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