Friday, November 30, 2012

The unit by which the loudness for HSC Exam

Set-2
Read the following passage and answer the questions :
The unit by which the loudness of sound is measured is called a decibel. According to the UN, the normal tolerable, pleasant level, is simply called sound. But when it is sharp and harsh to the ears it becomes noise. Serious harm can be caused to people if they are regularly exposed trod sounds exceeding 70 decibels. Because of the growth of urban population and the increasing use of machines in our everyday life there has been a general increased in the level of sound around us. On an average, people in the cities are exposed to sounds ranging from 30 to 90 decibels or even more. A study in Japan has found that housewives who live in the city were exposed to almost the same amount of sound that a factory worker was exposed to at his her workplace. The occupations that the study found to be the noisiest were factory work, truck driving and primary school teaching. Many developed countries are trying to control sound pollution by careful town planning and developing public awareness. In Holland schools are not allowed near airports and houses which are situated near airports are provided with special types of insulation to limit the sound heard inside the buildings.
5. Write short answer to the following questions: 5
(a) What is the view of the UN about the tolerance limit of sound?
(b) What is a decibel?
(c) When does sound become a noise?
(d) Why does the Japanese study consider the primary school environment noisy?
(e) What is the range of sound in the cities of Bangladesh?

6. Fill in the gaps with suitable words.

We (a) — the loudness of sound by a unit called a decibel. Sound is tolerable but noise is (b) —. The level of sound around us has (c) —. Growth of population and increasing use of machines (d) — responsible for this. Many developed countries are controlling sound pollution in (e) — ways.
7. Summarise the causes and effects of sound pollution in five sentences. 5

8. On the basis of your reading of the passage, make short notes in each of the boxes in the flow chart, showing the measures taken by the developed countries. (No. 1 has been done for you). 5

1. town planning 2. 3. 4. 5. 6.
Ans. to the Ques. No. Set-2:
5. (a) According to UN the normal tolerance limit is 45 decibels.
(b) Decibels is the unit of sound
(c) if the sound goes beyond the limit of audibility, it becomes noise.
(d) The Japanese study finds that the primary school teaching is noisy because it exceeds the normal limit of audibility.
(e) The range of sound in the cities is from 30-90 decibels.
6. (a) measure (b) intolerable (c) increased (d) are (e) various
7. Summary:
Sound pollution is a threat to sound life. It makes life intolerable. The city dwellers are exposed to loud sounds. Factory work, truck driving and primary school teaching are noisy. It should be checked.
8. Flow chart:
1. town planning 2. developing public awareness 3. no school near air port 4. providing a special type of insulation to house 5. control of noise 6. using machines in marginal scale

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