How to Ensure Compliance with Noise Exposure Limits?

S

samsung

#1
Exposure to high noise is a significant health hazard and as such there are regulatory requirements for control on noise or atleast workers' exposure to noise within the prescribed limits.

What I'm confused about is the exposure limit v/s noise level. Here's an example to clarify my question - if the noise level is 95 dBA, the maximum prescribed limit for human exposure is 4 Hrs. I'm not sure of the exact meaning of this requirement and thus have the following queries:

a) Is it permissible for a worker to work for 4 hours a day at 95 dBA without hearing protectors?

b) Is it permissible for a worker to work for 4 hours at 110 dBA with hearing protectors that provide 15 dBA noise attenuation?

c) or after using the above said hearing protectors, can a worker be made to work for 8 hours in a 95 dBA noise environment?

Before putting up here, I went through the noise rules, searched the internet and other resources but the confusion still prevails.

Request your opinions/comments on the interpretation of this regulatory requirement.

Thanks.
 
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J

Jason PCSwitches

#2
I feel that this should be a matter of what I perceive as common concern for our human counterparts. Anyone subjected to abnormal levels of audio frequencies should be required to don protection regardless of a particular industry guideline.

Personally, I've adopted the approach of treating each environmental risk factor as if I were subjecting my own children to the environment. How would I protect them - as such, we should treat all personnel in the same manner. While that may appear to be over the top, we should treat our fellow man in the same regard, as much as possible.
 
#3
Hi

The numbers you have given are for factory workers and I am not sure if 95 dbA is allowed for 8 hours working. It should be 85 dBA. Indeed these levels and exposure times are safe boundaries to work without any special precautions to avoid any long term effect. i.e. one can work for 8 hrs a day 5 days a week without ear muffs/ear plugs when he is exposed to a sound level of less than 85 dBA, week after week, year after year without much of an effect on his hearing (i.e. the probability of the worker affected by hearing impairment in the long term is negligible). As the sound level increases the allowed time of exposure decreases to avoid long term effects. But in practice, as a precaution, workers are expected to wear a ear muff/ear plug if they work in areas with more than 85 dBA sound levels. Of course the best way is to reduce the sound level by design or engineering controls and bring the level to less than 85 dBA.

With kind regards,

Ramakrishnan
 
S

samsung

#4
Thanks Jason. I appreciate your concern and respect for the human environment and I very much support that any occupier should do more than what's minimum prescribed in the corresponding legislation. But purely from the compliance standpoint, I want to understand the requirement or say the intent of the requirement so as to make sure that whatever action I take to prevent the fellow beings from being exposed to high noise is right and will serve to protect their health. It's always not possible to reduce the source noise and whatever best one can do is to limit the exposure and provide the fellows with protective equipment. So the question is how do I know that I have done well or atleast what I was supposed to be doing.
 
S

samsung

#5
Hi

The numbers you have given are for factory workers and I am not sure if 95 dbA is allowed for 8 hours working. It should be 85 dBA. Indeed these levels and exposure times are safe boundaries to work without any special precautions to avoid any long term effect. i.e. one can work for 8 hrs a day 5 days a week without ear muffs/ear plugs when he is exposed to a sound level of less than 85 dBA, week after week, year after year without much of an effect on his hearing (i.e. the probability of the worker affected by hearing impairment in the long term is negligible). As the sound level increases the allowed time of exposure decreases to avoid long term effects. But in practice, as a precaution, workers are expected to wear a ear muff/ear plug if they work in areas with more than 85 dBA sound levels. Of course the best way is to reduce the sound level by design or engineering controls and bring the level to less than 85 dBA.

With kind regards,

Ramakrishnan
Infact 95 dBA exposure (to continuous noise) is allowable only for 4 hours a day in a manufacturing environment. I have attached the relevant part of the factory rules that allow 8 hours of exposure to 90 dBA noise level in a day. But as the noise levels go up, the exposure is exponentially lowered and at 105 dBA, the permissible exposure time is just an hour a day. My question is - can a worker be allowed to work for 8 hours a day at 105 dBA while wearing hearing protectors designed to attenuate the noise level by 15 dBA (effective exposure being 90 dBA)?

Thanks.
 

Attachments

Last edited by a moderator:

somashekar

Staff member
Super Moderator
#6
Infact 95 dBA exposure (to continuous noise) is allowable only for 4 hours a day in a manufacturing environment. I have attached the relevant part of the factory rules that allow 8 hours of exposure to 90 dBA noise level in a day. But as the noise levels go up, the exposure is exponentially lowered and at 105 dBA, the permissible exposure time is just an hour a day. My question is - can a worker be allowed to work for 8 hours a day at 105 dBA while wearing hearing protectors designed to attenuate the noise level by 15 dBA (effective exposure being 90 dBA)?

Thanks.
No.
What I gather after reading This
ILO says this :
"workers should not be exposed to noise levels above 95 dB for more than four hours per day. Exposed workers should be provided with ear protection while exposed at this level and rotated out of the noise areas after four hours of continuous work."
Goes to say that if the noise level is 95dB, two things are requirement:
1. Protection
2. Not more than continuous 4 hours work with protection when noise is 95 dB.

At 90 dB 8 hour work is permissible
At 105 dB protection must be provided and not more than 1 hour work is permissible. Even if the protection gets the effective noise down to 90 dB to the person, he must be rotated out every one hour.
 
Last edited:
S

samsung

#7
At 90 dB 8 hour work is permissible
At 105 dB protection must be provided and not more than 1 hour work is permissible. Even if the protection gets the effective noise down to 90 dB to the person, he must be rotated out every one hour.
I'm inclined to agree with your point and believe that it's practically not possible to work in a 105 dBA work environment with naked ears but the following rule (given in my previous post attachment) makes the things little ambiguous:

"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 exposures specified in sub-paragraph (1)."

According to this and for the purpose of calculating the effective noise (reaching near the ears), the protection provided by the hearing aids is to be subtracted from the measured value. If the difference of the two values falls within the limits, then it's OK for the worker as well as for the regulators?

Not sure if I understood it correctly.
 

ScottK

Not out of the crisis
Staff member
Super Moderator
#8
According to this and for the purpose of calculating the effective noise (reaching near the ears), the protection provided by the hearing aids is to be subtracted from the measured value. If the difference of the two values falls within the limits, then it's OK for the worker as well as for the regulators?

Not sure if I understood it correctly.
In the USA this would be correct.

Per OSHA
When employees are subjected to sound exceeding those listed in Table G-16, feasible administrative or engineering controls shall be utilized. If such controls fail to reduce sound levels within the levels of Table G-16, personal protective equipment shall be provided and used to reduce sound levels within the levels of the table.
It's simply subtracting the noise reduction Rating (NRR) of the PPE from the actual time weighted average noise level.

For example, If your time weighted average is 95 dB over 8 hours and you use Noise Reduction Rating 15 dB ear plugs, then your people may easily spend an 8 hour shift in the area.

The most common ear plugs I've seen have an NRR of 25 or more.
 
S

samsung

#9
In the USA this would be correct.

Per OSHA

It's simply subtracting the noise reduction Rating (NRR) of the PPE from the actual time weighted average noise level.

For example, If your time weighted average is 95 dB over 8 hours and you use Noise Reduction Rating 15 dB ear plugs, then your people may easily spend an 8 hour shift in the area.

The most common ear plugs I've seen have an NRR of 25 or more.
So my interpretation is close to what the rule says provided the degree of attenuation offered by the ear protectors is correctly measured or ensured. This is indeed a tough task to handle since NRR keeps decreasing with continued use of hearing aids and there's no way to measure there efficiency at site. So the best deal is to keep a wider safe margin.
 

ScottK

Not out of the crisis
Staff member
Super Moderator
#10
So my interpretation is close to what the rule says provided the degree of attenuation offered by the ear protectors is correctly measured or ensured. This is indeed a tough task to handle since NRR keeps decreasing with continued use of hearing aids and there's no way to measure there efficiency at site. So the best deal is to keep a wider safe margin.
Use a disposable ear plug and change them more than once a day. And provide training on how to insert them properly.

I worked in an adhesive tape converting facility for a number of years - imagine 25 rolls of duct tape being unrolled at high speed at the same time... per machine.
Even with a noise booth over the unwinder the operators on the rewind were exposed to over 105 dB unprotected for most of the day.

Disposeable ear plugs with a 25-33dB NRR, changed at break times, were perfectly acceptable to our insurance agency and to OSHA.
 
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