A civil defense siren, also known as an air-raid siren or tornado siren, is a siren used to provide an emergency population warning to the general population of approaching danger. It is sometimes sounded again to indicate the danger has passed. Some sirens, especially within small municipalities, are also used to alert the fire department when needed. Initially designed to warn city dwellers of air raids during World War II, they were later used to warn of nuclear attack and natural disasters, such as tornadoes. The generalized nature of sirens led to many of them being replaced with more specific warnings, such as the broadcast-based Emergency Alert System and the Cell Broadcast-based Wireless Emergency Alerts and EU-Alert mobile technologies.
The Leslie speaker is a combined amplifier and loudspeaker that projects the signal from an electric or electronic instrument and modifies the sound by rotating a baffle chamber ("drum") in front of the loudspeakers. A similar effect is provided by a rotating system of horns in front of the treble driver. It is most commonly associated with the Hammond organ, though it was later used for the electric guitar and other instruments. A typical Leslie speaker contains an amplifier, a treble horn and a bass speaker—though specific components depend upon the model. A musician controls the Leslie speaker by either an external switch or pedal that alternates between a slow and fast speed setting, known as "chorale" and "tremolo".
A fire alarm notification appliance is an active fire protection component of a fire alarm system. A notification appliance may use audible, visible, or other stimuli to alert the occupants of a fire or other emergency condition requiring action. Audible appliances have been in use longer than any other method of notification. Initially, all appliances were either electromechanical horns or electric bells, which would later be replaced by electronic sounders. Most of today's appliances produce sound levels between 70 and 100 decibels at three feet.
A siren is a loud noise-making device. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks. Sirens are used on emergency service vehicles such as ambulances, police cars, and fire engines. There are two general types: mechanical and electronic.
An air horn is a pneumatic device designed to create an extremely loud noise for signaling purposes. It usually consists of a source which produces compressed air, which passes into a horn through a reed or diaphragm. The stream of air causes the reed or diaphragm to vibrate, creating sound waves, then the horn amplifies the sound making it louder. Air horns are widely employed as vehicle horns, installed on large buses, semi-trailer trucks, fire trucks, trains, and some ambulances as a warning device, and on ships as a signaling device.
A fire alarm system warns people when smoke, fire, carbon monoxide, or other fire-related or general notification emergencies are detected. These alarms may be activated automatically from smoke detectors and heat detectors or may also be activated via manual fire alarm activation devices such as manual call points or pull stations. Alarms can be either motorized bells or wall-mountable sounders/horns. They can also be speaker strobes that sound an alarm, followed by a voice evacuation message for clearer instructions on what to do. Fire alarm sounders can be set to certain frequencies and different tones including low, medium, and high, depending on the country and manufacturer of the device. Most fire alarm systems in Europe sound like a siren with alternating frequencies. Fire alarm electronic devices are known as horns in the United States and Canada and can be either continuous or set to different codes. Fire alarm warning devices can also be set to different volume levels.
Wheelock is a fire alarm and general signaling products manufacturer owned by Eaton Corporation.
A train horn is an air horn used as an audible warning device on diesel and electric powered trains. Its primary purpose is to alert persons and animals to an oncoming train, especially when approaching a level crossing. They are often extremely loud, allowing them to be heard from great distances. They are also used for acknowledging signals given by railroad employees, such as during switching operations. For steam locomotives, the equivalent device is a train whistle.
Federal Signal Modulators are electronic warning devices produced by Federal Signal Corporation that are used to alert the public about tornadoes, severe weather, earthquakes, fires, lahars, tsunamis, or any other disaster. They are identified mostly by their distinctive stacked "flying saucer" design. The Modulator II is sold based on the more compact chassis of the siren compared to the original Modulators.
The Chrysler Air Raid Siren, or known as the Chrysler Bell Victory Siren is an outdoor warning siren produced during the Cold War era that has an output of 138 dB(C) at 100 feet (30 m).
The Whelen Engineering Company is an American corporation that designs and manufactures audio and visual warning equipment for automotive, aviation, and mass notification industries worldwide. Founded in a Deep River, Connecticut garage in 1952, Whelen has become a provider of warning lights, white illumination lighting, sirens, and controllers. Whelen products are designed, manufactured, and assembled in two facilities in Chester, Connecticut and Charlestown, New Hampshire.
The Mount Rainier Volcano Lahar Warning System consists of two separate components, operating in tandem: Acoustic Flow Monitors (AFM) and the All Hazard Alert Broadcast (AHAB) sirens. The AFM system was developed by the United States Geological Survey (USGS) in 1998 and is now maintained by Pierce County Emergency Management. The purpose of the warning system is to assist in the evacuation of residents in the river valleys around Mount Rainier, a volcano in Washington, in the event of a lahar. Pierce County works in partnership with the USGS, the Pacific Northwest Seismic Network (PNSN), Washington Military Department's Emergency Management Division, and South Sound 9-1-1 to monitor and operate the system.
American Signal Corporation (ASC) is an outdoor warning siren and mass notification company in the United States. ASC was founded in 1873 as Biersach and Niedermeyer (B&N). After performing poorly, the company reformed as The Alerting Communicators of America (ACA) in 1968 and expanded the line of warning systems they produced. In 1992, ACA went bankrupt and was bought and reformed as the American Signal Corporation.
The ATI Soundblaster HPSS is an electronic outdoor warning siren manufactured by Acoustic Technology, Inc that is used to alert citizens of tornadoes, hurricanes, severe thunderstorms, fires and so on. The recent HPSS systems use high-powered electronic speakers, which can be independently arranged to provide directional or omnidirectional coverage, depending on installation. The HPSS16 have 4 speakers and the HPSS32 have 8 speakers. They can also be used as public announcement (PA) systems, and can play a number of programmed tones. Options include solar-powered operation pre-recorded voice messages. ATI also sold rotational units of the HPSS16, and HPSS32, called the "HPSS16R" and "HPSS32R", that are now discontinued.
A horn is a sound-making device that can be equipped to motor vehicles, buses, bicycles, trains, trams, and other types of vehicles. The sound made usually resembles a "honk" or a "beep". The driver uses the horn to warn others of the vehicle's approach or presence, or to call attention to some hazard. Motor vehicles, ships and trains are required by law in some countries to have horns. Like trams, trolley cars and streetcars, bicycles are also legally required to have an audible warning device in many areas, but not universally, and not always a horn.
The Public Warning System (PWS) is a network of civil defense sirens installed by the Singapore Civil Defence Force on over 2,000 strategic points in Singapore to warn Singaporeans of impending dangers, air raids and atomic bomb blasts. Thus far, the siren network has only been used for occasional public awareness drills, monthly noon chimes and for commemorating the island's Total Defence (February 15) and Civil Defence Days (September 15). It was also used to mark a minute's silence nationwide for the passing of former prime minister Lee Kuan Yew on the evening of 23 March 2015 and on 1 and 9 August 2020 to mark the first National Day at home.
The Federal Signal Model 2 is an omnidirectional outdoor warning siren produced by Federal Signal Corporation.
The Thunderbolt is a discontinued mechanical outdoor warning siren made by Federal Signal Corporation. It has a very recognizable design, being a unidirectional siren with a large yellow exponential horn.
