Falling Whistles
Falling Whistles sells whistles for $34 to $104 to raise money for education, advocacy, and the rehabilitation of war-affected people in Congo. The organization got its name from a journal written by its founder, sharing his experiences during a trip to eastern Congo in 2008. During that trip, Falling Whistles' founder met a group of five former child soldiers who told him that some children who were too young to carry weapons were sent into battle armed only with whistles. By wearing whistles, the campaign aims to use this weapon as a tool of protest and to raise awareness of the situation in Congo. As of September 2010, $500,000 has been raised.
Physics of whistles
A pea whistle is constructionally identical to a 'police whistle' but the chamber contains a small ball, known as the pea but usually a material such as plastic or hard rubber. When blown the pea moves chaotically in the chamber, interrupting and modulating the airflow to create a typical warbling/shrieking effect. Such whistles are traditionally used by association football referees and those of other games.