A simple whistle is a woodwind instrument which produces sound from a

stream of forced air.

Many types exist, from small police and sports whistles (also called

pea whistles), to much larger train whistles, which are steam whistles

specifically designed for use on locomotives and ships. Although

whistles have a musical characteristic (for example train whistles

sound a minor-seventh musical chord) whistles are not usually

considered "musical" in the sense of being able to play a chosen

melody, but mainly the small whistles can also be used as a – very

shrill and loud – noise and rhythm instrument. However, musical

whistles exist, including any of several 2-octave musical instruments

known as tin whistles (sometimes known as 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 as a percussion instrument, and children often use

them as a toy music instrument.

The whistle works by causing the smooth flow of air to be split by a

narrow blade, sometimes called a fipple, creating a turbulent vortex

which causes the air to vibrate. By attaching a resonant chamber to the

basic whistle, it may be tuned to a particular note and made louder.

The length of the chamber typically defines the resonance frequency. A

whistle may also contain a small light ball, usually called the pea,

which rattles around inside, creating a chaotic vibrato effect that

intensifies the 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, unintentional whistles can be set up. 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 weapons, or to deliberately create a sense of uneasiness in

an enemy.[citation needed]

Contents [hide]
1 History
2 Police whistles
3 Industrial whistles
4 Safety
5 Sporting
6 References
7 External links

History
The whistle has its roots dating back to ancient China. Chinese night

watchmen used to blow into the tops of acorns in order to alert the

towns of invading Mongolians.[citation needed]

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.

In 1868 Joseph Hudson (inventor) 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.

Police whistles
Hudson later made the first police whistle for the Metropolitan Police

Service. 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 neighbourhood beats

overlapped, and following their success in London, the whistle was

adopted by most counties in England.

Police whistles fell largely into disuse in 1959, 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, and engraved ceremonial

versions are sometimes presented to police officers upon occasions such

as their retirement.

Industrial whistles

Examples of police whistlesIndustrial 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.

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 whistles generally produce three or four different frequencies at

the same time, to produce a non-major chord, that is distinct, loud,

and low in pitch.

Ship's whistles must be very loud for safety on the seas. Modern ship's

whistles can be electrically driven or steam driven. RMS Queen Mary was

originally equipped with three electric Tyfon whistles in 1932. 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.[1] 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 meters in length.[2] Traditionally, the lower

the frequency, the larger the ship. The Queen Mary 2, being 345 meters

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.

Safety
Whistles are often used as warning devices or as safety devices serving

to attract attention to the user. Some cyclists use a whistle as a

substitute for a bell or horn. It should be noted, however, that many

jurisdictions require that the warning device be permanently attached

to the bicycle.

Rescue or Survival whistles are often packed in survival kits and

attached to Personal flotation devices to allow a victim to signal for

help. The whistle is audible at much greater distances than the human

voice, and is less likely to cause exhaustion if used repeatedly.

Survival whistles differ from pea whistles in that they are usually

flat, so that water cannot collect inside if the user is immersed, for

example after falling overboard from a boat.

Whistles can also produce sounds at pitches inaudible to the human ear

such as dog whistles which can be heard by dogs at a range beyond that

of human sensory perception, or at least conscious perception.

Sporting
Whistles are used by referees to officiate sporting matches. Some

sports use different types of whistles, but one used around the world

in many sports is the Fox 40, a pealess whistle which creates sound

using air pressure only.

The Fox 40 is used in Basketball, Hockey, Ice Hockey, Soccer and

numerous other games, as it can be heard easily over the noise of the

audience.

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