Dog Whistle

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.