АНОТАЦІЯ

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The noise problem created by commercial and military jet take offs, landings and ground operations at airports near residential areas has become a very serious problem within the last years. The pattern of sound from a jet engine makes the noise problem even more bothersome than that coming from other types of engines. For example, the noise from a reciprocating engine rises sharply as the airplane propeller passes an observer on the ground and then drops off almost as quickly. A jet reaches a peak after the aircraft passes, and is at an angle of approximately 45º to the observer. This noise then stays at a relatively high level for a considerable length of time. The noise from a turbojet is also more annoying because it overlaps the ordinary speech frequencies more than the noise from a reciprocating engine and propeller combination. Since the noise is produced by the high-velocity exhaust gas shearing through the still air, it follows that if the exhaust velocity is slower and the mixing area wider, the exhaust noise levels can be brought down to the point where a sound suppressor is not necessary. The exhaust-gas velocity of a turbofan is slower than a turbojet of a comparable size because more energy must be removed by the turbine to drive the fan. The fan exhaust velocity is relatively low and creates less of a noise problem, noise levels are also lower in the high-bypass-ratio turbofan engine through the elimination of the inlet guide vanes and the resulting reduction of the "siren" effect. The noise generated by this effect occurs when the columns of air created by the compressor inlet guide vanes are cut by the rapidly moving compressor blades, generating high-frequency pressure fluctuations. Further noise reductions are achieved by lining the fan shroud with acoustical materials, thus, dampening the pressure fluctuations and by spacing the outlet guide vanes farther away from the compressor. For these reasons, fan engines in general do not need any sound suppressor. The function of the noise suppressor is to lower the level of sound about 25 to 30 dB, as well as to change the frequency, and to do this with a minimum sacrifice in engine thrust or additional weight. The two facets of the noise problem, ground operation and airborne operation, tend themselves to two solutions. Noise suppressors can be portable devices for use on the ground by maintenance personnel, or they can be the integral part of the aircraft engine installation. Airborne suppressors are more difficult to design than ground suppressors because of the weight limitations and the necessity of having the air exit in an axial direction to the engine.

Post-Reading

I. Divide the text into paragraphs. Give a title for each one. Choose the topic words of each part and define the main point of it in one phrase.

II. Make a graphic representation of the text. Share it with your partner and fill it in.

III. Say if the statements are true or false. Correct the false once.

1. The problem of aircraft noise has become one of the most urgent problems for the last several years.

2. The more energy is generated by the turbine to drive the fan the slower the exhaust-gas velocity of a turbofan is in comparison to a turbojet of the same size.

3. The elimination of the inlet guide vanes and the resulting reduction of the "siren" effect reduce noise levels in the high-bypass-ratio turbofan engine.

4. The noise generated by the "siren" effect occurs when the columns of air are cut by the stator blades.

5. To achieve better noise reduction the fan shroud is lined with insulator material.

IV. Give Russian equivalents:

V. Answer the questions:

1. What does the text deal with?

2. Why has the noise problem become one of the most important within the last several years?

3 What engines are less noisy and why?

4. Why does a turbofan need no sound suppressor?

5. Which of suppressors are more difficult to design and why?

Language in Use

I. Fill in the table using comparative and superlative adjectives. The 1^st line in each box may serve as an example.

II. a) Use adjectives in brackets either in a comparative or superlative form.

1. One of the _____ (significant) sources of cabin noise from commercial jet aircraft rather than the engines is the Auxiliary Power Unit.

2. The typical noise output of an APU is 113 decibels. This is about 27 decibels _____ (low) than that of a jet engine.

3. _____ (large) aircraft then entering service or in development, such as Lockheed L-1011, Douglass DC-10 and Airbus A3000 were designed with the _____ (stringent) requirements in mind.

4. The development of high-bypass turbofans that powered these _____ (new) aircraft was prompted by the need for _____ (great) thrust and fuel efficiency.

5. Not only does the fan produce _____ (little) noise per pound of thrust, but the _____ (cool) air mixing with the hot jet exhaust also insulates the engine, acting as a muffler.

6. This reduction can be directly observed at a major international airport, particularly one that also includes flights of _____ (old) turbojet-powered aircraft operated by _____ (poor) nations.

b) Think of 5 other adjectives and make up your own sentences. Do it the same way as in part a). Exchange your sentences with the partner. Check the results of your work.

III. Find pairs of a) synonyms, b) antonyms among the words. Mind there is one extra word in each part.

a)

affect

b)

IV. Use the prepositions in the oval to complete the sentences in the text. Render the text in Russian.

Though long of concern _____ neighbours _____ major airports, aircraft noise first became a major problem _____ the introduction of turbojet-powered commercial aircraft (Tupolev 104, Boeing 707, Dehavilland Comet) _____ the late 1950s. It was recognizes _____ the time that the noise levels produced _____ turbojet powered aircraft would be unacceptable to persons living _____ the take off pattern of major airports. Accordingly, much effect was devoted _____ developing jet noise suppressors, _____ some modest success. Take-off noise restrictions were imposed _____ some airport managements, and nearly all first-generation turbojet-powered transports were equipped _____ jet noise suppressors _____ a significant cost _____ weight, thrust, and fuel consumption.

The introduction _____ the turbofan engine, _____ its lower velocity, temporarily alleviated the jet noise problem but increased the high-frequency turbomachinary noise, which became a severe problem _____ landing approach as well as _____ take-off. This noise was reduced somewhat _____ choosing proper rotor and stator blade numbers and spacing and _____ using engines of the single-mixed-jet type.

V. a) Match the words with their definitions.

b) Choose any 5 words from the text "Noise Suppression Problem" and give your own explanation of them.

VI. Fill in the gaps using the words from the oval. Mind, there is one extra word! Translate the text into Russian in written.

The biggest _____ of aircraft jet engines suspected that the major _____of engine noise came from the region _____ the engine, where the high-velocity exhaust mixes with the lower velocity surrounding air. Engine designers in Europe _____ on changing the nozzle designs of engines, _____ by corrugating the outer edge of the exhaust nozzle. Rather than smooth and round, they made it warped or angled, often looking like a flower. This better mixed the high-velocity efflux with the air behind the engine. In the United States, designers used this _____ and another method involving venting the exhaust from several tubes. But both of these methods increased _____ and reduced engine performance, and the multi-tube approach also increased weight, sometimes _____.

Writing

You were asked to write an article (about 200 words) for a magazine on the main sources of the total noise level and possible solutions of this boring problem. Mind, the readers of the magazine are chiefly your age.

Speaking

Role-Play

Student A

The following phrases may be of great help.

To do it successfully use the following phrases.