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.
Physics of whistles
These devices are whistles that do not radiate sound, but are still aerodynamic whistles.
The upper figure on the right shows the basic arrangement of one version of the device. The circle on the left is the fluid source (air or liquid). A jet is formed that either goes into the upper or lower channel.