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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. In some versions, it is intentionally tuned to be heard primarily by younger people.
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 ...
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.
HoMedic’s alarm clock offers eight relaxation and nature sounds— including a white, pink, gray and brown noise option. The “sleep therapy” options play your favorite nature sound for 15 or ...
"Emergency Alarm" - a 120 second continuous sounding with pitch alternating between 133 Hz and 400 Hz "Alarm Passed/All Clear" a 30 second continuous sounding with a constant pitch of 400 Hz, repeated twice, with 30 second pauses between the signals "Test Alarm" - a 6 second sounding ramping up to 400 Hz over the duration
Large diameter, low-pitched steam whistles were used on light houses, likely beginning in the 1850s. [2] The earliest use of steam whistles was as boiler low-water alarms [3] in the 18th century [4] and early 19th century. [5] During the 1830s, whistles were adopted by railroads [6] and steamship companies. [7]
When a sentry meerkat senses danger, they apprise their companions by letting out a high-pitched call or squeal. ... If the sentry sees a predator, it raises the alarm, and all the exposed ...
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 ...