whistle

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whistle

1. a device for making a shrill high-pitched sound by means of air or steam under pressure
2. Music any pipe that is blown down its end and produces sounds on the principle of a flue pipe, usually having as a mouthpiece a fipple cut in the side

Whistle

 

a generator that converts the energy of a fluid stream into the energy of acoustic vibrations. Unlike a siren, a whistle has no moving parts and is therefore simpler to manufacture and use. Depending on the working fluid for which they are designed, whistles are classified as gas-jet or jet liquid. Gas-jet whistles in turn are subdivided into low- and high-pressure types. As a rule, low-pressure whistles have a relatively high efficiency but generate little power, and until recently they were used only for signaling. However, with methods for increasing power output, uses have now been found for whistles in industry, for example, in the coagulation of aerosols and in the acceleration of processes of heat and mass transfer.

The simplest low-pressure whistle is the familiar lip whistle, which consists of a slotted inlet and a resonance chamber, usually cylindrical in shape. Air fed into the inlet is split into two streams by the sharp edge of the resonator. One stream exits into the surrounding medium, while the other enters the resonance chamber, thereby increasing the pressure. After a period of time that depends on the size of the chamber, the second stream interrupts the main flow, as a result of which there is a periodic compression and rarefaction of the air that is propagated as acoustic waves. Lip whistles ordinarily operate at air pressures not exceeding 1.4 atmospheres and generate acoustic power of the order of 1 watt. Some designs enable several kilowatts of power to be generated.

The ultrasonic Galton whistle and vortex whistles are further examples of low-pressure devices. Vortex whistles have a cylindrical chamber into which a gas or liquid is introduced tangentially. A narrow tube extends along the axis of the chamber, and it is through this tube that the gas exits, radiating sound energy. Elastic vibrations are induced by a combination of the pressure decrease along the whistle axis that results from vortex motion and the periodic pressure equalization that results from the rush of gas from the atmosphere into the tube’s outlet. At frequencies up to 30 kilohertz, the power output of a vortex whistle is usually of the order of several watts. A representative high-pressure whistle is the Hartmann generator, which has a maximum power output of 0.5 kilowatt.

The design and operating principles of jet liquid whistles are analogous to those of the gas-jet type. The most common are lamellar jet liquid whistles, which function by using a liquid stream under high pressure to excite resonant vibrations of the vibrator—a blade or rod.

REFERENCES

Shkol’nikova, P. Sh. “Vozdukhostruinye generatory akusticheskikh kolebanii dlia koaguliatsii aerozolei.” Akusticheskii zhurnal, 1963, vol. 9, no. 3, pp. 368–75.
Bergmann, L. Ul’trazvuk i ego primenenie v nauke i tekhnike, 2nd ed. Moscow, 1957. (Translated from German.)

IU. IA. BORISOV

References in periodicals archive ?
Near and Miceli (1996) suggest that the decision to blow the whistle is affected by the personality Waits of the individual, and the environment surrounding the individual.
The survey showed that people mostly blow the whistle because they are absolutely angry over something that they feel is unfair or unjust," said Vadera.
There will be a positive relationship between perceptions of intention about organizational wrongdoing and decisions to blow the whistle.
Public Concern at Work, the charity which helps people raise concerns, said workers were twice as likely to blow the whistle on wrongdoings than they were five years ago.
At the sad of the grass drill, Lombardi would blow the whistle and we'd run around the goal posts and, back to the far end of the field, probably 250 yards, and sprinting all the way.
NAIRN COUNTY were keen to blow the whistle on bad refereeing after crashing out of the Highland League Cup to Keith.
Soon, the trainer need only blow the whistle to get the animal's cooperation for a dental exam.
Most people find it difficult to blow the whistle, even when troubled IS projects clearly need to be turned around.
In particular, they should do everything they can to encourage organizational controls that expose corruption early--and stop it well before auditors have to decide whether to blow the whistle.
Stewart and Feder have proposed an alternative job description: They want to set up an office that would help scientists who blow the whistle on fraud or misconduct.
It was easier to blow the whistle than to continue to lie.