It’s well known that many animals are particularly sensitive to high-frequency sounds that humans can’t hear. Many commercial pest repellers based on this principle are available, most of them ...

For years ultrasonics meant something only to dogs and other subhuman creatures. One of the few uses of ultra-high sound waves was in whistles, too high-pitched for human ears, to call pets. Today ...

"My son, Billy, picked up this silent dog whistle at a pet supply store." My friend George held out his hand to show me a small shiny metal whistle and then he continued, "Billy said that he was told ...

In the summer of 1876, in a workshop on the outskirts of London, Francis Galton was busy fashioning brass tubing into an ultrasonic whistle. This unique sliding whistle would produce high-pitched ...