How Can We Effectively Assess Noise Risks in the Workplace? Seeking Your Ideas!

Dear All, I am planning to conduct a walkabout survey to assess the potential risk from noise. The aim is to identify possible activities or areas of significant noise exposure and determine if additional monitoring is necessary. Do you have any ideas regarding this?

Kind Regards,
Bipin Gautam

Noise Hazard Concerns at the Workplace

Noise hazard is one of the major concerns and challenges in our workplace at an international level. Please follow the links below, which provide more stringent guidelines. OSHA has given a brief overview of how to conduct noise surveys and who should conduct them.

- [Noise and Hearing Conservation Technical Manual Chapter: Section III: How do I evaluate noise exposure?](http://osha.gov) *[Link updated to site home]*

- [Noise and Hearing Conservation Technical Manual Chapter: Evaluation (App III:A-3)](http://osha.gov) *[Link updated to site home]*

- *[Link outdated-removed]*
*( [Search On Cite](https://www.citehr.com/results.php?q=Occupational noise exposure 1910 95) | [Search On Google](https://www.google.com/search?q=Occupational noise exposure 1910 95) )*

Note: Attached are the OSHA noise survey and analysis report, as well as the Measurement of Workplace Noise PDF files for your reference. Hope it helps. Keep in touch.

Regards

Noise Assessment and Control Measures

In addition to what Mr. Raghu has explained, you may refer to the Factories Act. It is a good idea to conduct a walk-through survey. This will draw your attention to noisy areas. The Factories Act considers a 90 dBA noise level and TLV limit for 8 hours of exposure. Once you identify the potential for improvement, you have to control the noise at its source through engineering controls, which include:

- Acoustic Enclosures
- Good Maintenance of Machines

Another way is through administrative controls when reducing the noise at its source is not possible:

- Isolation: Isolate the noisy area
- Job Rotation

You may conduct audiometry tests on employees with increased frequency and compare the results with the previous tests. If you need any more inputs, please let me know.

Thanks & Regards,
Sudhir

In addition to the points you have mentioned above, in situations where the noisy area cannot be avoided, such as working in quarries or being surrounded by noisy machines like big compressors and DG sets, it is advisable to use personal protective equipment, such as ear muffs and ear plugs, for the personnel working in those areas.

Thanks

Regards

Dear Murdhar, DG set is supposed to have an acoustic enclosure. If both the compressor and DG set are in one room, you may consider an acoustic room for both of them together.

Personal Protective Equipment (PPE)

Personal Protective Equipment (PPE) should be used as a last line of defense. You should not rely solely on PPE.

Thanks & Regards,
Sudhir

Dear Sudhir, An acoustic enclosure for noisy machines is designed to prevent noise from reaching external persons, rather than those working near the machines. Operators and maintenance technicians, who need to frequently visit the machines to check their normal operation, cannot avoid the noise generated by them. Therefore, it is essential for them to use personal protective equipment such as ear muffs and ear plugs.

Noise Level Specifications

Typically, during the design stage of machine specifications, the permissible noise level is set to be less than 90 dB (decibels). However, factors such as aging, faulty design, improper balancing, among others, can contribute to higher noise levels than the specified limit. It is the responsibility of operators and maintenance technicians to identify the causes of these high noise levels and take necessary steps to eliminate them.

I hope this clarifies the situation.

Thank you.
Regards

Sudhir is right that the noise level has to be controlled at the source. If for any reason you cannot reduce the noise level to 90 dB, then the Factory Rules provide to curtail the exposure period—half time for each 5 dB rise. For example, if it is 95 dB, only 4 hours of work in that particular area are allowed, and if it is 100 dB, only 2 hours of exposure are permitted. This is just on paper, and I have not heard if it is enforced even at a single unit. If anyone knows, please let us know.

Gujarat Factory Rule 102: High Noise Schedule

The Gujarat Factory Rule 102 has a schedule for High Noise, according to which once a year, each worker exposed to high noise should undergo an audiometry test. Many factories carry it out but do not provide the report to the workers or explain the content of the report to the worker. The Factories Act also provides to notify cases of Noise-induced hearing loss to the concerned authority, which again is not being done. We have helped several workers in power plants, textiles, chemicals, and engineering to get diagnosed and claim compensation for the damage under the ESI Act.

Regards

Dear PTRC, Happy to see your contribution after a long time.

Dear Murdhar, PTRC has explained it correctly. For every 5 dBA increase in noise level, the exposure time of the workmen should be reduced by half. If you focus on complying with legal laws, you should be able to find solutions.

Regarding Air Compressors

The noisy compressors that were usually reciprocating types have now been replaced by screw compressors. They also come with acoustic enclosures and are energy-efficient. Many companies have replaced old compressors with screw types and enjoyed payback within less than 12 months, along with a reduction in noise levels.

Thanks & Regards,
Sudhir

Ok, Mr. Sudhir, what about heavy DG sets (>2 MW engines)? The noise level cannot be reduced, and the operators or the working personnel in and around the machines have to wear personal protective equipment. There is no other choice.

Dear All, so far, great discussion... Thank you all for participating and providing valuable inputs.

Survey Equipment Inquiry

Dear Mr. Bipin Gautam, please let me know how you are conducting this walkabout survey. What equipment are you using for this survey?

Recently, I saw a portable noise monitoring device with the marketing executive of M/s. Honeywell. Similar to how we conduct personal sampling to determine the average dust exposure during an 8-hour workday for individuals in dusty environments, this equipment can be utilized. The employee simply attaches this small, convenient device to their pocket or belt and carries on with their 8-hour work shift, including lunch break. Afterward, the results are noted to assess the exposure over the entire work duration and plan preventive measures accordingly.

Traditional vs. New Approach

Please share your approach for this survey. In the traditional method, we typically monitor exposure from a distance of 5 to 10 meters momentarily from the noise source and record the findings. However, measuring exposure over the full 8-hour period seems more effective than the traditional approach.

I look forward to hearing comments from all members regarding this matter.

Thank you.

Dear Dipil,

You are correct. The workplace monitoring is done for TWA (Time Weighted Average) for 8 hours. This is true for exposures to dust, as in your case, and also becomes critical for exposures to various chemicals. Such monitoring is called workplace monitoring as per the Factories Act Second Schedule.

Understanding STEL (Short Term Exposure Limit)

There is another term called STEL (Short Term Exposure Limit) which is for 15 minutes. The STEL limits are slightly higher than the TWA limits. The exposure of the operator to TWA or STEL is decided by what they do.

To explain this situation, the following example would be useful:

If we take a case of pollution at road signals, the traffic police are exposed for 8 hours as they do duty all the time in a polluted area. However, a vehicle passing through that signal point, the driver is exposed only for 15 minutes. Hence, for the driver, STEL would be applicable.

Noise Monitoring Example

In the above example of noise monitoring, according to my view, as long as the process does not change, the noise level may not change. Moreover, the noise is usually measured at a 1-meter distance from the source. This should be okay.

I request the members having exposure to continuous process plants and cases of variations in noise levels to share their experiences.

Thanks & Regards,

Sudhir

Sudhir, you are confusing the discussion. Clearly, the discussion here is only regarding the noise survey. In the 2nd Schedule of the Factories Act, 90 dB is the TLV (TWA) for noise. No STEL has been prescribed for noise in the schedule.

Nice to see your active participation in the discussion under this forum title after a long time. Can you tell me the ideal way of monitoring noise? How should it be done? What should be the measuring equipment to be used?

Regards

Thank you for your reply. When it comes to dust, I believe most organizations conduct personal monitoring for 8 hours. However, in the case of noise, people are not monitoring for the same duration. They may simply go to a specific location with a sound level meter, take measurements, and return.

Continuous Monitoring for Noise

In the example you mentioned regarding the Traffic Police, I suggest opting for continuous monitoring (TWA for 8 Hours) rather than short-term checks. Traffic conditions can vary, with more trucks or two-wheelers at different times, leading to fluctuating sound levels.

You also mentioned measuring the distance from the noise source at one meter. I recall reading that measurements should be taken at distances of 5 or 10 meters from the source of noise. I am unsure if this information is accurate. Is this distance specified in any regulations? How can we ensure accurate noise monitoring?

Dear Dipil, you are correct. Workplace monitoring is typically conducted for TWA (Time Weighted Average) over 8 hours. This monitoring is crucial for exposures to dust, chemicals, and other substances, as outlined in the Factories Act Second Schedule.

Understanding STEL and TWA

Another important term to consider is STEL (Short-Term Exposure Limit), which applies to 15-minute intervals. STEL limits are slightly higher than TWA limits. The exposure level (TWA or STEL) depends on the individual's tasks.

For instance, in a scenario involving road pollution, a traffic police officer is exposed for 8 hours due to continuous duty in a polluted area. In contrast, a driver passing through the same area is exposed for only 15 minutes, making STEL more relevant for the driver.

Regarding noise monitoring, as long as the process remains constant, the noise level is unlikely to change significantly. Typically, noise levels are measured at a distance of 1 meter from the source, which is generally acceptable.

I encourage members with experience in continuous process plants and noise level variations to share their insights.

Thanks & Regards,
Sudhir

Personal dosimeter is probably the best idea. Equipment has to be of a standard brand (I have no idea, but that can be looked for. I have simple equipment donated to us by our US friend). What is probably more important is Calibration. At least every 6 months, it should be calibrated, and if you are not using it regularly, then before every use, it should be calibrated.

As for at what distance it should be measured, there is no legal standard available, and we should go by standard practice. I have a lot of literature which I can refer to and come back with a precise reply, but that may need some time. I suppose the ACGIH manual is available on the net, which should be referred.

Thank you for your reply. I will check the ACGIH manual online. Additionally, I will investigate how our environmental cell is conducting these monitoring activities and explore any opportunities for improvement.

Thank you.

Noise and Safety in Industrial Settings

For some time, I was actively participating in the discussion. Finding that there are not many enthusiastic safety professionals, especially youngsters, to discuss safety matters seriously, I kept away from the forum. Safety is a serious matter. It is mostly a matter of life, health, and death. Many topics that are not relevant to safety also come up in the forum, wasting precious time. However, again today by chance, I went through the topics under discussion and found noise being discussed.

The Importance of Noise Management

Noise is a serious issue for industrial hygienists. For the Certified Industrial Hygienist (CIH) Examination conducted by ABIH, noise is one of the seventeen topics. Where a hygienist is not available, safety personnel will have to deal with it.

Our safety people—are they trained to deal with industrial noise? I very much doubt it. We can see there is not much in their curriculum, even in their safety diploma course. A few interested ones probe and collect some information from here and there. Equipped with this information, they manage.

Time is changing. It is essential that industries deal with noise with all its seriousness. In order to convince management about dealing with noise problems, there is only one agency—the Industrial Hygienist/Safety man. It involves a lot of expenditure and effort to have a noise conservation program. Without getting convinced about its seriousness, management will not support it. If a proposal is put up, management will have a lot of queries over it to approve expenditure. Ask yourself! Are you prepared to give convincing replies to these queries?

If not, we will have to study noise and get equipped with sufficient information.

Questions to Consider

Let's start with a few questions:

1. The reference sound pressure is defined as-?
2. At what frequency are A, B, and C weighting scales equal?
3. A type II sound level meter has an accuracy of - dB.
4. Determine the total percent dose for the following noise measurements:
- 1 hour @ 85 dB
- 3 hours @ 95 dB
- 0.5 hours @ 105 dB
5. What is the cumulative resultant noise exposure (approximately) for three machines with the following noise ratings (hint: use the shortcut method)?
- 89 dB
- 92 dB
- 99 dB
6. What is the SPL at 200 feet if the SPL at 20 feet is 103 dB?
7. At 30 feet away, one piece of equipment registers an SPL of 80 dB. A second piece of equipment at 30 feet away registers an SPL of 85 dB. What is the SPL when both units are operating at 30 feet away?
8. An Octave Band analyzer is defined as an instrument to determine
9. Two separate noise sources of 98 dBA and 96 dBA respectively are installed and operated together. What is the combined noise level?
10. Theoretically, the minimum number of sound pressure level measurements needed to determine the sound power output from a non-directional noise source in a free field is -?
11. Which classification of noise is described as: a sharp burst of sound, lasting less than 0.5 seconds, and repeated less than 1 time per second?
12. What is NRR?
13. Why is audiometric testing required?
14. Where are the Noise Dosimeters to be clipped?

Regards,
Kesava Pillai

Your post is an eye-opener. Usually, in an industry, except for the DG Set noise, other workplace noise cases are dealt with using PPEs. Very few organizations follow the practice of job rotation and medical examinations. The need for the above questions is not felt. Your reply is genius, and I request you to post the answers too.

Warm regards,
Sudhir

Replies to the questions would certainly help safety professionals gain knowledge on this important subject. Thank you, Mr. Pillai, for your post and deep interest in the subject. It also speaks of your knowledge on the subject.

Dear Dipil, Thank you for answering most of the questions.

Clarification on Noise Levels

Dear Mr. Pillai, please let us know if these are correct. Secondly, I feel the cumulative resultant noise for 89, 92, and 99 dB levels should be 99 only. I am not sure. Please correct.

Thanks & Regards,
Sudhir

I will try to answer some of the left-out questions of Dipil. I am providing the explanation too so that others can understand the subject, instead of just giving the answers.

Q6. SPL at 200 feet
Ans. 83 dB

Explanation - According to the Inverse Square Law, which states that the sound level will drop by a factor of 4 at each doubling distance from the source. It also means that the sound level will drop by -20 dB at each ten times distance. (Need your feedback on the same)

Q9. Calculation Formula
There is a formula for calculation. I was able to retrieve this from my notes. But I am unable to input the formula here as a formula. I hope you can understand and guide us accordingly:

Lc = L1 + 10 Log (10 power ((L2 - L1)/10) + 1)

I am unable to evaluate the problem now as I do not have a scientific calculator. Assumption - the answer would be 99 - 100 dB.

Q11. Classification of Noise
The classification is Impulsive noise.

Explanation - Impulsive Noise consists of one or more bursts of sound energy, each having a duration less than 1 sec. (They are of two types - explosively generated and impact generated). I think this would be impact generated of Impulsive noise classification.

Q12. Additional Information on NRR
In addition to Dipil's answer, NRR is the amount of sound reduction that hearing protection can provide. The higher the NRR dB rating, the greater the amount of noise reduction.

I am unable to answer Q10.

Thank you for the intimation and for inviting me to take part in this discussion. However, I have not gone through the complete discussion but have directly answered the questions from your link. If the answers are already provided, this would be additional information for all.

Regards.

Dear friends,

In safety, any question should never be answered with phrases like "I think," "I feel," and the like. If a safety officer's answer is "I think this is the safe way," it is not acceptable. They should say "yes" or "no," or otherwise state "this is safe" or "this is not safe" firmly. Listing references may help, but who is going to refer and learn all those? Most prefer ready-made answers.

This was the original post:

"To assess the potential risk from noise, I am planning to conduct a walkabout survey to identify possible activities/areas of sufficient noise exposures to determine if additional monitoring is necessary."

"Do you have any idea with this regard?"

Now friends, think—if you posed this question, what would you expect to receive?

Remember! The plan is to conduct a walkabout survey only.

Why the Initiative?

- Experienced noise problems in a few areas.
- Received complaints from employees or certain areas about noise problems.
- Recommendations from audit reports, statutory authorities, etc.

Consider two different scenarios:

1. I have no sound level meter, and if necessary, I will have to advise purchasing one.
2. I have a sound level meter.

Start with the First Scenario:

Decide how you will go about the survey.

Step 1: Get a master plan for all the activities.
Step 2: Identify "no problem" areas and mark them (specify a color, preferably green, and mark).
Step 3: Decide to use different colors for very serious, serious, and borderline case areas.
Step 4: Go to every nook and corner where you experience a noise problem and try to talk to employees, keeping them at arm's length. Wherever you feel you have to raise your voice to be heard, decide yourself the situation as very serious, serious, or borderline case and mark on the plan.

Consolidate the findings and make a recommendation accordingly for a systematic noise survey.

Start with the Second Scenario:

Follow steps 1 and 2 as in the first scenario.

Step 3: Use the SLM and record the readings. Readings should be taken at random near the source, at various distances where employees will be working. Mark the distances and the readings in the plan. As far as possible, readings should be taken at peak hours only.

Consolidate the findings and make a recommendation accordingly for a systematic noise survey.

Doing a systematic noise survey is not just about taking readings. It must be done by an audiometric technician. They require layout drawings marked with each machine/plant. They also use SLM and frequency analyzers to conduct the survey. There is more to it.

Regards,
Kesava Pillai

I have tried to answer the questions - please correct if wrong. Special thanks to Dilip for bringing this thread to my notice.

Answers as under:

1. The reference sound pressure is defined as:
- 20 µPa (sound pressure in air is 20 µPa RMS, which is usually considered the threshold of human hearing at 1 kHz).

2. At what frequency are A, B, and C weighting scales equal?
- 1000 Hz

3. A type II sound level meter has an accuracy of:
- +/-1 dB (new standard IEC 61672)

4. Determine the total percent dose for the following noise measurements:
- 142% (D = 100 (C(1)/T(1) + C(2)/T(2) + ... + C(n)/T(n)))

5. What is the cumulative resultant noise exposure (approximately) for three machines with the following noise ratings (hint: use the shortcut method)?
- 99 dB (When the difference between two noise levels is 10 dB(A) or more, the amount to be added to the higher noise level is zero. In such cases, no adjustment factor is needed because adding in the contribution of the lower in the total noise level makes no perceptible difference in what people can hear or measure.)

6. What is the SPL at 200 feet if the SPL at 20 feet is 103 dB?
- 83 dB (SPL2 = SPL1 + 20 × log (d1 / d2); SPL2 = 103 + 20 × log (20/200); SPL2 = 83 dB)

7. At 30 feet away one piece of equipment registers an SPL of 80 dB. A second piece of equipment at 30 feet away registers an SPL of 85 dB. What is the SPL when both units are operating at 30 feet away?
- 86 dB (Numerical difference between two noise levels & Addition of 01 dB- Amount to be added to the higher of the two noise levels)

8. An Octave Band analyzer is defined as an instrument to determine:
- the frequency distribution of sound energy

9. Two separate noise sources of 98 dBA and 96 dBA respectively are installed and operated together. What is the combined noise level?
- 100 dBA (Numerical difference between two noise levels & Addition of 02 dB- Amount to be added to the higher of the two noise levels)

10. Theoretically, the minimum number of sound pressure level measurements needed to determine the sound power output from a non-directional noise source in a free field is:
- This one I don't know

11. Which classification of noise is described as: sharp burst of sound, lasting less than 0.5 seconds, and repeated less than 1 time per second?
- Impact (Impulse or impact noise is a very short burst of loud noise which lasts for less than one second. Gunfire or the noise produced by punch presses are examples of such noise)

12. What is NRR?
- The noise reduction rating of hearing protection.

13. Why is audiometric testing required?
- To test for any hearing loss during your employment.

14. Where are the Noise Dosimeters to be clipped?
- We clip it on the collar of the shirt.

Regards.

Dear Sir, thanks for participating in the thread and coming up with your answers.

Feedback Request

Dear Kesava Sir, I expect to get your feedback with a source on the web where we can get all the desired results related to occupational noise.

Regards.

Dear Keshav, my heartfelt gratitude for such an excellent post. Regarding Q-10, I wish to have a bit more insight—if you can help. Frankly, I did not and am not able to catch the question—even when the answer is 1. Is it related to SPL monitoring in congested plants?

Again, many thanks for the excellent post—keep posting. I am going to post these questions to our corporate HSE too.

Regards

In measuring sound, we divide the field as follows:

Free Fields

• Sound radiates from a point source spherically.
• The power in the sound source is distributed across the surface of the sphere.
• No contribution to the measured field from reflections.

Reverberant Field

• Enclosed or partially enclosed space.
• Sound is reflected repeatedly.

Near Field

• Less than one source distance from the source.
• Highly variable change in SPL with distance.

Far Field

• Several source distances away.
• Predictable sound behavior with distance.
• Source acts as a point source.

Since in a free field there is no contribution to the measured field from reflections, we need only one reading. Hope the information is useful.

Regards,
Kesava Pillai