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An air horn consists of a flaring metal or plastic horn or trumpet (called the "bell") attached to a small air chamber containing a metal reed or diaphragm in the throat of the horn. Compressed air flows from an inlet line through a narrow opening past the reed or diaphragm, causing it to vibrate, which creates sound waves .
An air compressor blows the air into one set of horns, and then it automatically switches to the other set. As this back and forth switching occurs, the sound changes tones. Its sound power varies, but could get as high as approximately 125 dB, depending on the compressor and the horns.
A whistle is a device that makes sound from air blown from one end forced through a small opening at the opposite end. They are shaped in a way that allows air to oscillate inside of a chamber in an unstable way. The physical theory of the sound-making process is an example of the application of fluid dynamics or hydrodynamics and aerodynamics ...
The standard fire alarm sound used in most of North America. Coding refers to the pattern or tones a notification appliance sounds in and is controlled either by the panel or by setting jumpers or DIP switches on the notification appliances. The majority of audible notification appliances installed prior to 1996 produced a steady sound for ...
All foghorns use a vibrating column of air to create an audible tone, but the method of setting up this vibration differs. Some horns, such as the Daboll trumpet, used vibrating plates or metal reeds, a similar principle to a modern electric car horn. Others used air forced through holes in a rotating cylinder or disk, in the same manner as a ...
The event was the first promotional ceremony attended by Police Commissioner Jessica Tisch in her new role as top cop and one insider said the horns left her visibly annoyed.
Videos of eerie noises erupting from the skies have recently surfaced on YouTube, sending people into a panic around the world. The video above shows a particularly frightening episode of this ...
Sound sample ⓘ A civil defense siren is a siren used to provide an emergency population warning to the general population of approaching danger. Initially designed to warn city dwellers of air raids (air-raid sirens) during World War II, they were later used to warn of nuclear attack and natural disasters, such as tornadoes (tornado sirens).