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An aerodynamic whistle (or call) is a simple aerophone, an instrument which produces sound from a stream of gas, most commonly air. It may be mouth-operated, or powered by air pressure, steam, or other means. Whistles vary in size from a small slide whistle or nose flute type to a large multi-piped church organ. Whistles have been around since early humans first carved out a gourd or branch and found they could make sound with it. In prehistoric Egypt, small shells were used as whistles. Many present day wind instruments are inheritors of these early whistles. With the rise of more mechanical power, other forms of whistles have been developed. One characteristic of a whistle is that it creates a pure, or nearly pure, tone. There are many ways to create pure tones, but we restrict the descriptions here to what are called aerodynamic whistles. Strictly speaking, they are fluid mechanical whistles since they occur in gases, such as air or steam, as well as in liquids, such as water. The only difference between them is the fluid density and the sound speed. The word aerodynamic whistle is used here since it is in common use. The conversion of flow energy to sound comes from an interaction between a solid material and a fluid stream. The forces in some whistles are sufficient to set the solid material in motion. Classic examples are Aeolian tones that result in galloping power lines,〔Conductor gallop,〕 or the Tacoma Narrows Bridge (galloping Gertie).〔Tacoma Narrows Bridge (1940)〕 Other examples are circular disks set into vibration. The whistles described in this article are in a subclass where only the fluid is in motion and there is no significant dependent motion of the interacting solid. Depending on the geometry there are two basic types of whistles, those that generate sound though oscillations of fluid mass flow and those that generate sound through oscillations of the force applied to the surrounding medium. ==Early police whistles== Joseph Hudson set up J Hudson & Co in Birmingham, UK in 1870. With his younger brother James, he designed the 'Acme City' brass whistle. This became the first referee whistle used at association football matches during the 1878–79 Football Association Cup match between Nottingham Forest and Sheffield. Prior to the introduction of the whistle, handkerchiefs were used by the umpires to signal to the players. In 1883 he began experimenting with pea-whistle designs that could produce an intense sound that could grab attention from over a mile away. His invention was discovered by accident, when he accidentally dropped his violin and it shattered on the floor. Observing how the discordant sound of the breaking strings travelled (trill effect), Hudson had the idea to put a pea in the whistle.〔(History of the Whistle )〕 Prior to this, whistles were much quieter, and were only thought of as musical instruments or toys for children. After observing the problems that local police were having with effectively communicating with rattles,〔Taylor, J. ("The Victorian Police Rattle Mystery" ) ''The Constabulary'' (2003)〕 he realised that his whistle designs could be used as an effective aid to their work.〔(ACME Whistles )〕 Hudson demonstrated his whistle to Scotland Yard and was awarded his first contract in 1884. Both Ratchet rattles and whistles were used to call for back-up in areas where neighborhood beats overlapped, and following their success in London, the whistle was adopted by most police in the United Kingdom. This police whistle monopoly gradually made Hudson the largest whistle manufacturer in the world, supplying police forces and other general services everywhere. His whistle is still used by many forces worldwide. His design, was improved as the 'Acme Thunderer', the first ever pea whistle, which remains the most used whistle in the world; for train guards, dog handlers and police officers.From the 1880s and 90s, J. Hudson & Co began facing greater competition, as other whistle manufacturing companies were established, including W. Dowler & Sons, J. Barrall, R. A. Walton, H. A. Ward and A. De Courcy & Co. In 1987, Ron Foxcroft released the Fox 40 pealess whistle, designed to replace the pea whistle and be more reliable. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Whistle」の詳細全文を読む スポンサード リンク
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