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A whistle (or call) is a simple aerophone, an instrument which produces sound from a stream of forced 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.
The whistle has its roots dating back to ancient China, where night watchmen would blow into the tops of acorns to alert the towns to invading Mongolians, in the third century. In ancient Egypt two blades of the papyrus plant along the Nile river were held together in between the palms. By blowing into the palms the papyrus leaves would make a loud vibrant sound.
Types of whistle 
Many types exist, small mouth blown whistles for various functions from toys to hunting using bird and fowl calls type whistles, to professional whistles as police, boatswain's pipe, military, sports whistles (also called pea whistles), to much larger steam or air preasure operated ones as train whistles, which are steam whistles specifically designed for use on locomotives and ships. Although almost all whistles have some musical character, common whistles are not usually considered musical instruments, since they cannot play a melody, unless used as a – very shrill and loud – noise and rhythm instrument. However, musical whistles exist, including various 2-octave musical instruments known as tin whistles (sometimes called pennywhistles or low whistles), as well as the calliope (an array of separately actuable steam whistles), organ pipes and the recorder. Pea whistles are used in jazz and Latin music for rhythm, much as a percussion instrument is; children often use them as a toy music instrument. There is also a more diverse type of whistle used for giving commands to sheepdogs at work, which can emit almost any tone the shepherd wishes, in order to signal different commands. This whistle is known as a shepherd's whistle.
How it works 
The mouthpiece of a whistle is shaped to create a narrow windway. Thunder type whistles use a shaped mouthpiece whilst police and samba type whistles use a form of fipple to constrict the flow (see illustrations). The thin flow of air is directed against a narrow blade, called a labium (Latin: lip) or windcutter. The air stream does not simply split in two, but is unstable and oscillates rapidly back and forth between the two sides of the blade, creating a string of pressure pulses that radiate as sound waves. By attaching a resonant chamber to the basic whistle, it may be tuned to a particular note and made louder. The oscillating airflow excites standing waves in the resonance chamber which in turn stabilise the frequency of oscillation. For flute type whistles (police and samba) the length of the chamber determines the resonant frequency (pitch) of the whistle. Thunderer type whistles are more akin to ocarinas and need to be modelled by a Helmholtz resonator. The resonance chamber may also contain a small light ball, usually called the pea, which rattles around inside, creating a distinctive chaotic vibrato sound. Japanese bird whistles use several small balls and are half filled with water in order to reproduce the sound of a bird song.
A steam whistle works the same way, but using steam as a source of pressure: such whistles can produce extremely high sound intensities.
Sometimes, air or wind blowing past an opening can create an unintentional "whistle" effect. A common one is the opened sunroof of a car: air passing over the top of the vehicle can, at certain speeds, strike the back edge of the sunroof, creating a very low frequency whistle which is resonated by the closed interior of the car. Since the sound frequency is infrasonic, around 4 Hz, the effect is very uncomfortable for occupants, who feel the vibration rather than hear it. Such low frequencies can induce nausea, headache, disorientation and dizziness. The effect can be prevented by opening a side window a few inches. Subsonic whistles have also been developed for use as non-lethal area-denial weapons for crowd control purposes, or to deliberately create a sense of uneasiness in an enemy.
Fields and usages 
Police whistles 
In England since the Metropolitan Police Services inception in 1829, officers have been issued a whistle. Prior to this, police used hand rattles, with whistles only being used as musical instruments or toys. Both 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 Forces in Great Britain.
J Stevens & Son & J Dixon & sons made police whistles from around the 1840s, T Yates made Beaufort whistles for the Liverpool Police in the 1870s. The 1880s and 1890s saw police whistles made by W Dowler & Sons, J Hudson & Co, J Barrall, R A Walton, H A Ward and A De Courcy & Co.
Police whistles fell into disuse in many countries[examples needed] in 1969, when early hand-held radios were brought into service. With the rise of the motor car, the whistle was no longer usefully audible in urban areas. The whistle is still used by some police forces today[examples needed], and engraved ceremonial versions are sometimes presented to police officers upon occasions such as their retirement.
Industrial whistles 
Industrial whistles are used for signalling and timekeeping both on railroad and ships, and in factories. Most of these whistles were steam powered and not standardized. Individual locomotives could be identified by their whistles. At noontime in industrial areas up into the 1950s whistles of every pitch could be heard, as each factory had a boiler and a whistle, if not full steam power.
Ships' whistles must be very loud for safety on the seas. Modern ships' whistles can be electrically or steam driven. RMS Queen Mary was originally equipped with three electric Tyfon whistles in 1935. They could be heard at least ten miles away and were tuned to 55 Hz, a low bass A note that was chosen for maximum passenger comfort despite the high sound pressure level. One of the three whistles was taken back to Kockum Sonics in Malmö, Sweden, where it was refurbished for a new life of service aboard the RMS Queen Mary 2. Modern IMO regulations specify ships' whistle frequencies to be in the range 70–200 Hz for vessels that are over 200 metres in length. Traditionally, the lower the frequency, the larger the ship. The Queen Mary 2, being 345 metres long, was given the lowest possible frequency (70 Hz) for her regulation whistles which means she carries both 70 Hz modern whistles and a single vintage 55 Hz whistle.
Railroads in particular used elaborate whistle codes for communication both within the train and with other trains. These methods are maintained today with motor-powered air horns. Trucks also use air horns, especially since they often have air brakes and so there is already a source of compressed air on board.
Train guards (US: Conductors) and station staff use whistles to attract attention. The actual command or message is passed on by flag, hand signal or paddle.
Whistles are used by referees to officiate at sporting matches. The whistle was first used to stop a sports match by William Atack in a game of rugby in New Zealand in 1884. Before that game, all referees simply used their voices to control the flow of play.
Some sports use different types of whistles, but one used around the world in many sports is the Fox 40 whistle. The Fox 40 whistle is a pealess whistle which creates sound using air pressure only. This whistle is used at basketball, field hockey, ice hockey, American football, soccer football, water polo, and numerous other games, since it can be readily heard over the noise of the spectators and players.
Another whistle that is widely used for games such as touch football, rugby league and rugby union is called the "Thunderer 58.5", and it is made by the Acme Whistles company. This is a metal whistle containing a pea made out of cork. This one is primarily used because it makes a deep, low-pitched shrill that can sometimes be heard from hundreds of metres away.
A samba whistle with three tones
The whistle is used by a leader in samba percussion groups to help catch the percussionists' attention. The traditional samba whistle has three tones, but as the size of the percussion section rose, pealess whistles became more popular due to their high pitch and their loud sound.
The slide whistle (or swanee whistle) was a common instrument in some types of music, including being used at times in early Jazz, and was popular as a musical effect in the early days of radio and television.
The tin whistle (or penny whistle) is a 6 holed instruments with two octave range that is also used to make music.
Pitch pipes are reed whistles used to help in tuning musical instruments and have been common since the 1850s.
During the 1990s, it was common for whistles to be employed by the audiences at raves, allowing a level of interaction between the partygoer and the DJ. In fact, there were a series of raves during the late 1990s named "Whistle". Held at a nightclub named Shampoo in Philadelphia, the Whistle parties (raves) were held once annually, making each party a sequel to the one the year before.
Whistles were used in various military engagements in the 20th century. They were used primarily to initiate a pre-set plan so that all parts (within earshot) would move simultaneously. For example, officers in the first world war would sometimes blow whistles to signal all troops along a broad stretch of trench to attack at the same time.
In the Canadian Navy, the so-called Bosn' whistle or Boatswain's call is still in use for ceremonial purpose on board RCN ships. It was used in the past to command order like carry on, soup time or colors ceremony.
Game calls 
Hunters and wildlife photographers often use specialised whistles as game callers. Fox whistles mimic the sound of a distressed rabbit, causing the fox to run towards the caller. There are two main types of fox whistle: the button type or a simple folded piece of metal known as the Tenterfield whistle, named after the town in Australia where they originated.
Similar callers exist for crows or wild dogs.
Other whistles include bird calls, game calls, shepherd's whistles, Swiss warblers, Chinese pigeon whistles, Chinese and Japanese kite whistles, cuckoo clocks whistles, communication tube whistles, whistling kettles, whistling tops and various toy whistles.
Patents and inventors 
In 1868 Joseph Hudson of Birmingham, England, made the first whistle ever to be used by a football referee. New Zealand referee William Atack was the world's first to use a whistle to stop a game of sport in 1884. It was used for the first time (allegedly) at a game held at Nottingham Forest, prior to this referees used handkerchiefs to attract players' attention.
By 1884, Joseph Hudson had perfected his whistles and he released the world's most successful whistle to date, the "Acme Thunderer" (the first ever pea whistle). The whistle has been used as an alarm or attention-getting instrument by all manner of industries, sports and revellers. It continues to sell in great quantities throughout the world.
See also 
- Taylor, J. "The Victorian Police Rattle Mystery" The Constabulary (2003)
- The Voice of the Queen Mary
- Kockum Sonics: Tyfon product IMO regulations
- Berrett, Joshua (2004). Louis Armstrong & Paul Whiteman: Two Kings of Jazz, p. 62. Yale University Press. ISBN 0-300-10384-0.
- Louis Armstrong's discography: Early years - 1901 1925
||This article's use of external links may not follow Wikipedia's policies or guidelines. (March 2011)|
- The Botswain's Call handbook The Marine Society & Sea Cadets
- Whistle museum
- Clay Whistles
- The dictionary definition of whistle at Wiktionary
- Chisholm, Hugh, ed. (1911). "whistle". Encyclopædia Britannica (11th ed.). Cambridge University Press.
- Police or Fire Whistles
- World War I American Police whistles discussed in federal court
- American Whistle Manufacturers by Avner Strauss