SCHEDULE XXVII
OPERATIONS INVOLVING HIGH NOISE LEVELS
1. Application:--- This Schedule shall apply to all operations in any manufacturing process having high noise level.
2. Definitions:--- For the purpose of this schedule,---
(a) “I” means any unwanted sound.
(b) “High Noise Level” means any noise level measured on the A-weighted scale is 90 DB or above.
(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 a reference pressure of 20 x 10-6 newtons per square metre of 0.0002 dynes per square centimetre 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 decible in abbreviated form in dB.
(d) “Frequency” is the rate of pressure variations expressed in cycles per second or hert.
(e) “dBA” refers to sound level in decibels as measured on a sound level meter operation on the A-weighting network with slow meter response.
(f) “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.
3. Protection against noise:--- (1) In every factory, suitable engineering, control or 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 Exposures in Cases of Continuous Noise
|
Total time of exposure (continuous or a number of short term exposures) per day, in hours |
Sound pressure level in dBA |
|
8 |
90 |
|
6 |
92 |
|
4 |
95 |
|
3 |
97 |
|
2 |
100 |
|
1 1/2 |
102 |
|
1 |
105 |
|
3/4 |
107 |
|
1/2 |
110 |
|
1/4 |
115 |
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 extra-polation on a proportionate basis.
TABLE - 2
Permissible Exposure Levels of Impulsive or Impact Noise
|
Peak sound pressure level in dB |
Permitted number of impulses of impacts per day |
|
140 |
100 |
|
135 |
315 |
|
130 |
1,000 |
|
125 |
3,160 |
|
120 |
10,000 |
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.
(2) For the purposes of this Schedule, if the variations in the noise 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 I would apply. In other cases, the noise level 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 fractions
C1 C2 Cn
---+ ---+ --- exceeds unity,--
T1 T2 Tn
Where the C1, C2, etc indicate the total time of 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 produce the noise exposure to the levels specified in sub-rule (1) by reasonably practicable engineering control or administrative measures, and each worker so exposed shall be provided with suitable ear protectors as 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 work by worker cannot still attenuate the noise reaching near his ear, determined by substracting the attenuation value id 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 exceed the permissible levels specified in sub-paragraph (1), there shall be m 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 maximum permissible exposure levels specified in the sub-rule (1) shall be subjected to an auditory examination by a certifying surgeon within 14 days of his first employment and there he shall be re-examined at least once after in every 12 months. Such initial and periodical examinations shall include tests include determination of auditory thresholds for pure tones of 125, 250, 500, 1000, 2,000, 4,000 and 8,000 cycles per second.