Shepherd's whistle
They are also produced commercially. Simple whistles may cost less than 1 USD in bulk; expensive ones may be quite ornate. They are commonly made of plastic, aluminum, stainless steel, silver, brass, titanium, Corian, jade, buffalo horn and other materials.
Whistle
Whistles were used by the Ancient Greeks to keep the stroke of galley slaves. The English used whistles during the Crusades to signal orders to archers. Boatswain pipes were also used in the age of sail aboard naval vessels to issue commands and salute dignitaries.