Sir Francis Galton invented the dog whistle in 1876 to test the limits of animal hearing.

Sir Francis Galton, a renowned Victorian polymath and cousin of Charles Darwin, developed the 'Galton Whistle' in 1876. His primary goal was to explore the range of hearing across different species, a field known as psychoacoustics. The original device was a small brass tube with a screw-plug that allowed him to change the length of the pipe and vary the pitch.During his experiments, Galton observed that as the pitch increased, it eventually became inaudible to human ears while remaining clearly audible to animals. He famously walked through the streets of London and visited the London Zoological Gardens to test his invention on various creatures. He noted that small dogs were particularly sensitive to these high-frequency ultrasonic waves.Modern research confirms Galton's early findings regarding the hearing ranges of mammals. While the average human hearing range is 20 Hz to 20,000 Hz, dogs can detect frequencies between 67 Hz and 45,000 Hz. Cats possess even more acute hearing, reaching up to 64,000 Hz, which helps them locate the high-pitched squeaks of rodents.Galton's work laid the foundation for the development of modern ultrasonic technology. Today, these whistles are used for training because they produce a sound that carries long distances without disturbing people. The 'silent' nature of the whistle is simply a result of the sound waves vibrating faster than the human eardrum can physically respond.