Tin whistle
In recent years a number of instrument builders have started lines of "high-end," hand-made whistles, which can cost hundreds of dollars US each — expensive in comparison to cheap whistles, but nevertheless cheaper than most other instruments. These companies are typically either a single individual or a very small group of craftsmen who work closely together. The instruments are distinguished from the inexpensive whistles in that each whistle is individually manufactured and "voiced" by a skilled person rather than made in a factory.
Physics of whistles
Whistles that generate sound through fluctuations of momentum or a force exerted on the surrounding medium are called dipole-like sources. The figure on the right is example of a small "rigid" sphere that is moving back and forth in a given direction. If the sphere is small with respect to the wavelength of the sound emitted, it can be called a point dipole. A force must be applied to the sphere in a specific direction to move it. The surrounding medium in the direction of motion is compressed to radiate sound, but the medium at right angles slides past the sphere and is not compressed.