Presentation on Noise Pollution Ref: http://..

1. TELANGANA STATE FORESTACADEMY DULAPALLY, HYDERABAD
Dr. N. Sai Bhaskar Reddy | Director,The Earth Center, saibhaskarnakka@gmail.com
28th Dec ’17
Presentation 1

3. decibel scale (dB) - a ratio of two pressures
(Note : 10,000 microbars can cause immediate physical damage.)
•Sound Pressure Level - expresses the magnitude of volume or a sound (dB)
Note:The avg. person will perceive a high-pitch sound to be louder than a
low pitch sound with the same SPL. (see fig. 14.5 under sound-level
measurements in phons)

4. Sound Intensity (W/m2) - is proportional to the square of the root mean square (rms) value of a sound
pressure or SPL
(Note :for every 10 dB increase in SPL, there is a 10 fold increase in sound intensity.)
•Frequency Weighting Networks- noise is broken down to bands of low-medium-high frequency. “A-
weighted” network filters out low and high frequency where human ears is less efficient. [dBA is a.k.a A-
weighted decibels]
[Refer to p.464 in text fig. 14.3]
Sound Level (SL)- Sound Level measurement over a period of time. i.e. L90=75 dBA means 90% of the
time sound level exceeeded 75 dBA.

5. Sound Exposure Level (SEL) - provides a basis for computing noise events of variable durations which matches
a person’s impression of noise. It is standardized to 1 sec.
•Equivalent Sound Level (Leq)- is is the average or constant SPL over the period of interest. [i.e. Leq(8) is the
average for an 8 hr. period.]
•Day - Night Sound Level (DNL)- Leq(24) with a 10-dBA penalty for night time which is more annoying.
[Note: Noise can cause damage to our irritability, anxiety, stress and other emotional symptoms.]
TemporaryThreshold Shift (TTS)- Temporary hearing loss (approx. 1 month)
Noise -induced permanent threshold shift (NIPTS) - loss of hearing with no chance of recovery

6. less than 80 dBA -no hearing loss
•80 to 130 dBA -TTS hearing loss is noticeable
•50 % of people exposed to 95-dBA will experience NIPTS (permanent hearing loss)
•150 dBA or greater- can physically rupture the human eardrum.
(Note: 1 hr. of 100 dBA can produceTTS whereas 8 hours of 95 dBA over 10 years may cause NIPTS)
B
B
A
D
10X log
D
ASL S 

14. Area Code Category of Area/Zone Limits in dB(A) Leq*
Day Time Night Time
(A)
(B)
(C)
(D)
Industrial area
Commercial area
Residential area
Silence Zone
75 70
65 55
55 45
50 40
Note: -1. Day time shall mean from 6.00 a.m. to 10.00 p.m.
2. Night time shall mean from 10.00 p.m. to 6.00 a.m.
3. Silence zone is defined as an area comprising not less than 100 meters around hospitals, educational institutions and courts. The silence zones are zones, which are
declared as such by the competent authority.
4. Mixed categories of areas may be declared as one of the four-abovementioned categories by the competent authority.
*dB (A) Leq denotes the time weighted average of the level of sound in decibels on scale A which is relatable to human hearing.
A “decibel” is a unit in which noise is measured.
“A” in dB (A) Leq, denotes the frequency weighting in the measurement of noise and corresponds to frequency response characteristics of the human ear.

15. Sound Source dB(A)* Response Criteria
Carrier Deck Jet Operation
__
__ 150 Painfully Loud
Jet Takeoff (200 feet)
__
__ 140 Limit Amplified Speech
Discotheque, Auto horn (3 feet) __
__
130 may Maximum Vocal Effort
Riveting Machine 120 Very Annoying
Jet takeoff (2000 feet) Hearing Damage (8 hours)
Shout (0.5) feet 110 Annoying
N.Y. Subway Station
__
__ 100 Telephone use difficult Intrusive
Heavy Truck (50 feet)
__
__ 90 Quiet
Pneumatic Drill (50 feet) __
__
80 Very Quiet
Freight Train (50 feet) __
__
70 Just Audible
Freeway Traffic (50 feet) __
__
60 Threshold of Hearing
Air Conditioning Unit (20 feet Light Auto Traffic (50 feet) __
__
50
Living Room __
__
40
Bedroom 30
Library 20
Soft Whisper (15 feet) 10
Broadcasting Studio 0