Dipil
Safety Consultant
Raghuvaran Chakkaravarthy
Environmental, Health And Safety
Svsrana
Hr Head With Pmi
Neeraj4all
Lead - Ims
Bipin Gautam
Hseq Manager
Asudhir17
Agm Ehs And Project Management
Kesava Pillai
Occupational Safety & Health
Kvsundaram
Safety & Production
PTRC
Working With Ngo
+2 Others

Thread Started by #Bipin Gautam

Dear All,
To assess the potential risk from noise, I am planning to conduct a walkabout survey to identify possible activities/areas of significant noise exposures and to determine if additional monitoring is necessary.
Do you have any idea with this regards.
Kind Regards,
Bipin Gautam
4th June 2012 From Oman
Dear Bipin,
Noise Hazard it's one of the big concern and big challenge in our work place international level. Just follow the below links which was more stringent OSHA was given a brief on below links how to conduct noise survey's? Who should be conduct survey's? etc..,,,
Noise and Hearing Conservation Technical Manual Chapter: Section III: How do I evaluate noise exposure? <link updated to site home>
Noise and Hearing Conservation Technical Manual Chapter: Evaluation (App III:A-3) <link updated to site home>
<link outdated-removed> ( Search On Cite | Search On Google )
Note: Attached the OSHA noise survey & analysis report AND Measurement of workplace noise pdf files for your reference.
Hope its helps. keep on touch. . .
4th June 2012 From United States, Fpo

Attached Files
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File Type: pdf Noise Surveys Data Analysis.pdf (283.3 KB, 380 views)
File Type: pdf Noise - Measurement of Workplace Noise.pdf (1.44 MB, 389 views)

Dear Bipin,
In addition to what Mr. Raghu has explained, you may refer the Factories Act.
It is a good idea to conduct a walk through survey.
It will drive your attention to noisy areas.
Factories Act has considered 90 dBA noise level and TLV limit for 8 hours exposure.
Once you identify potential for improvement, you have to control the noise at its source, by engineering controls which include ...
1. Acoustic Enclosures
2. Good Maintenance of machines
The another way is administrative controls where reducing the noise at its source is not possible.
1. Isolation: Isolate the noisy area
2. Job rotation
You may conduct audiometry tests of the employees with increased frequency and compare results with the last tests.
If in case you need any more inputs pl let me know.
Thanks & Regards,
Sudhir
4th June 2012 From India, Nasik
Dear Sudhir,
In addition to the points you have mentioned above, where the noisy area cannot be avoided, like working in quarries, or surrounded by noisy machines like big compressors, DG sets, it is safe to use personnel protective equipments, like ear muffs, ear plugs etc for the personnels working those areas.
Thanks
5th June 2012 From India, Mumbai
Dear Murdhar,
DG set is suposed to have aucoustic enclosure.
If both the compressor or DG set are in one room, you may think of acoustic room for both of them together.
PPEs are to be used as a last defence.
You should not rely on only PPEs
Thanks & Regards,
Sudhir
5th June 2012 From India, Nasik
Dear Sudhir,
Acoustic enclosure for noisy machines is only for the noise preventing to external persons and not to the persons who are working near the machines. Operators, Maintenance technicians who have to visit the machines often to check their normal running cannot avoid the noise generated by these. Hence, it is imperative, that they have to use personnel protective equipments like ear muffs, ear plugs etc.
Generally during the design stage of specifications of these machines itself, noise permissible has been indicated to be less than 90 DB (ninety decibels). But due to aging factors, and due to some faulty design or improper balancing etc (there are so many factors to contribut to high level of noise than the prescribed ones) these high noise or vibrations occurs. Its the responsibility of operators, maintenance technicians to identify the cause and eliminate them.
Hope this clarifies .
Thanks.
5th June 2012 From India, Mumbai
Sudhir is right that noise level has to be controlled at source. If for any reason you can not reduce noise level to 90dB, then the Factory Rules provide to curtail the exposure period - half time for each 5 dB rise i.e. if it is 95 dB, only 4 hr work in that para and if it is 100 dB, 2 hr exposure is allowed.This is just on paper and I have not heard if it is enforced even at a single unit.If anyone knows pl. let us know. The Guj.Factory Rule 102 has a schedule for High Noise according to which once in a year each worker exposed to high noise should undergo audiometry test. Many factories carryout it but do not part the report to the workers OR do not explain the content of the report to the worker. The F.Act also provide 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 plant, textile, chemical, engineering to get diagnosed and claim compensation for the damage under ESI Act
6th June 2012 From India, Coimbatore
Dear PTRC,
Happy to see your contribution after a long time.
Dear Murdhar,
PTRC has explained in correctway.
For every 5 dBA increase in noise level the exposure time of thw wrokmen should reduced by half.
If you have focus to comply the legal laws, you should be able to find ways out.
As regards to air compressors, the noisy compressors usually were reciprocating type have now been replaced by screw compressors. The too come with acoustic enclosures.
These are energy efficient as well.
Many companies have replaced old compressors with screw type and enjoyed pay back within less than 12 months with reduction in noise levels.
Thanks & Regards,
Sudhir
6th June 2012 From India, Nasik
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 personnel protective equipments. There is no other choice
6th June 2012 From India, Mumbai
Dear All

So far great discussion... Thanks all for participating and giving great inputs...

Dear Mr. Bipin Gautam

Please let me know how you conducting this walkabout survey... What is the equipment you are using for conducting this survey...

Recently I have seen one portable noise monitoring equipment with the marketing executive of M/s. Honeywell... Like we doing personal sampling for knowing the average exposure of dust during the 8 hours work for a person working in dusty environment this equipment works... The employee working has to attach this small handy equipment in his pocket or belt and allow the employee to do his 8 hours work... Which may includes the one hour lunch time... Then note the result... See what is the exposure for 8 hours... Then accordingly planned for preventive actions...

However do let me know how you plan to do this survey... I think in traditional way we are just monitoring the exposure from a distance of 5 & 10 meter momentarily from source of noise and noting down the results... I think measuring the exposure for 8 hours is always better than this traditional way...

Expecting comments from all the members on this aspect...
7th June 2012 From India
Dear Dipil,

You are correct.

The work place monitoring is done for TWA (Time weighted Average) for 8 Hours.

This is true for exposures of dust as in your case also becomes critical for exposures to various chemicals. Such monitoring is called workplace monitoring as per Factories Act Second Schedule.

There is another term called STEL (Short Term Exposure Limit) which is for 15 minutes. The STEL limits are slightly more than TWA limits.

The exposure of the operator is for TWA or for STEL is decided by what he does.

To explain this situation the following example would be useful.

If we take a case of pollution on road signals, the traffic police is exposed for 8 hours as he does duty all the time in polluted area, however a vehicle passing through that signal point the driver is exposed only for 15 minutes, hence here for the driver STEL would be applicable.

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. More over the noise is usually measured at 1 meter distance from the source. This should be OK.

Request the members having exposure to continuous process plants and cases of variations in noise levels to share their experience.

Thanks & Regards,

Sudhir
7th June 2012 From India, Nasik
@ Sudhir..You are confusing the discussion. Clearly here the discussion is only regarding noise survey. In 2nd Schedule of the F.Act 90 dB is TLV (TWA) for noise. No STEL has been prescribed for noise in the Schedule
8th June 2012 From India, Coimbatore
Dear Sir
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 it should be done? What should be the measuring equipment to be used?

8th June 2012 From India
Dear Sir
Thanks for your reply.
In the case of dust I think personal monitoring is of 8 hours is doing by most of the organizations... But when comes to noise I people are not doing this s hours monitoring... May be going to a particular location with the sound level meter and measuring and coming back...
In the example you bring about the Traffic Police man, I would say we should go for continuous monitoring (TWA for 8 Hours) than checking it for short term... Cause traffic may be different time to time... May be more trucks plying than cars or two wheelers, hence sound level also fluctuating one...
Then you have mentioned about the measuring distance from source is one meter... I read somewhere it should be measured at a distance of 5 & 10 meter from the source of noise... I don't know whether it is authentic or not? Is this distance is mentioned anywhere in any act?? How we should do perfect monitoring of noise???

8th June 2012 From India
@ Dipil
Personal dosimeter is probably best idea. Equipment has to be of 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 lot of literature which I can refer and come back with precise reply but that may need some time. I suppose ACGIH manual is available on net which should be referred.
10th June 2012 From India, Coimbatore
Dear Sir
Thanks for your reply..
I will check for ACGIH manual online...
I will also check how our environment cell conducting these monitoring and will see is there any opportunity for improvement...
10th June 2012 From India
hi murdhar..
there will be places wherein PPE are in use currently..
however what we need to remember is these are actually business opportunity areas.
there are firms investing in R&D bringing out newer technologies/ devices/ even robotics ...
i have worked with leading conglomerate in middle east..
one of our division was glass manufacturing...
we switched to automatic probes/ climate controller enclosure even though it was a very expensive proposition.
10th June 2012 From India, Delhi
Dear Friends,

For some time I was actively participating in the discussion. Finding there is not many enthusiastic safety professional 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 a topic which is no way relevant to safety also comes up in the forum wasting precious time. However again today by chance I went through the topics under discussion and found NOISE being discussed.

Noise is a serious issue for industrial hygienist. For Certified Industrial Hygienist (CIH) Examination conducted by ABIH, of seventeen topics noise is one. Where 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. We can see there is not much in their curriculum for even in their safety diploma course. 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 managements about dealing with noise problems there is only one agency - the Industrial Hygienist/Safety man. It involves 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 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 about noise and get equipped with sufficient information.

Lets us 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 short cut method)?

1. 89 dB

2. 92 dB

3. 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 a SPL of 80 dB. A second piece of equipment at 30 feet away registers a 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 non-directional noise source in a free field is -?

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?

12. What is NRR?

13. Why is audiometric testing required?

14. Where are the Noise Dosimeters to be clipped?

Regards,

Kesava Pillai
12th June 2012 From India, Kollam
Dear Sir,
Your post is eye opener.
Usually in an industry except for the DG Set noise, other work place noise cases are delt with PPEs.
A very few organisations follow the practice of Job Rotation, Medical Examination.
The need of above questions is not felt.
Your reply is genious and request to post the answers too.
Warm regards,
Sudhir
12th June 2012 From India, Nasik
Good Morning Mr.Kesav pillai,

Nice to see you after very long time Just take a look on below links we didn't get answer but it’s very important/ interesting topic to our EHS professionals - EHS Newsletter, Safety Campaign, and Gas cylinder. Take a look on it.

https://www.citehr.com/411964-ehs-news-letter.html

https://www.citehr.com/412356-safety-campaign.html

https://www.citehr.com/410730-gas-cylinder-safety.html

Let's go to topic Sir, Most of topic we had a very serious discussion in our forum and got great solution on our forum. I agreed your one of the best EHS profession ever seen then u shared tons of technical matters with us on lot of threads.

No one ready to share his experience specially seniors (I’m not mean all seniors) with youngsters. I am preparing for CSM from NASP and CSP from BCSP. I asked to one of my senior who holding the CSP provide me the materials because it’s too expansive Volume – I and Volume – II costs 2000 $ + but he simply said he don’t have materials (even i asked him I’ll pay for it). Here in our forum one of our member said to me will send the document/file; since last August, 2011 still he saying will send you may it takes him only 10 min to post the courier but?

No one not ready to share his knowledge specially who having extraordinary data’s with him. You can upload one file in our forum within a week at least more than 500 people downloading the file but not more than 10 people putting his comment then what about 490 persons?

I’m a certified OSHA 311 fall protection certificate holder but I know still I’m not able to answer some technical questions it’s not mean doesn’t know about fall protection still I’m learning please help your juniors like us; share your valuable experience with us, educate and guide us to improve our skills & qualification to save our precious human lives as a EHS professional.

Again, please whenever you get time share your view ask some questions on various topic participate on our thread it will help us to improve our skill on EHS side.

Keep on touch.

Note; We have a CEO visit in our camp really very busy as soon as getting time will try to answer your questions.
13th June 2012 From United States, Fpo
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
13th June 2012 From India, Coimbatore
Dear Kesava Pillai Sir

Hope you are doing well...

It's really surprising to see you back into the forum and thanks a lot for shows your concern openly... I have been regular here and I am very sure that the things been changed now... It's not that only few members are participating into the forum discussions nowadays... More peoples are trying to give their best to the forum... I am very sure if support from seniors like you is there with us us through this forum we can surely make it an assured place for getting solutions to the EHS related query... It is really very difficult to get seniors like you those are minded to share their knowledge...

When comes to my professional life I got more responsibilities with a great supporting platform for implementation of better ideas for ensuring a safe working environment... If support from seniors like you with me I can do things in a better manner... Hope to get your continuous support like earlier...

Most of the questions raised by you is new to me... However surely will try to answer after referring various sources including internet... I will get back to you soon, may be by today evening with my trail or maximum by tomorrow...

My humble request you to try to be regular here with your inputs...
14th June 2012 From India
Dear Dipil,
Thank you for answering most of the questions.
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. Pl correct.
Thanks & Regards,
Sudhir
16th June 2012 From India, Nasik
Dear Kesava sir,

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, inspite of giving the answers.

Q6. SPL at 200 feet - Ans. 83 dB

Explanation - According to 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 -20dB at each ten times distance.

(Need your feed back on the same)

Q9. There is a formula for calculation. I was able to recover this from my notes. But I am unable to feed the same formula here as a formula. I hope you can understand & 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 now.

Assumption - the answer would be 99 - 100 dB.

Q 11. 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 - explosive generated & impact generated). I think this would be Impact generated of Impulsive noise classification.

Q 12. In addition to Dipil's answer, NRR is the amount of sound reduction that a hearing protection can provide. Higher the NRR dB rating means greater amount of noise reduction.

I am unable to answer the Q 10.

Dear Dipil,

Thank you for the intimation & requesting me to take part in this discussion.

However, I have not gone through the complete discussion, but directly answered the questions from your link. If the answers are already answered, this would be an additional information for all.
16th June 2012 From India, Delhi
Dear Mr. KVS, Thanks a lot for for your post. It is good to know the science associated with an issue. You have explained scientific terms with mathematical formulae. Thanks again. regards, Sudhir
16th June 2012 From India, Nasik
Dear friends,

In safety, for any question answer should never be attached with phrases like ‘I think”, “I feel” and the like. If an answer from a safety officer is “I think this is the safe way” it is not acceptable. He should have to say “yes” or “no” or otherwise “this is safe” or “this is not safe” firmly. Again 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 walk about 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 you expect to receive?

Remember! Plan is to conduct a walk about survey only.

Why the initiative?

Experienced noise problems at few areas.

Received complaints from employees or certain areas about noise problems.

Recommendations from Audit report, Statutory authorities etc.

Consider two different scenarios-

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

2. Identify “no problem” areas and mark (Specify a color preferably green and mark).

3. Decide to use different colors for very serious, serious and border case areas.

4. Go to every nook and corner where you experience a noise problem and try to talk to employees keeping them at arms length. Where ever you feel you have to raise your voice to be heard decide yourself the situation as very serious, serious, or border 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 reading. 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 taking readings. It must be done by an audiometric technician. He requires lay out drawings marked with each machine/plant.

He also uses SLM and frequency analyzer to conduct the survey. There is more to it.

Regards,

Kesava Pillai
16th June 2012 From India, Kollam
Dear friends,

To make it simple the sample questions are made into multiple choices and reproduced. For Certified Industrial Hygienist examination this is exactly how questions are given. (Except No.14). You may try it now and later I will post the correct answers. After all these; we can go deeper into the subject if someone is really interested.

SAMPLE QUESTIONS

Choose the correct answer.

1. The reference sound pressure is defined as:

• O0.00002N/m²

• 20 ΅a

• 2΅N/m²

• Both A and B

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

• 500 Hz

• 1000 Hz

• 2000 Hz

• 4000 Hz

3. A type II sound level meter has an accuracy of

• +/-1 db

• +/- 2 dB

• +/- 3 dB

• +/- 6 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

3.5 hours @ 80 dB

• 86%

• 100%

• 142%

• 350%

5. What is the cumulative resultant noise exposure (approximately) for three machines with the following noise ratings (hint: use the short cut method)?

1. 89 dB

2. 92 dB

3. 99 dB

• 98 dB

• 99 dB

• 100 dB

• 101 dB

6. What is the SPL at 200 feet if the SPL at 20 feet is 103 dB?

• 83 dB

• 76 dB

• 89 dB

• 80 dB

7. At 30 feet away one piece of equipment registers a SPL of 80 dB. A second piece of equipment at 30 feet away registers a SPL of 85 dB. What is the SPL when both units are operating at 30 feet away?

• 83 dB

• 84 dB

• 85 dB

• 86 dB

8. An Octave Band analyzer is defined as an instrument to determine

• a sound level within a fraction of a decibel

• peak-to-peak SPL's

• SPL in A, B and C weighted network

• 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?

a. 99 dBA

b. 100 dBA

c. 101 dBA

d. 194 dBA

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

• one

• two

• four

• eight

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?

• Continuous

• Intermittent

• Impact

• Direct

12. What is NRR?

• The noise level of rifles.

• The noise rating of any loud machinery.

• The noise reduction rating of hearing protection.

• A measure of how well earplugs work.

13. Why is audiometric testing required?

• To make sure you haven’t gone deaf.

• To test for any hearing loss during your employment.

• To test the noise of machinery.

• To see how well you remember noise training material.

14. Where are the Noise Dosimeters to be clipped?

Regards,

Kesava Pillai
17th June 2012 From India, Kollam
Dear Kesava Sir
Thanks for your detailed two posting... Really sound and something different than what been expected... As always you just don't want to do spoon feeding...
Really by referring various websites and reading more on the topic will help to improve knowledge on the topic...
Will come back to you soon with right answers...
Thanks and keep on sharing your expertise with us...
17th June 2012 From India
Dear Keshav

I have tried to answer the questions - please correct if wrong.

Special thanks to Dilip for bringing this tread to my notice.

Answers as under:

1. The reference sound pressure is defined as:

• 20 ΅a (sound pressure in air is 20 ΅Pa 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 short cut 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 a SPL of 80 dB. A second piece of equipment at 30 feet away registers a 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?

b. 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. Gun fire 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 collar of shirt
27th June 2012 From India, Mumbai
WOW! Raghu, You again rocked dear. Thanks for info. Dear Bipin, I’ll get back to you soon with some input. Regards, Inderjeet Singh, "Born to lead."
27th June 2012 From India, Rajsamand
Dear Sir
Thanks for participation into the thread and come up with your answers...
Dear Kesava Sir
Expect to get your feedback with a source on web where we can get all the desired results related to occupational noise...

28th June 2012 From India
Dear Neeraj

Thanks you, all the answers you gave are right.

One that is missing from yours can be noted from the answers given below.

SAMPLE QUESTIONS

1. The reference sound pressure is defined as:

• O0.00002N/m²

• 20 ΅a

• Both A and B

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

4. Determine the total percent dose for the following noise measurements:

1 hour @ 85 dB

3 hours @ 95 dB

0.5 hours @ 105 dB

3.5 hours @ 80 dB

• 142%

5. What is the cumulative resultant noise exposure (approximately) for three machines with the following noise ratings (hint: use the short cut method)?

1. 89 dB

2. 92 dB

3. 99 dB

• 100 dB

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 a SPL of 80 dB. A second piece of equipment at 30 feet away registers a SPL of 85 dB. What is the SPL when both units are operating at 30 feet away?

• 86 dB

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?

b. 100 dBA

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

• one

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

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?

Close to the ear (In to the collar)



Regards,

Kesava Pillai
28th June 2012 From India, Kollam
Dear Keshav
My hearful 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 excellent post - keep posting. I am going to post these question to our corporate HSE too.
Regards
28th June 2012 From India, Mumbai
Dear Neeraj
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 measured field from reflections.
Reverberant field :
• Enclosed or partially enclosed space
• Sound reflected repeatedly
Near Field :
• Less than one source distance from source
• Highly variable change in SPL with distance.
Far Field:
• Several source distance away
• Predictable sound behavior with distance
• Source act as a point source.
Since in a free field there is no contribution to measured field from reflections we need only one reading.
Hope the information is useful
Regards,
Kesava Pillai
28th June 2012 From India, Kollam
Dear Keshav
My bow with gratitude.
Now I am little learned.... Jokes apart but really thanks.
I was really confused and you have cleared the doubt.
My Thanks to Dilip too who took me to this valuable thread.
Please keep posting.
Regards
29th June 2012 From India, Mumbai
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