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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 ...
The devices have also been employed to keep marine mammals away from fishing nets. [2] The devices are known as acoustic harassment devices (AHDs) and acoustic deterrent devices, which are smaller AHDs [3] or intended as an awareness tool to warn species to the presence of danger rather than as a tool of harassment at a much louder level. [4]
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 ...
As the saying goes, "good fences make good neighbors," but sometimes, your neighbors are just so damn cool that you want easier access to hanging out with your buddy next door. Thankfully, Natural ...
When the 12 V battery was connected to the system, they experienced one of the first examples of acoustic feedback, [9] a typically unwanted effect often characterized by high-pitched sounds. They then placed the loudspeaker on the laboratory's roof, and claims say that the amplified human voice could be heard 1 mile (1.6 km) away. [ 9 ]
Its distinct tone of urgency, high sound pressure level (123 dB at 10 feet) and square sound waves account for its effectiveness. In Germany and some other European countries, the pneumatic two-tone (hi-lo) siren consists of two sets of air horns, one high pitched and the other low pitched.
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The device works by emitting an ultra-high frequency blast (around 19–20 kHz) that teenagers or people under approximately 20 are susceptible to and find uncomfortable. Age-related hearing loss apparently prevents the ultra-high pitch sound from causing a nuisance to those in their late twenties and above, though this is wholly dependent on a ...