Occupational Noise Survey - Pdf Download - CiteHR
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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
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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...
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
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.
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
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
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
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...
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
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."

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