2.  Noise Pollution  Noise & Our Hearing  Level of Noise  Measurement of Noise  Classification of Noise  Sources of noise  Impacts of noise  Control of noise pollution  Conclusion

3. Noise is unwanted sound. Sound is a form of energy which is emitted by a vibrating body and on reaching the ear causes the sensation of hearing through nerves. Or we can say when the effects of sound are undesirable it termed as NOISE

4.  The inner ear of humans contains a snail-shaped structure called a cochlea that is lined with thousands of microscopic hairs. When sound vibrations enter the cochlea, they cause the tiny hairs to move back and forth. If strong vibrations blast into the cochlea, the hairs can be flattened and damaged.

5.  Sound is the quickly varying pressure wave travelling through a medium. When sound travels through air, the atmospheric pressure varies periodically. The number of pressure variations per second is called the frequency of sound.

6.  The response of the human ear to sound is dependent on the frequency of the sound. The human ear has peak response around 2,500 to 3,000 Hz and has a relatively low response at low frequencies.

7.  To express sound or noise in terms of Pa is quite inconvenient because we have to deal with numbers from as small as 20 to as big as 2,000,000,000. A simpler way is to use a logarithmic scale. As such, the loudness of sound is commonly expressed in decibel (dB).

8. Sound Levels and Human Response Common soundsNoise Level [dB]Effect Rocket launching pad, (no ear protection)180Irreversible hearing loss Carrier deck jet operation, Air raid siren140Painfully loud Thunderclap130 Jet takeoff (200 ft), Auto horn (3 ft)120Maximum vocal effort Pile driver, Rock concert110Extremely loud Garbage truck, Firecrackers100Very loud Heavy truck (50 ft), City traffic90 Very annoying Hearing damage (8 Hrs) Alarm clock (2 ft), Hair dryer80Annoying Noisy restaurant, Freeway traffic, Business office 70Telephone use difficult Air conditioning unit Conversational speech 60Intrusive Light auto traffic (100 ft)50Quiet Living room, Bedroom, Quiet office40 Library, Soft whisper (15 ft)30Very quiet Broadcasting studio20 10Just audible 0Hearing begins

9.  Sound Power  Sound Intensity  Sound Pressure

10.  If a sound source has a pressure of 2000µPa at 10m distance, compute: a) The sound pressure level in dB, b) The sound intensity in W/m 2, c) The sound power in W.

11. a) L p = 40dB b) I = 9.9x10 -9 W/m 2 c) W = 12.5x10 -6 W

12. 1) Community Noise/Environmental Noise 2) Occupational Noise a) Continuous Noise b) Intermittent Noise c) Impulsive Noise

13. It is also known as,  Environmental Noise  Domestic Noise  Residential Noise Sources:  Road, Rail, Air traffic  Construction and Public works  Restaurant, cafeteria etc.  Sporting events like motor sports  Play grounds  Parks

14. Sources:  Industrial Machinery includes,  Rotors, gears, electrical machines.  Combustion engines  Drilling, crushing  Pneumatic equipment

15. Occupational Noise Continuous Noise Impulsive Noise Intermittent Noise

16. It is produced by the machinery that operates without interruption e.g.  Pumps, Compressors and Processing equipments