Research has proven that dogs react well to commands if delivered through high frequency whistles. But imagine a scene where one unfortunate day your dog runs away on a busy street, you want to call him back but panic chokes you or the noise doesn't ket your voice reach him!.High Frequency whistle for Dogs is a metal dog whistle that lets you communicate to your dog despite the noise around you and its tone stays same. Its adjustable to a constant frequency for unambiguous commands. Features: Metal and plastic body, with frequency guard, guarantees a uniform tone frequency, Individually tunable, Very quite.