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) “Noise” means any unwanted sound;
(b) “High noise level” means any noise level measured on the A-weighted scale is 90dB or above;
(c) “Desibel” means one-tenth of “Bel” which is the fundamental division, of a logarithmic scale used to express the ratio of two specific 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 or 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 listener. The decibel in abbreviated from is dB;
(d) “frequency” is the rate of pressure variations expressed in cycles per second or hartz;
(e) “dBA” refers to sound level in decibels as measured on a sound level metre operating on the ‘A-weighting net work with slow metre response.
(f) “A-weighting” means making graded adjustments in the intensities of sound of various frequencies for the purpose of noise measurements, 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 measure shall be taken to ensure, so far as reasonably practicable that no worker is exposed to sound levels exceeding the maximum permissible noise exposure levels specified the Tables 1 and 2.
Permissible Exposure in Case of continuous Noise
|
Total time of exposure (continuous or 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 |
Explanation. -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 high or lower figure as indicated in column 1 the permissible sound pressure level is to be determined by extrapolation on a proportionate basis.
Permissible Exposure levels for Impulsive of Impact Noise
|
Peak sound pressure level in dB |
Permitted number of impulses or impact per day |
|
140 |
100 |
|
135 |
315 |
|
130 |
1,000 |
|
125 |
3,160 |
|
120 |
10,000 |
Explanation. --- (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 impact 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 level involve maximum 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 functions
C1 C2 Cn
--- + -----+ ----- .... exceeds unit p---1
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 to reduce the noise exposure to the levels specified in sub-paragraph (1) by reasonably practicable engineering control or administrative measures, 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 b substracting the attenuation value in dBA of the ear protectors concerned from the measured should pressure level, to a level permissible under Table 1 or Table 2 as the case be, the noise exposure period shall be suitably reduced to correspond to the permissible noise exposures 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 administered an effective hearing conservation programme which shall include among other hearing conservation programme which shall include among other hearing conservation measures, pre-employment and periodical adult 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 place 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 Certifying Surgeon 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 Certifying Surgeon may consider appropriate, and shall include determination of auditory thresholds for pure tones of 125, 250, 500, 1,000, 2,000, 4,000 and 8,000 cycles per second.