PHYSIOLOGICAL
EFFECT OF NOISE
Today, I am going to discus in details the
physiological effect of noise on human body :
As we know that in the present era of mechanization noise
pollution is a big threat to the human life. The day to day growing
industrialization such as growth in motor vehicle industry, heavy mechanization
of mining industry, also depends on machine in daily life. Due to these reason
we should be aware of the effect of noise on our body. To know the effect
following Table will be effective :
Noise Level
|
Working Limit
|
85 db(A)
|
Warning
|
90 db(A)
|
Danger limit 8 hrs
|
93 db (A)
|
4 hrs
|
96 db (A)
|
2 hrs
|
115 db (A)
|
8 hrs (with ear Protection)
|
130 db (A)
|
(Threshold limit) For impulse noise of
short duration
|
140 db(A)
|
No Work
|
Note; 1.
Conventional Speech around 60 db (A).
2.
Lowest limit a human can detect is 1db (A).
3.
Level of protection : Low: L – for noise levels 85-100 db(A).
Medium : M - :……………100-110
db(A)
High : H-
………………110 -120db(A)
Extra High
: X -………… above 120
db(A).
PHYSIOLOGICAL EFFECT
·
More than 100 db(A) → Nausea, Stresses & physical
imbalance.
·
≥ 150 db(A) → Damage of permanent
hearing.
·
High noise level → Deaf more quickly.
·
Adverse effect depends upon → Pressure Level, frequency & time
exposure.
The normal human ear is sensitive to frequency between 20Hz. and 20000 Hz.. It is
most sensitive to frequency in the range of 2000 - 5000Hz. & progressively
less sensitive to the lower and higher frequency.
Normal speech lies between 300 to
500 Hz.
Continuous noise of 5000 Hz.
gradually loss of ability to hear called nerve deafness.
Hearing loss is greatest in 3000 to
6000 Hz.. Inner ear is affected.
Hearing loss starts in the
frequency range around 400 Hz. At high pressure mental disorientation, lack of
concentration, loss of working efficiency, accident density, personal
discomfort.
PERMISSIBLE NOISE LEVEL
IN INDIA, USA&UK
In the following Table the
comparative study of noise level limit at India ,USA, & UK are given for
ready reference :
INDIA
|
USA
|
UK
|
|||
Noise Level
|
Duration of
Exposure in (hr/Day)
|
Noise Level
|
Duration of
Exposure in (hr /Day)
|
Noise Level
|
Duration of
Exposure in (hr /Day)
|
85 db(A)
|
Unprotected
ear working limit
|
90 db(A)
|
8
|
88 db(A)
|
13
|
90 db(A)
|
Danger Limit 8
hrs
|
92 db(A)
|
6
|
90 db(A)
|
8
|
93 db(A)
|
4 hrs.
|
95 db(A)
|
4
|
93 db(A)
|
4
|
96 db(A)
|
2 hrs
|
97 db(A)
|
3
|
96 db(A)
|
2
|
115 db(A)
|
Not enter
without ear protection
|
100 db(A)
|
2
|
99 db(A)
|
1
|
130 db(A)
|
For impulse
noise for short time
|
102 db(A)
|
1⅟2
|
102 db(A)
|
30 min
|
140 db(A)
|
No work
|
105 db(A)
|
1
|
105db(A)
|
15 min
|
107 db(A)
|
¾
|
108 db(A)
|
7.5 min
|
||
110 db(A)
|
½
|
111 db(A)
|
4 min
|
||
115 db(A)
|
¼
|
114 db(A)
|
2 min
|
||
117 db(A)
|
1 min
|
||||
120 db(A)
|
30 sec.
|
||||
COMPUTATION OF NOISE DOSE TO A WORKMEN ARE AS FOLLOWS:
In order to compute the
noise dose of a workmen in a shift , NOISE EXPOSURE INDEX (NEI) is defined as rate
of actual exposure time at a certain level to the permitted exposure time that
is :
NEI
= C/T , Where C = actual time (measured in the mine on the job)
T = Permitted exposure time (As per Law
or directive)
If the noise level change during the
course of an employees work shift. NEI must be calculated for each different
noise level. The total or accumulative NEI, for that shift is then the sum
of all the individual’s NEI
i.e.
NEI = C1/T1 + C2/T2+………………….Cn /Tn
Where
C1………..Cn actual
exposure time for noise level 1 to N.
And
T1……………Tn permitted exposure time for noise level 1 to N.
A worker should be consider out of
compliance if his daily total NEI exceeds 19Unit). In practical terms this
shows that his actual exposure time has exceeded the permitted exposure time.
For example a worker is exposed to 2
hrs at 93 db(A) and remaining 6 hrs at 88 db(A).
Actual
Exposure -
exposure time as per law
2 hrs. -
93 db(A)- 4
hrs.
6 hrs -
88 db(A) - 13
hrs.
2 + 6 = 0.5+0.46 = 0.96
4 13
Which is
less than 1 so he could be safe.
FOR REDUCTION
OF NOISE LEVEL EXPOSURE FOLLOWING MEASURE HAS TO BE TAKEN:
1. Controlling
of time
2. Substitute
3. By
tightening down the loose parts.
4. Proper
lubrication.
5. Speed
rating.
6. Use
of silencer or suitable muffles.
Thank you pl. comment
