Strolling along London's Zoological Gardens in 1876, Sir Francis Galton stopped in front of the lion enclosure, pulled out a whistle, and began blowing on it. No sound emitted from the device, but ...

ACME Pro Trialler 212 Dog Whistle | Amazon This whistle is a great all-rounder with a sound that is well within human hearing. It holds its frequency no matter how loud you blow, so your dog will ...

waves have a frequency higher than the upper limit for ... This explains why a dog can hear the ultrasound produced by a dog whistle, but humans cannot. In the first two of these applications ...