VI. Match the words in the right and left columns to make up a word expression from the text:

1. seismic a) design

2. commercial b) engineering

3. basic c) vibrations

4. circuit d) marketplace

5. electrical e) skill

6. revolutionary f) signals

7. sensory g) changes

Sonar

Sonar is an acronym¹ for Sound Navigation and Ranging². It is divided into two categories, active and passive. In active sonar, sound pulses between 2 kHz and 40 kHz are transmitted into the water, and the resulting echoes are detected and analyzed. Uses of active sonar include: detection and localization of undersea bodies, navigation, communication, and mapping the sea floor. A maximum operating range² of 10 to 100 kilometers is typical. In comparison, passive sonar simply listens to underwater sounds, which includes: natural turbulence, marine life, and mechanical sounds from submarines and surface vessels. Since passive sonar emits no energy, it is ideal for covert³ operations. The most important application of passive sonar is in military surveillance systems⁴ that detect and track⁵ submarines. Passive sonar typically uses lower frequencies than active sonar because they propagate⁶ through the water with less absorption. Detection ranges² can be thousands of kilometers.

Digital Signal Processing has revolutionized sonar in many of the same areas: pulse generation, pulse compression, and filtering of detected signals. On the one hand, sonar is simpler than radar because of the lower frequencies. On the other hand, sonar is more difficult than radar because the environment is much less uniform and stable. Sonar systems usually use many ways of transmitting and receiving elements, rather than just a single channel. By properly controlling and mixing the signals in these many elements, the sonar system can steer⁷ the emitted pulse to the desired location and determine the direction that echoes are received from. To handle these multiple channels, sonar systems require the same massive Digital Signal Processing computing power. (1497 p.s.)

Vocabulary

1. an acronym – аббревиатура, сокращение

2. Ranging – определение расстояния

operating range – диапазон действия

ranges – дальность, диапазон

3. covert – секретный

4. surveillance systems – разведывательные системы

5. to track – следить, преследовать

6. to propagate – распространяться

7. to steer – направлять

I. Answer the question:

What is the main application of passive sonar?

1. Detection and tracking of herds of fish.

2. Localization of dead civilizations.

3. Military tracking systems for binding submarines.

4. Location of underwater volcanoes.

II. Decide which statement matches the text:

1. A minimum operating range of 10 to 100 kilometres is typical of active sonar.

2. Low frequency sound pulses spread through the water with great absorption.

3. Sonar can only be used in unchangeable environments.

4. Passive sonar emits no radiation.

III. Decide which statement does not match the text:

1. Active sonar transmits sound waves into the water and listens to the echoes.

2. Passive sonar merely analyzes undersea sounds.

3. Detection ranges of passive sonar are very limited.

4. DSP has not had any influence on sonar.

IV. Decide which definitions match the following terms:

1. surveillance systems a) distance at which a system words

2. operating range b) military organization for collecting and

processing information

3. sonar c) sonic waves of different frequencies

4. sound pulses d) sound detection and tracking of various undersea

objects

V. Fill in the gaps with the words from the list below:

to track, operating range, covert, to steer, surveillance systems

1. ____________________ of the new generation missile is 150-200 kilometres.

2. Computer crime is so common these days that it is hard ____________________ the culprit sometimes.

3. The whole team have worked undercover; no one has had the slightest idea of their ____________________ mission.

4. ____________________ of this bind are extremely sophisticated and very expensive at present.

5. Usually built-in electronic equipment guides big ships in the ocean, but one needs a basic skill and a firm hand ____________________ to steer a smaller vessel.