Mechanics and material
Unlike other whistles, they are placed inside the mouth and the pitch is controlled by placement of the tongue behind the whistle. They are commonly made of plastic, aluminum, stainless steel, silver, brass, titanium, corion, jade, buffalo horn and other materials. Shepherd's whistles are designed to communicate clearly and at distances up to several hundred yards the commands of the owner to his working dog. They produce clear, high-frequency tones of an easily-modulated and variable pitch, allowing the shepherd to communicate a variety of commands. The pitch is designed to be at the optimal frequency for the border collie's hearing, and for penetration and distance to cut through adverse weather when gathering sheep.