Shepherd's whistle

[3] Shepherd's whistles are used to communicate clearly, and at distances up to 2 miles (3.2 km), the commands of the owner to their 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 at an optimal frequency for the herding dog's hearing, and for penetration and distance to cut through adverse weather when gathering sheep.

[8] They are commonly made of plastic, aluminum, stainless steel, silver, brass, titanium, Corian, jade, buffalo horn and other materials.

[9] The material affects the properties of the whistle, including the loudness, timbre, and range in pitch.

The whistle's shape is best described as a flat circle of material, folded in half on a center line.

The design can also be varied to make the faces squarish, rectangular, or even a triangular A-shape, and handles or a hole for suspending the whistle as a pendant can be added.

The lower hole opens onto an otherwise closed pocket of air, in the space between the whistle and the bottom of the mouth.