The document discusses noise pollution, including its measurement, sources, effects, and control. It defines sound and noise, and explains how sound is measured in units such as frequency, intensity, and decibels. Common sources of noise pollution like traffic, construction, and industrial activities are identified. The effects of noise on hearing, health, communication, and work are outlined. Standards for acceptable noise limits in different areas are provided. Finally, the document discusses approaches to control noise pollution through modifications to noise sources, transmission paths, and receivers.

1. NOISE POLLUTION
By
Bibhabasu Mohanty
Assistant Professor
Department of Civil Engineering
SAL Institute of Technology & Engineering
Research

2. CONTENT
Measurement of sound, Sources,
Effects and control of noise pollution

3. THE NATURE OF SOUND
 Sound is a physical phenomenon that stimulates
the sense of hearing.
 Sound, a manifestation of vibration, travels in wave
patterns through solids, liquids and gases.
 Sound waves of equal amplitude with increasing
frequency from top to bottom.

4. SOUND PROPAGATION

5. AMPLITUDE AND WAVELENGTH PERIOD

6. BASIC TERMINOLOGY
 Frequency: Frequency is the no of
cycles repeated in unit time duration.
Its unit is cycle/sec or
Hz(1Hz=1Cycle/sec)
 Intensity:
Amount of sound energy
received / sec is known as intensity of
sound. Its Unit is decibel(dB).

7.  Decibel: Decibel is define as the
logarithm to the base 10 to ratio of two
intensities
Lt =10log10(I/I0)dB
 Where, I=Measured Intensity
 I0=Reference Intensity
 Lt=Level of noise in dB

8. SOUND NOISE
 Pleasant to hear  Unpleasant to hear
 Constant pitch  Constantly varying pitch
 Regular periodic motion  No regular periodic motion
 Produces meaningful  Produces no meaningful
communication communication
 Unit is Hertz (Hz)  Unit is decibel (dB)
Hz= cycle/sec. dB=10 log(intensity
measured/reference
intensity)

9. LEVELS OF NOISE
L = log10 Q/Q0 (bels)
 Q=Measured Intensity
 Q0=Reference Intensity
 L=Level of sound in Bels
1dB= 1/10 B
Hence, L = 10 log10 Q/Q0 (dB)

10.  When sound pressure is measured, Q0= 20 μPa.
Lp= 10 log10(Prms/ 20μPa)2
sound pressure is computed by squaring r.m.s value
or Lp= 20 log10(Prms/ 20μPa)
 When sound power is measured, Q0= 10 – 12 watts
Lw = 10 log 10 (W/10– 12)
 When sound intensity level measured , Q0= 10 – 12
W/m2
LI = 10 log 10 (I/10– 12)

12. SOUND LEVEL METER

13.  Sound level meters (SLMs) measure sound
pressure level and are commonly used in noise
pollution studies.
 Positioned
in desired location with no obstruction
from source and sound is taken.
 Basic
parts include microphone, amplifiers,
weighting networks and display reading in dB.

14.  This device performs three basic operations: -
 First,
microphone to convert the energy in the
sound into an electrical signal. When a sound
wave hits the microphone, it causes a
diaphragm.
 To vibrate, electronic signals, which are
proportional to the sound pressure causing the
vibration.
 Thirdly, this electronic network then provide
meaningful results transmitted through a visual
display.

16.  Internationally accepted three weighing scales
adopted.
 A,B and C.
A for human intensity to low intensity sound.
B for medium intensity sound.
C for human response to high intensity sound.

17. Rule of thumb when measuring noise levels
 The noise source being measured should be at
least 10 dB above the background (ambient)
noise.
 Keep the sound level meter as far away from any
large reflecting surfaces as you are from the
source that you are measuring.
 Allmeasurements are to be made with the
microphone at least 3 feet above the ground.

18. SOUND AND HUMAN HEARING
 People generally hear sounds between the
“threshold of hearing” and the “threshold of pain”.
 In terms of pressure, this is 20 μPa – 100 Pa.
 The decibel scale was developed from this fact and
makes numbers more manageable.
 The decibel scale generally ranges from
approximately 0 to 130.

19. HOW SOUND IS HEARD

20. HUMAN HEARING AND FREQUENCY
0 16 Hz 20 kHz 5 MHz

21. WHAT IS NOISE POLLUTION ???
 unwanted sound that penetrates the
environment
 any noise irritating to one's ear which comes
from an external source
 in relatives terms one’s enjoyment may be
pollution to other.
 sound which pleases the listeners is music and
which causes pain and annoyance is noise.
 noise affect us in hearing, ability to communicate
and behavior.

22. SOURCE OF NOISE POLLUTION
 Street traffic
 Rail traffic
 Road traffic
 Airplanes
 Constructions
 Indoor source (Radio, TV, AC, home appliances)
 Less maintained vehicles produce more sounds

23. NOISE STANDARDS
Area code Category of area Limits in dB
Day time Night time
A Industrial area 75 70
B Commercial area 65 55
C Residential area 55 45
D Silence zone 50 40
Day time: 6 am to 9 pm
Night time: 9pm to 6 am

24. SOUND LEVEL FOR HUMAN RESPONSE

25. EFFECTS OF NOISE POLLUTION
 Loss of hearing
 Annoyance
 Health effects
 Interference with communication
 Working efficiency

26. Loss of hearing – due to exposure of noise, which
termed as artificial hearing loss.
1. Noise induced temporary threshold shifts (NITTS)-
due to exposure to loud noise like bursting of
crackers. Recovered in a short period of time.
2. Noise induced permanent threshold shifts
(NIPTS)- because of exposure to loud noise for
long period time.

27. Annoyance – subjective matter for sound/noise.
 Someone may like classical music, it may annoy
others.
 Annoyance is felt about 75 to 85 dB.
 Blood vessel get constricted, breathing rate
affected.
Health effects –
Effects on physical health.
 Auditory effects- short time and long time effects.
Acoustic trauma due to high intensity impulsive
noise of about 150 dB or more.
 Non-auditory effects- exposure to loud noise
increase pulse rate and blood pressure change.

28. Effects on mental health- lack of conc. at high
noise level and mental disturbance.
Interference with communication – background noise
affect the efficiency of offices, schools and other
places where communication is vital importance.
 External sound also interfere with conversation
and use of telephone as well as enjoyment of
radio and TV.
 Maximum acceptable limit of noise 55dB.

29. Working efficiency – decrease the working efficiency
drastically. Experiments indicate that irregular
bursts of noise are more disruptive than steady
noise.
 Sound levels of 90 dB may interfere with the
performance of a task.
Other effects
 Sleep interference
 Personal comfort interference
 Effects on wild life
 Increased industrial accidents.

30. CONTROL OF NOISE POLLUTION
 Can never be eliminated completely, but it can be
controlled.
 Noise pollution can be controlled by paying
attention to one or all of the three elements
involved:

31.  Source :- can be modified by changing in design,
treatment of machine surface, noise source could
be stopped or operation limited to certain times.
 Transmission path :- sound insulating enclosure,
construction of noise barrier, absorbing materials
along the path.
 Receiver :- altering the work schedule, by provision
of ear protection.

32. Others steps to control noise pollution
 Noise pollution (Regulation and control) Rules,
2000.
 Vehicular noise can be controlled by proper
maintaince.
 Industrial noise controlled under the factory act,
1948.
 Legal laws to control blaring loudspeakers,
playing of music system at loud level.
 Use of better technology in design of systems
like fan, AC, washing machines and refrigerators.

33.  Proper town planning can help in avoiding noise
pollution (construction from major noise sources).
 Proper zoning and separation of buffers.
 Thick and high vegetation can absorb much noise.
 Aerodrome should be located away from the city.
 Aeroplanes should take off in direction readily away
from the city.

34. Noise barrier: Highway in Melbourne, Australia