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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 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 ...
The first squeaky toys were simple rubber balls which produced a high pitched noise when air was squeezed through a hole, without a special noise maker. Later examples contained a metal noisemaker known as a "whistle disk." Brightly colored rubber squeaky toys molded in various shapes became common during the 1940s.
High-amplitude sound of a specific pattern at a frequency close to the sensitivity peak of human hearing (2–3 kHz) is used as a burglar deterrent. [ 6 ] Some police forces have used sound cannons against protesters, for example during the 2009 G20 Pittsburgh summit , [ 7 ] the 2014 Ferguson unrest , [ 8 ] and the 2016 Dakota Access Pipeline ...
In most horns it also determines the pitch of the sound. When vibrated by the diaphragm, the column of air in the horn vibrates in standing waves. The length of the horn determines the wavelength of the sound waves generated, and thus the fundamental frequency (pitch) of the note produced by the horn. The longer the horn, the lower the pitch.
In a pneumatic siren, the stator is the part which cuts off and reopens air as rotating blades of a chopper move past the port holes of the stator, generating sound. The pitch of the siren's sound is a function of the speed of the rotor and the number of holes in the stator. A siren with only one row of ports is called a single tone siren.
Blowing pressure – Sound level increases as blowing pressure is raised, [59] [60] although there may be an optimum pressure at which sound level peaks. [48] Aspect ratio – Sound level increases as whistle length is reduced, increasing frequency. For example, depressing the piston of a variable-pitch steam whistle changed the frequency from ...
A noisemaker is something intended to make a loud noise, usually for fun. Instruments or devices commonly considered "noisemakers" include: pea whistles; air horns, composed of a pressurized air source coupled to a horn, designed to create an extremely loud noise; fireworks, such as firecrackers, bottle rockets, bang snaps and others