A dog whistle (also known as silent whistle or Galton's whistle) is a type of whistle used in the training of dogs and cats. It was invented by Francis Galton. This is discussed quite briefly in his book Inquiries into Human Faculty and its Development (Galton 1883:27). In his discussion (Galton 1883:26-27) of his experiments to test the range of frequencies that could be heard by various animals including humans, he notes that cats had the most sensitive hearing, being able to hear notes too shrill for humans to hear from a considerable distance, and small dogs can also hear these notes, while large dogs cannot.
The frequency range of a dog whistle is largely out of the range of human hearing. Typically, a dog whistle is within the range of 16000 Hz to 22000 Hz with only the frequencies below 20000 Hz audible to the human ear. Some dog whistles have adjustable sliders for active control of the frequency produced.
Depending on the way the whistle is used, a trainer may simply ga