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“Occupational Health & Safety”
“Master of Industrial Hygiene & Safety”
Department of Master of Industrial Hygiene & Safety
Institute of Science & Technology for Advanced Studies &
Research (ISTAR) Offering Post Graduate Interdisciplinary Programme
On The Behalf Of B.V.M Engineering College In Collaboration With University
Of Cincinnati, Ohio, U.S.A. & Sardar Patel University
Hardik Kalal
Sardar Patel Univesity
Vallabh Vidyanagar
2014
Institute of Science & Technology for Advanced Studies &
Research
Sardar Patel Center of Technology, Motabazar,Vallabh Vidyanagar
Anand -388120, Gujarat
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Noise Monitoring
A. Introduction
B. Statutory Provisions
C. Personal Noise Monitoring Data
D. Area Monitoring Data
E. Recommendation & Conclusion
A. Introduction:
Sound is what we hear. Noise is unwanted sound. The difference between sound and noise
depends upon the listener and the circumstances. Rock music can be pleasurable sound to one
person and an annoying noise to another. In either case, it can be hazardous to a person's
hearing if the sound is loud and if he or she is exposed long and often enough.
Sound is produced by vibrating objects and reaches the listener's ears as waves in the air or
other media. When an object vibrates, it causes slight changes in air pressure. These air
pressure changes travel as waves through the air and produce sound. To illustrate, imagine
striking a drum surface with a stick. The drum surface vibrates back and forth. As it moves
forward, it pushes the air in contact with the surface. This creates a positive (higher) pressure
by compressing the air. When the surface moves in the opposite direction, it creates a
negative (lower) pressure by decompressing the air. Thus, as the drum surface vibrates, it
creates alternating regions of higher and lower air pressure. These pressure variations travel
through the air as sound waves.
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Approximate Speed of Sound in Common Materials
Medium Sound
Velocity
(ft/s)
m/s
Air, dry (0°C and 0.76 mm Hg) 1,100 330
Wood (soft - along the fibre) 11,100 3,400
Water (15°C) 4,700 1,400
Concrete 10,200 3,100
Steel 16,000 5,000
Lead 3,700 1,200
Glass 18,500 5,500
Hydrogen (0°C and 0.76 m) 4,100 1,260
What are basic rules of working with decibel (dB) units?
The decibel [dB, and also dB(A)] is a logarithmic scale. For mathematical calculations using
dB units, we must use logarithmic mathematics. However, in our day-to-day work we do not
need such calculations.
The use of dB unit makes it easy to deal with the workplace noise level data provided we use
a set of simple rules as summarized in table.
Decibel (dB) basics
Change in dB Change in sound energy
3 dB increase Sound energy doubled
3 dB decrease Sound energy halved
10 dB increase Sound energy increased by factor of 10
10 dB decrease Sound energy decreased by factor of 10
20 dB increase Sound energy increased by factor of 100
20 dB decrease Sound energy decreased by factor of 100
How are noise levels added?
Sound pressure levels in decibels (dB) or A-weighted decibels [dB(A)] are based on a
logarithmic scale. They cannot be added or subtracted in the usual arithmetical way. If one
machine emits a sound level of 90 dB, and a second identical machine is placed beside the
first, the combined sound level is 93 dB, not 180 dB.
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Table shows a simple way to add noise levels.
Addition of Decibels
Numerical difference between
two noise levels [dB(A)]
Amount to be added to the higher of the
two noise levels [dB or dB(A)]
0 3.0
0.1 - 0.9 2.5
1.0 - 2.4 2.0
2.4 - 4.0 1.5
4.1 - 6.0 1.0
6.1 – 10 0.5
10 0.0
Step 1: Determine the difference between the two noise levels and find the corresponding
row in the left hand column.
Step 2: Find the number [dB or dB(A)] corresponding to this difference in the right hand
column of the table.
Step 3: Add this number to the higher of the two decibel levels.
For instance, using the example of two machines each emitting a noise level of 90 dB:
Step 1: The numerical difference between the two levels is 0 dB (90-90= 0), using the first
row.
Step 2: The number corresponding to this difference of 0, taken from the right hand
column, is 3.
Step 3: Add 3 to the highest level, in this case 90. Therefore, the resulting noise level is 93
dB.
When the difference between two noise levels is 10 dB(A) or more, the amount to be added
to the higher noise level is zero. In such cases, no adjustment factor is needed because adding
in the contribution of the lower in the total noise level makes no perceptible difference in
what people can hear or measure. For example if your workplace noise level is 95 dB(A) and
you add another machine that produces 80 dB(A) noise, the workplace noise level will still be
95dB(A).
Formulas to calculate noise exposure
1. Average noise exposure for area monitoring –
(10*LOG10(1/n*(10^(L1/10)+(10^(L2/10)+……….+(10^(Ln/10)))))
L =Measured noise exposure at different locations
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N = total number of readings
2. Dose calculation - 100*((C1/T1) + (C2/T2)+(Cn/Tn))
C1 = Actual time duration of noise exposure
T1 = Allowable time duration of noise exposure
3. Time weighted average (TWA) - 16.61*LOG10 (Dose/100) +90 (According to Factory
Act 1948 India and OSHA)
16.61*LOG10 (Dose/100) +85 (According to ACGIH)
4. Noise Reduction Rating (NRR) - (Actual Exposure – Allowable expos re)*2+7
B. Statutory Provisions:
In the 3rd Schedule under the Factories Act ‘Noise induced hearing loss’ (exposure to
high noise levels) is included as a notifiable occupational disease.
Schedule 23 u/r 102 of the Gujarat Factories Rules, defines high noise as 90 dBA or
more and requires that -
1. No worker should be exposed to high noise level.
2. Ear protectors should be given to workers if engineering control to reduce noise is not
possible and
3. Workers exposed to high noise should be auditory examined by a doctor within 14 days of
his first employment and thereafter re-examined once in every year.
Schedule 24 u/r 114 of the Maharashtra Factories Rules 1963 and Schedule 28 u/r 95
of the Tamil Nadu Factories Rules 1950 give tables of permissible levels that are reproduced
in Table:
Total time per day in hours Sound level dBA
8 90
6 92
4 95
3 97
2 100
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1.5 102
1.0 105
0.75 107
0.50 110
0.25 115
No exposure is permitted over 115 dBA.
Peak sound level in dB Permitted number of impulses or impacts per day
140 100
135 315
130 1000
125 3160
120 10000
No exposure is permitted over 140 dB peak sound level.
Under Schedule I (u/r 3) and Schedule VI (u/r 3A) of the Environment (Protection)
Rules, 1986, Noise standards are prescribed as given in Table:
Noise Standards (EP Rules)
Sch. III u/r 3 of the above rules prescribes noise levels in public areas as given in
below table.
Noise Level in public areas (EP Rules)
Area Category Noise level in dBA
Code Day Time
6 am to
9 pm
Night time
9 pm to
6 am
A Industrial area 75 70
B Commercial area 65 55
C Residential area 55 45
D Silence zone (100 m radius) 50 40
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D. AREA NOISE MONITORING
S.No. Location Area In Plant Condition
dBA
❶
dBA
❷
dBA
❸
Average
dBA
NRR Recommendation
1 Captive Power Plant
Not In
Use
60 58 63
60.82
1.Engineering control
2.proper maintenance
3.Enclosure
4.Vibration Absorber
5.Proper PPE
According NRR
2 Between BR2 &3 At Boiler House 95 88 90 92.04 17.10
Process Unit(3 Meter Away)
3 Nr. SSTD At BD1 70 68 73 70.82
4 Nr. SSTD At BD1-310 At BD3 81 84 83 82.84
5 MEE Plant At G.F 54 58 62 59.15
6 Incineration Plant At F.F 84 81 87 84.67
7 New RO Plant At G.F
Not In
Use
64 60 67 64.54
Utility Working Place/Control Room
8 Nr.Air Blower At ETP 102 98 96 99.40 31.80
9 BP 11 At Cepha utility 90 94 95 93.47 19.94
10 BP 3 At BD utility 85 87 82 85.12
11 BP 10 (Utility Block BD 3,4 85 89 83 86.40
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12 Nr.DG Set Room
Not In
Use
76 77 74 75.84
Other Location
13 Nr. Security Office 56 52 60 57.15
14 Nr. Ware House BD 62 66 68 65.98
15 Nr. Main Gate 60 65 58 62.04
Noise Reduction Rating is find out for 87 dbA level
E. RECOMMENDATION & CONCLUSION:
Prepare a schedule for Checking & maintenance of noise equipment.
Provide personal protective equipment to employee & give them training about how to use it & how to work in noisy area.
Regular checkup of audiometric testing of workers who exposed high noise.
It is observe that noise is not higher than limit.
Make enclose office in Boiler Area.
Prepare a schedule to checking & maintenance of noisy machine.
Increase the distance between the source and the receiver to reduce exposure.
