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
The title above is used since it is commonly used to describe whistles similar to those used by police in America and elsewhere. There are a number of whistles that operate in the same manner as the police whistle and there are number of whistles that are used by police elsewhere that do not operate in the same manner as the police whistle. The London Metropolitan police use a linear whistle, more like a small recorder. Police whistles are commonly used by referees and umpires in sporting events.