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 classic literature ?
He placed a finger in his mouth, and drew a long, shrill whistle, which was answered from the rocks that were guarded by the Mohicans.
Streaming files of wild ducks began to make their appearance high in the air; the bark of the squirrel might be heard from the groves of beech and hickory- nuts, and the pensive whistle of the quail at intervals from the neighboring stubble field.
und Heathcliff's noan t' chap to coom at MY whistle - happen he'll be less hard o' hearing wi' YE
She stopped and listened to him and somehow his cheerful, friendly little whistle gave her a pleased feeling--even a disagreeable little girl may be lonely, and the big closed house and big bare moor and big bare gardens had made this one feel as if there was no one left in the world but herself.
Scrooge's niece played well upon the harp; and played among other tunes a simple little air (a mere nothing: you might learn to whistle it in two minutes), which had been familiar to the child who fetched Scrooge from the boarding-school, as he had been reminded by the Ghost of Christmas Past.
He made up his mouth as if to whistle, but he didn't whistle.
He seemed to be waiting and listening for some one's approach, and presently the sound of a heavy step, with an accompanying whistle, was heard across the large empty entrance-hall.
Truly your golden chain hath not long abidden with me, and will now sustain, around the neck of an outlaw deer-stealer, the whistle wherewith he calleth on his hounds.
It was not yet seven, she said, by a long way; she knew her rights and she would have them; and she was still arguing with me when a little low whistle sounded a good way off upon the hill.
I have only to blow my whistle and you will be at my brother's house before nightfall.
Presently they heard some one coming up the road whistling gaily, as though he owned the whole world and 'twas but made to whistle in.
And hardly had the carriage turned the corner and rattled into the high road with this inexplicable pair, than the whistle broke forth - prolonged, and low and tremulous; and the groom, already so far relieved, vented the rest of his surprise in one simple English word, friendly to the mouth of Jack-tar and the sooty pitman, and hurried to spread the news round the servants' hall of Naseby House.