A whistle is a small device that produces a high-pitched sound when air is forced through it. It is commonly used as a signal to grab attention or convey messages over long distances. Whistles can be made from various materials, including metal, plastic, or wood, and come in different shapes and sizes. In many contexts, such as sports or emergency situations, a whistle serves as a crucial communication tool. For example, a referee uses a whistle to signal the start or stop of a game, while a lifeguard may use one to alert swimmers of danger.