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A long-range acoustic device (LRAD), acoustic hailing device (AHD) or sound cannon is a specialized loudspeaker that produces sound at high power for communicating at a distance. It has been used as a method of crowd control , which has caused permanent hearing damage , having an extremely high decibel capacity (up to 160 dB measured at one ...
Ululation (/ ˌ j uː lj ʊ ˈ l eɪ ʃ ən, ˌ ʌ l-/ ⓘ, [1] [2] from Latin ululo), trilling or lele, is a long, wavering, high-pitched vocal sound resembling a howl with a trilling quality. It is produced by emitting a high pitched loud voice accompanied with a rapid back and forth movement of the tongue and the uvula. [3]
The ultrasonic devices achieve high directivity by modulating audible sound onto high frequency ultrasound. The higher frequency sound waves have a shorter wavelength and thus don't spread out as rapidly. For this reason, the resulting directivity of these devices is far higher than physically possible with any loudspeaker system.
The Mosquito or Mosquito alarm is a machine used to deter loitering by emitting sound at high frequency. In some versions, it is intentionally tuned to be heard primarily by younger people. Nicknamed "Mosquito" for the buzzing sound it plays, the device is marketed as a safety and security tool for preventing youths from congregating in ...
A late 19th-century speaking trumpet used by firefighters A small sports megaphone for cheering at sporting events, next to a 3 in (8 cm) cigarette lighter for scale. From the Ancient Greek era to the nineteenth century, before the invention of electric loudspeakers and amplifiers, megaphone cones were used by people speaking to a large audience, to make their voice project more to a large ...
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A siren is a loud noise-making device. There are two general types: mechanical and electronic. There are two general types: mechanical and electronic. Civil defense sirens are mounted in fixed locations and used to warn of natural disasters or attacks.
A crane retrieves part of the wreckage from the Potomac River, in the aftermath of the collision of American Eagle flight 5342 and a Black Hawk helicopter that crashed into the river (REUTERS)