Schedule H (xxiv)

OPERATIONS INVOLVING HIGH NOISE LEVELS

1. Application-This Schedule shall apply to all operations in any manufacturing processes which

have high noise levels.

2. Definitions : For the purpose of this Schedule-

(a) "A-weighting" means making graded adjustments in the intensities of sound of various

frequencies for the purpose of noise measurement, so that the sound pressure level

measured by an instrument reflects the actual response of the human ear to the sound

measured;

(b) "dBA" refers to 'sound level in decibels as measured on a sound level meter operating

on the A-weighting network with slow meter response;

(c) "decibel" means one-tenth of "Bel" which is the fundamental division of a logarithmic

scale used to express the ratio of two specified or implied quantities, the number of

"Bels" denoting such a ratio being the logarithm to the base of 10 of this ratio. The noise

level (or the sound pressure level) corresponds to reference pressure of 6 x 10-6 N/m2 or

0.0002 dynes per square centimeter which is the threshold of hearing, that is, the lowest

sound pressure level necessary to produce the sensation of hearing in average healthy

listeners. The decibel in abbreviated form is dB;

(d) "first employment" shall mean first employment in areas where the noise exceeds the

maximum permissible exposure levels specified in sub-paragraph (1) of paragraph 3 and

shall also include re-employment in the said areas following any cessation of

employment for a continuous- period exceeding three calendar months;

(e) "frequency" is the rate of pressure variations expressed in cycles per second or hertz;

(f) "high noise level" means any noise level measured on the A-weighted scale is 90 dB or

above; and

(g) 'noise" means any unwanted sound.

3. Protection against noise- (1) In every factory, suitable engineering control administrative

measures shall be taken to ensure, so far as is reasonably practicable, that no worker is

exposed to sound levels exceeding the maximum permissible noise exposure levels specified

in Tables 1 and 2.

TABLE - 1

PERMISSIBLE EXPOSURE IN CASES OF CONTINUOUS NOISE

Total time of exposure (continuous or a number

Sound pressures level in dBA

of short-term exposure) per day, in hours

8 90

6 92

4 95

3 97

2 100

1-1/2 102

1 105

¾ 107

½ 110

¼ 115

Notes - (1) No exposure in excess of 115 dBA is to be permitted.

(2) For any period of exposure falling in between any figure and the next higher or lower

figure as indicated in column 1, the permissible sound pressure level is to be

determined by extrapolation on a proportionate basis.

TABLE - 2

PERMISSIBLE EXPOSURE LEVELS OF IMPLOSIVE OR IMPACT NOISE

Permitted number of impulses or

Peak sound pressure level in dB

impacts per day

140 100

135 315

130 1000

125 3160

120 10000

Notes - (1) No exposure in excess of 140 dB peak sound pressure level is permitted.

(2) For any peak sound pressure level falling in between any figure and the next

higher or lower figure as indicated in Column 1, the permitted number of impulses

or impacts per day is to be determined by extrapolation on a proportionate

basis.For the purposes of this Schedule, if the variations in the noise level involve

maxima at intervals of one second or less, the noise is to be considered as a

continuous one and the criteria given in Table 1 would apply. In other cases, the

noise is to be considered as impulsive or impact noise and the criteria given in

Table 2 would apply.

(3) When the daily noise exposure is composed of two or more periods of noise

exposure at different levels their combined effect should be considered, rather

than the individual effect of each. The mixed exposure should be considered to

exceed the limit value if the sum of the fraction (C1+C2 ) /(T1+T2)=(Cn/Tn) excess

unity-

where the C1, C2, etc. indicates the total time or actual exposure at a

specified noise level and T1, T2, etc. denote the time of exposure permissible at

that level. Noise- exposure of less than 90 dBA may be ignored in the above

calculation.

(4) Where it is not possible to reduce the noise exposure to the levels specified in

sub- rule (1) by reasonably practicable engineering control or administrative

measure, the noise exposure shall be reduced to the greatest extent feasible by

such control measures and each worker so exposed shall be provided with

suitable ear protectors so as to reduce the exposure to noise to the levels

specified in sub-rule (1).

(5) Where the ear protectors provided in accordance with sub-paragraph (2) and worn

by a worker cannot still attenuate the noise reaching near his ear, as determined

by subtracting the attenuation value in dBA of the ear protectors concerned from

the measured sound pressure level, to a level permissible under Table 1 or Table

2 as the case may be, the noise exposure period shall be suitably reduced to

correspond to the permissible noise exposure specified in sub- paragraph (1).

(6) (a) In all cases where the prevailing sound levels exceeds the permissible levels

specified in sub-paragraph (1) there shall be administered an effective

hearing conservation programme which shall include among other hearing

conservation measures, pre-employment and periodical auditory surveys

conducted on workers exposed to noise exceeding the permissible levels,

and rehabilitation of such workers either by reducing the exposure to the

noise levels or by transferring them to places where noise levels are

relatively less or by any other suitable means.

(b) Every worker employed in areas where the noise exceeds the maximum

permissible exposure levels specified in sub-rule (1) shall be subjected to

an auditory examination by a Factory medical officer within 14 days of his

first employment and thereafter, shall be re- examined at least once in

every 12 months. Such initial and periodical examinations shall include tests

which the Factory medical officer may consider appropriate, and shall

include determination of auditory thresholds for pure tones of 125, 250,

500, 1000, 2000, 4000 and 8000 cycles per second.