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
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005
The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

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

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.
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Hayley Longdin As part of her new role at Whistle PR, Ms Longdin will be responsible for overall client service as well as the direction of some of the agency's largest accounts.
With the unique whistling packaging there's no need to pierce the film on the meal either, your meal will literally whistle and let you know when it's ready,' she concludes.
"Her appointment, in this newly created role, represents an ongoing investment in building a great team at Whistle and providing a first-class service to our clients.
'After the second set, coach told us to play with the 'respect, whistle to whistle, and communication' code,' said Santiago in Filipino Sunday at Filoil Flying V Centre.
In accordance with the participatory principle, the representatives of the NGO 'The Whistle' helped include the empirical evidence on the treatment of whistle- blowers, although its proposal for disclosure of data containing classified information was not included in the Draft Law, meaning that in such cases the protection of whistle- blowers remained very limited.
On 21st December, 2016, the Federal Executive Council (FEC) introduced the new whistle-Blower policy that provides up to 5 per cent reward for whistle blowers for exposing fraud in both public and private sectors.
The poor old whistle: communicator extraordinary and one of the silver sounds of my elementary years.
Mexico City Mayor Miguel Angel Mancera announced Wednesday during a press conference his administration would provide whistles to women to enable them to alert police and bystanders to potential sexual assaults and street harassment. Mancera said the whistle would serve as "a warning sign to society that something is happening there, that we cannot be indifferent." He said police would be directed to respond to the sound of a whistle.