands, Norway, Poland, Portugal, Spain, Sweden and the United Kingdom. The alert is provided by means of a continuous alert signal (often called a “broadcast” signal) through local radio and television. Fire sirens are tested
The Czech Republic, Estonia, Finland, and the Slovak Republic operate sirens to warn of incoming air raids during the morning and afternoon hours.
