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11. Sound eLearn.Punjab

A safe level of noise depends on two factors: the level (volume) of the noise; and the period of
exposure to the noise. The level of noise recommended in most countries is usually 85-90 dB over
an eight-hour workday. Noise pollution can be reduced to acceptable level by replacing the noisy
machinery with environment friendly machinery and equipments, putting sound-reducing barriers,
or using hearing protection devices.

Activity 11.4: Develop an action plan to help you address any problem(s) with noise in your
workplace considering the following points:

1. Describe the problem(s).
2. What are the sources of the problem(s)?
3. Who are the people being affected?
4. Your suggestions for the solution.

11.6 Importance of Acoustics

The technique or method used to absorb undesirable For your information
sounds by soft and porous surfaces is called acoustic

protection.

Reflection of sound is more prominent if the surface is rigid and The phrase “blind as a bat” is a false
smooth, and less if the surface is soft and irregular. Soft, porous statement. Bats have some vision
materials, such as draperies and rugs absorb large amount using light, but when placed in pitch-
of sound energy and thus quiet echoes and softening noises. black rooms crisscrossed with fine
Thus by using such material in noisy places we can reduce the wires, they can easily fly around and
level of noise pollution. However, if the surface of classrooms unerringly locate tiny flying insects
or public halls are too absorbent, the sound level may be low for food. We usually assume that
for the audience. Sometimes, when sound reflects from the vision requires light but both bats and
walls, ceiling, and floor of a room, the reflecting surfaces are dolphins have the ability to “see” using
too reflective and the sound becomes garbled. sound waves. Research in science
and technology has developed “eyes”
15 that enable humans also to see using
sound waves.

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