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A dog whistle (also known as silent whistle or Galton's whistle) is a type of whistle that emits sound in the ultrasonic range, which people cannot hear but dogs and cats can. It is used in the training of dogs and cats. It was invented in 1876 by Francis Galton. The whistle was mentioned in his book Inquiries into Human Faculty and its Development in which he describes experiments to test the range of frequencies that could be heard by various animals,
The range of human hearing is typically considered to be between 20 Hz and 20 kHz. The top end of a dog's hearing range is about 45 kHz, while a cat's is 64 kHz. It is thought that the wild ancestors of cats and dogs evolved this higher hearing range in order to hear high frequency sounds made by their preferred prey, small rodents. The frequency of most dog whistles is within the range of 23 to 54 kHz, so they are above the range of human hearing, although some are adjustable down into the human range. To human ears, a dog whistle makes a quiet hissing sound. The advantage of the dog whistle is that it doesn't produce the loud disturbing noise that an audible whistle would produce, so it can be used without disturbing nearby people. Some dog whistles have adjustable sliders for active control of the frequency produced. Trainers may use the whistle to simply gather a dog's attention, or to inflict pain for the purpose of behavior modification.
In addition to lung-powered whistles, the term dog whistle is also used for electronic dog training devices that emit ultrasonic sound via piezoelectric emitters. The electronic variety are sometimes coupled with bark detection circuits in an effort to curb barking behavior.
These kind of whistles are also used to determine the hearing range of people or for physics demonstrations.
Dog-whistle politics is political messaging employing coded language that appears to mean one thing to the general population but has an additional, different or more specific resonance for a targeted subgroup. The phrase is only ever used as a pejorative, because of the inherently deceptive nature of the practice and because the dog-whistle messages are frequently themselves distasteful, for example by empathizing with racist attitudes. It is an analogy to dog whistles, which are built in such a way that their high-frequency whistle is heard by dogs, but is inaudible to humans.
A whistle or call is a simple aerophone, an instrument which produces sound from a stream of forced air. It may be mouth-operated, or powered by air pressure, steam, or other means. Whistles vary in size from a small slide whistle or nose flute type to a large multi-piped church organ.
The whistle has its roots dating back to ancient China, where night watchmen would blow into the tops of acorns to alert the towns to invading Mongolians, in the third century. In ancient Egypt two blades of the papyrus plant along the Nile river were held together in between the palms. By blowing into the palms the papyrus leaves would make a loud vibrant sound.
Other whistles (cat whistle, bird whistle, bird call, mosquito repellent) include bird calls, game calls, shepherd's whistles, Swiss warblers, Chinese pigeon whistles, Chinese and Japanese kite whistles, cuckoo clocks whistles, communication tube whistles, whistling kettles, whistling tops and various toy whistles.
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