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.
Vocal register
The whistle register is the highest register of the human voice. The whistle register is so called because the timbre of the notes that are produced from this register are similar to that of a whistle or the upper notes of a flute, whereas the modal register tends to have a warmer, less shrill timbre. Women of all voice types can use the whistle register. With proper vocal training, it is possible for most women and some men to develop this part of the voice. Children can also phonate in the whistle register, without conscious effort.