Text 3. Sound as a longitudinal wave

Key terms: sound, vibrating object, source of sound, audible region, infrasonic, infrasound, ultrasonic, ultrasound, intensity of the sound, bel, decibel

How does sound travel through air? To answer this question we must first examine the source of sound. The source of every sound is a vibrating object. The sound of the human voice begins as vibrations in the vocal cord, in the larynx. The sound from a guitar is produced only while a string vibrates. A trombone sounds only while the player’s lips vibrate. Sound is transmitted through a material medium as a longitudinal wave.

There is the definition of sound as that form of energy which can be detected by the human ear. This definition is restrictive since many animals sense frequencies that we cannot hear. We will instead consider sound as energy that travels as longitudinal waves containing regions of high and low pressure. The audible region of the sound spectrum for human beings extends from about 16 Hz at the low-frequency end to about 20 kHz at the high-frequency end. Because 20,000 Hz is the upper limit of the audible range for humans, a frequency of 25,000 Hz would sound silent to the human ear. To humans, this sound has a loudness of zero even though its intensity might be 100 dB.

Frequencies below 16 Hz are called infrasonic. If we could hear infrasound, we would hear the waves on a lake before they break against the shore. We would hear the vibrations of a pendulum, and the vibrations of the wings of a bee. Recent studies suggest that many birds and animals can detect these frequencies. Birds, many kilometres inland, may hear a lake and thus know where it is. There are so many facts about the animals being disturbed before earthquakes that scientists are considering the possibility that earthquakes produce low-fre- quency infrasound before the main shock waves begin. Possibly these waves alert the animals.

Frequencies higher than 20,000 Hz are known as ultrasonic. There are many applications of ultrasound. It is used by jewellers to clean jewellery and can be used to find internal flaws in castings. Doctors use ultrasound to break up gallstones. Because ultrasound is reflected at the boundary between different types of tissue, it can be used to form internal images of the body that are in many ways more useful than those from X-rays. It is also used in therapy to accelerate the healing of damaged tissues such as muscles.

Ultrasound is used extensively by several animals. Bats locate objects in the dark by emitting ultrasonic squeaks and then listening for the returning echoes. Dolphins use ultrasound for navigation and communication.

The intensity of the sound is the amount of sound energy passing each second through a unit area. If one joule of sound energy per second passes through an area of one square metre, then the intensity is one joule per second per square metre, or one watt per square metre. Our ears are so sensitive that an intensity of one watt per square metre is too large a sound level for us to cope with. To accommodate smaller values, a unit called the bell (B), named in honour of Alexander Graham Bell, has been defined. One bell is equal to ten picowatts per square metre (1 B = 10 pW / m2). Remember that pico is the SI prefix meaning 10'12. A smaller unit, the decibel (dB) is also used (1 B = 0.1 B).

Sound intensity depends on several factors. First, it depends on the strength of the source of sound. Second, it depends on how far away the listener is from that source. And third, it depends on the ability of the medium between the listener and the source to transmit sound energy.

LEXICAL EXERCISES

I. Pronounce these international words after the teacher and translate them:

guitar, produce, trombone, vibrate, transmit, detect, human, limit, ultrasound, reflect, therapy, accelerate, accommodated, muscle, extensive, locate, object, echo ['i:kou], dolphin, navigation, communicate, vocal, factor

II. Translate these word combination into Ukrainian:

vibrating object, vocal cord, human voice, a material medium, high (low) pressure, audible region, sound spectrum, high (low) frequency, upper limit, audible range, internal image, X-ray, ultrasonic squeak, returning echo, intensity of the sound, amount of sound energy, to pass through the unit area, one joule per second, a sound level, to cope with, in honour of, several factors, shock waves.

III. Define, to what part of speech belong the derivatives of these words and translate them:

restrict - restriction — restrictive - restricted

sense - sensitive - sensible - sensitively - sensitivity

loud — loudly - loudness — loudless

jewel — jeweller - jewelleryextend - extensive — extensively - extension - extended

human - humane - humanity - humanitarian - humanism

sound - soundless - sounded - sounding

intense - intensely - intensive - intensify ~ intensity

local - localize - locate — location - localized

limit - limitless - limited - unlimited - limiting

IV. Answer these questions on the text:

1. What is the source of every sound? 2. How is sound produced by a man (guitar, trombone)? 3. What is sound? 4. What is the range of the audible region? 5. How is ultrasound used a) in medicine; b) by animals? 5. What is the intensity of the sound? 6. Give the definition of one bell. 7. What factors does sound intensity depend on? 8. What is the audible range of the average human ear? 9. What frequencies are associated with a) infrasound; b) ultrasound? 10. What is the difference between sound intensity and loudness? 11. What are the base units for sound intensity? 12. What is the difference between infrasound and ultrasound?

MULTIPLE CHOICE

I. Each of the following statements is followed by five responses. Choose the correct response in each case. For questions 1 and 2 use the same choices.

1. Which wave property causes a trumpet to sound different from a clarinet even if they are the same note with the same loudness?

a) reflection b) complexity of wave pattern

c) frequency d) amplitude

e)speed

2. Which wave property affects the intensity of sound?

a) loudness b) frequency

c)amplitude d) high pressure

e) low pressure

3. Which of the following frequencies is infrasonic?

a)12 Hz b) 60 Hz c) 1800 Hz

d) 2000 Hz e) 25 000 Hz

II. There are eight paragraphs in the text: give the title to each of the paragraphs; say what is the general idea of each of them.

III. Read text 4 without a dictionary and give its main idea.

Text 4. Alexander Graham Bell (1847-1922)

People remember Alexander Graham Bell as the inventor of the telephone. But he accomplished much more during his lifetime. Born in Scotland, in 1870 he emigrated with his parents to Canada, Ontario. Working with the staff at a school for the hearing impairs, Bell was successful in teaching his father’s techniques for helping deaf people to speak. With the assistance of Thomas Watson, Bell succeeded in creating a device that would transmit the human voice electrically.

In 1876, he transmitted his voice over a distance of 90 km. Also to his credit are the development of photophone, a proposal for using an implanted radium capsule to destroy cancerous tissues, and experiments that led to the construction of Canada’s first airoplane.

Bell died in Nova Scotia on August 2, 1922, at the age of 75. One of his former students paid him the following tribute: «Hearing is the deepest, the most humanizing sense which man possesses, and lonely ones all over the world have been brought into the pleasant ways of mankind because of Dr. Bell’s efforts».

UNIT 12

Grammar: 1. Subjunctive mood.

2. Use of Conditional Mood, Suppositional mood, Subjunctive I and Subjunctive II.

Texts: 1. London. Places of Interest in London.

2. Geometric Optics: Sources, Transmission and Reflection of Light

Section 1

GRAMMAR EXERCISES

I. Translate these sentences into Ukrainian, paying attention to conditional sentences of the first, second and third types.

1. If he asks me to help him, I shall be very glad to do it. 2. If he were in Lviv now, they would invite him to participate in the conference. 3. If you had come to the meeting yesterday, you would have taken part in the discussion of this question. 4. I f she comes home earlier, she will be able to see this film on TV. 5. If you studied harder, you would be able to pass your exams successfully. 6. If he had taken a taxi, he would have come in time. 7. If it were not so cold, I should go to the country. 8. If the air were composed only of nitrogen, the burning would be impossible. 9. Had I had time yesterday, I should have rung him up. 10. If you press the button, the device will start working.

II. Transform the sentences using Subjunctive II Present in the subordinate clauses.

Pattern: If you help me, I shall do this work in time.

If you helped me, I should do this work in time.

1. If Peter asks me, I shall help him 2. If they arrive on Friday, they will be able to see this exhibition. 3. If she comes tomorrow, I shall tell her about your proposition. 4. If they pass the exams next week, they will go to the seaside together. 4. If the rain stops, the children will go for a walk. 5. If I have money, I shall buy this dress.

III. Refer these sentences to the past.

Pattern: If he studied hard, he would pass the exam successfully.

If he had studied hard, he would have passed the exam successfully.

1. If he were more attentive, he wouldn’t make so many mistakes in his test. 2. If he knew English better, he would translate at the conference. 3. If I had the chance to visit London, I would see all the places of interest there. 4. If I received any information about it, I should let you know. 5. If Peter knew their address, he would write them a letter. 6. If I were in Kyiv now, I should see this exhibition.

IV. Paraphrase the following sentences, as in the patterns.

Pattern 1: It’s a pity he is so absent-minded.

I wish he were not so absent-minded.

Pattern 2: Unfortunately, I didn’t tell her about it..

I wish I had told him about it.

1. It’s a pity he is not here. 2. It’s a pity she is ill. 3. It’s a pity they don’t know German. 4. It’s a pity I am very busy now. 5. Unfortunately, she doesn’t know about our arrival. 6. I am sorry I can’t use the computer. 7. Unfortunately, I have no friends. 8. It’s a pity I can’t go to the theatre with you.

1.1 am sorry I didn’t translate this article. 2. It’s a pity I didn’t see this film. 3. Unfortunately, they were not there at that moment. 4. It’s a pity they didn’t invite me to their farewell party. 5.1 am sorry I didn’t let her take my dictionary. 6. It’s a pity they couldn’t get this book. 7. I am sorry I said this.

V. Translate the sentences, in which Suppositional Mood (or

Subjunctive I) is used.

1. It is necessary that they should arrive in time. 2. It was recommended that all should leave the room. 3. It is ordered that you (should) be there at 5 o’clock. 4. It was desirable that they start in the morning. 5. It is suggested that this work be done by Peter.

1. He recommended that I should start learning English from listening to the radio. 2. They insisted that they should come later. 3. She suggested that everybody should go to the park. 4. He demanded that I should show him my bag. 5. The teacher ordered that we start translating the new text without using the dictionary.

Section 2

Text 1. LONDON

London is the capital of Great Britain, its political, economic, commercial and cultural centre. It is also the greatest port of Great Britain. The city is situated on both banks of the river Thames in the South-East of England.

London is the fifth biggest city in the world after Tokyo, Mexico, Peking (Beijing) and New York. It occupies 1,863 square kilometres and stretches for nearly 30 miles from north to south and for nearly 30 miles from east to west. The population of the city is about 9 million people which makes nearly one fifth of all inhabitants of England.

Modern London is a city, which has never been planned and which has grown during the past twenty centuries. It is a city which arose from a number of towns and villages which had merged into one another but have not altogether lost their identity. Kennigston, Hampstead, Chelsea, Greenwich and many others could not just be called «districts» of London. Each of them is now a new town, each is architecturally different from the others, has its own main street or square, shopping centre and communal life.

Office

Actually there are several Londons. First, there is the City of London, its oldest part, which is about two thousand years old. The name «London» is Celtic in origin. In the first century when London was just a village, the Romans built their «Lond- inum» there. Many monuments of London’s history can be seen in the City. It is about one square mile in area and only a few thousand people live there. But it contains the Bank of England, the Stock Exchange, and the headquarters (offices) of many insurance and trading companies. In the evening the City is completely empty. But one street in it is busy day and night. This is Fleet Street, in and around which nearly all the important newspapers and press agencies have their offices.

Three other parts of London are: the West End, the East End and Westminster. The kings and queens live about two miles up the river Thames in Westminster, and all those who were connected with the court lived in that area. By the middle of the 16th century the district was already lined on with the houses belonging to nobility. The area around the royal court is known to be called the «West End». It is here that all the historic palaces are, as well as the famous parks: St.Jame’s Park, Green Park and Hyde Park with Kensington Gardens.

The busiest part of the West End, however, lies to the north and west of royal palaces and parks. This is the area of big department stores and all kinds of other shops — in Oxford Street, Regent Street, Bond Street. It is in the West End that most colleges and schools of the University of London are centred. It is here that nearly all the great public art collections of London as well as the best theatres, museums and restaurants are to be found.

London is the city of great contrasts. The City also expanded to the east, but the East End is very different from the West End. It is inhabited mainly by people whose life and work concentrate around the river, that is around the Port of London.

COMPREHENSION TEST

I. Read these sentences containing the information about London and say whether this information is true or false. Supply your answers with the phrases (see p. 96).

1. London is the third biggest city in the world. 2. The population of London is about one million. 3. London was built by the Romans in the fifth century. 4. Modern London is a city which has been carefully planned. 5. The City of London stretches for about 30 km from north to south and for about 30 km from west to east. 6. The City is the busiest and the most inhabited part of London. 7. The area around the royal court is known as the East End. 8. There are many theatres and museums in the East End.

II. Read the text below and be ready to speak with your groupmates about it.

Places of Interest in London

If you have the chance of visiting London you certainly should see its places of interest, which are very numerous. It is advisable that you should start the sightseeing tour of London from St. Paul’s Cathedral, which stands in the very heart of the city. It contains many tombs. Among these buried in it are admiral Nelson and the Duke of Wennington, who won the battle of Waterloo.

Near the Thames you can see the Palace of Westminster commonly called the House of Parliament. In one of the towers of the palace there is a clock. It is Big Ben. Buckingham Palace is the winter residence of the Queen.

There is a large old church near the Houses of Parliament. It is Westminster Abbey. In it the kings and queens are crowned. Many kings, queens, and other people who have brought fame to England have been buried here, Isaak Newton being one of them. Here we can see the tomb of the Unknown Soldier. On the way from St.Paul’s Cathedral to the Westminster Abbey you should visit Trafalgar Square and admire the Nelson Column there.

The Tower of London, a fortress built hundreds of years ago, is a museum now. It contains a collection of weapon. In one of the towers we can see the Queen’s crown and many other valuable things. Among other places of interest in London are The National Gallery and the British Museum.

III. Read this dialogue. Imagine that it is you and your friend but not the main characters who have just arrived in London. Would you say the same things and act in the same way if you were them? Role- play the situation.

The situation is as follows: Oksana Tkatch and Ihor Koval, two young scientists working at their research projects at Lviv Physico-Mechanical Institute, came to London to take part in an international scientific conference devoted to the problems of Strength of Materials. They have just arrived at London airport, where they are met by Steve Stanley, a young physicist from the University of London, a member of the Organizing Commettee.

At the airport.

S. —Excuse me, are you partici pants o,f the conference on the problems of Strength of Materials?

O. — Yes, we are.

S. — Let me introduce myself. I’m a representative of the Organizing Committee of this conference. My name is Steve Stanley.

T. — Glad to meet you, Mr. Stanley. My name is Ihor Koval, and this is my colleague, Oksana Tkach. We both are from L'viv.

S. — Glad to meet you, Oksana and Ihor. I’ve heard much about your ancient city and about its famous schools of physics and mathematics. You are welcome to London.

— It’s my first visit here, and I’ve dreamt about it all my life.

S. — How was the flight?

T. — Everything was wonderful. And the weather’s fine in London today, isn’t it?

S. — Oh, yes, it’s a lovely day.

In the bus, on the way to the hotel

S. — What are you going to do today?

— Are there any sessions at the conference today?

S. —No, only arrival and registration of the partici pants.

— Oh, then we have the whole day at our disposal. Very nice!

— We would like to see all the places of interest in London, to go everywhere.

S. — I think it’s impossible to see everything and to go everywhere in London in one day. If I were you I should study the map of London and decide what places to visit first. By the way, I’ve got a map of London here with me. Please look at it and tell me what places of interest you are going to see. (They all look at the map of London).

I. — Oh, there are so many places of interest in London. Now I see that it really is very difficult to see everything in one day.

— It’s even difficult to decide where to go first. Lon

don is so big. By the way, how big is it?

S. — London is one of the biggest cities in the world. It stretches about thirty miles long and about as many miles wide.

— And we are used to measuring the distance in the SI units of measurement.

S. — Then it’s about 48 kilometres.

— Now I see that it’s really impossible to see all the places of interest in London in one day.

S. — Right you are. In my opinion we’d better begin with the West End, from Trafalgar Square. It’s the centre of London and the best starting point for our tour of the capital.

— We’ll get settled at the hotel and then let’s go to Trafalgar Square.

S. — Agreed. An hour later, in Trafalgar square, then in Picadilly Circus.

S. — Now we are in Trafalgar square.

— That’s the Nelson Column in the centre, isn’t it? It’s so tall!

S. — Yes, that’s a monument to Admiral Nelson for his victories in the war against Napoleon. The large platform at the foot of it is often used by all sorts of speakers. You see, the square is a place for all sorts of meetings and demonstrations.

— Is that The National Gallery there on the left?

S. — Yes, but we shall go there another day. It’s getting dark, so we’d better go and see Picadilly Circus which is very beautiful in the evening.

— The Circus is not very large, but it’s very pictur esque.

S. — Six streets lead into the Circus. There is Regent Street, one of London’s most fashionable shopping centres.

— And this street leading off Picadilly Circus is Shaft esbury Avenue, isn’t it?

S. — Right you are. This is Shaftesbury Avenue, leading in the direction of Soho.

— I’ve read somewhere that Soho is the entertain ment centre of London.

S. — Yes, you will find almost everything there: music- halls, night-clubs, restaurants. But it’s late already, you’d better return to the hotel and get acquainted with other participants of the conference staying at your hotel.

— You are quite right.

Section 3