Nov. 19, 2011•0 likes•3,183 views

Download to read offline

Report

Health & Medicine

Technology

Mike SlaterFollow

- 1. Mike Slater
- 2. First, consider technical performance
- 3. To do this, you’ll need information from the supplier of the proposed ear defenders
- 4. Supplier’s Information Peltor Optime 1 Octave (Hz) 125 250 500 1000 2000 4000 8000 Mean attenuation (dB) 11.6 18.7 27.5 32.9 33.6 36.1 35.8 Standard deviation (dB) 4.3 3.6 2.5 2.7 3.4 3.0 3.8 Assumed protection (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 H = 32 M = 25 L = 15 SNR = 27
- 5. Supplier’s Information Peltor Optime 1 Octave (Hz) 125 250 500 1000 2000 4000 8000 Mean attenuation (dB) 11.6 18.7 27.5 32.9 33.6 36.1 35.8 Standard deviation (dB) 4.3 3.6 2.5 2.7 3.4 3.0 3.8 Assumed protection (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 H = 32 M = 25 L = 15 SNR = 27 Assumed protection = mean attenuation – 1 standard deviation
- 6. Supplier’s Information Peltor Optime 1 Octave (Hz) 125 250 500 1000 2000 4000 8000 Mean attenuation (dB) 11.6 18.7 27.5 32.9 33.6 36.1 35.8 Standard deviation (dB) 4.3 3.6 2.5 2.7 3.4 3.0 3.8 Assumed protection (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 H = 32 M = 25 L = 15 SNR = 27 Data for simplified methods
- 7. There are 3 methods: Using octave band data H M L method SNR method
- 8. There are 3 methods: Using octave band data H M L method SNR method Most accurate method
- 9. There are 3 methods: Using octave band data H M L method SNR method Simplified methods
- 10. Octave Band Method
- 11. Octave band method 1. Undertake octave band analysis of noise
- 12. Octave band method 1. Undertake octave band analysis of noise 2. Obtain mean attenuation and standard deviation for ear defenders
- 13. Octave band method 1. Undertake octave band analysis of noise 2. Obtain mean attenuation and standard deviation for ear defenders 3. Calculate assumed protection in each octave band (mean – 1 standard deviation)
- 14. Octave band method 1. Undertake octave band analysis of noise 2. Obtain mean attenuation and standard deviation for ear defenders 3. Calculate assumed protection in each octave band (mean – 1 standard deviation) 4. Subtract assumed protection from noise levels in each octave band
- 15. Octave band method 1. Undertake octave band analysis of noise 2. Obtain mean attenuation and standard deviation for ear defenders 3. Calculate assumed protection in each octave band (mean – 1 standard deviation) 4. Subtract assumed protection from noise levels in each octave band 5. Correct for A weighting
- 16. Octave band method 1. Undertake octave band analysis of noise 2. Obtain mean attenuation and standard deviation for ear defenders 3. Calculate assumed protection in each octave band (mean – 1 standard deviation) 4. Subtract assumed protection from noise levels in each octave band 5. Correct for A weighting 6. Calculate assumed overall level at ear
- 17. Octave band method 1. Undertake octave band analysis of noise 2. Obtain mean attenuation and standard deviation for ear defenders 3. Calculate assumed protection in each octave band (mean – 1 standard deviation) 4. Subtract assumed protection from noise levels in each octave band 5. Correct for A weighting 6. Calculate assumed overall level at ear 7. HSE recommend a 4 dB(A) correction is applied to take account of "real world" factors
- 18. Octave band centre frequency (Hz) Measured level (dB) Measured levels 125 83.5 250 85.4 500 83.9 86.2 dB(A) 1K 2K 81.7 4K 78 8K 73.6 92.8 dB(C) Here’s some data from a noise survey 49
- 19. Octave band centre frequency (Hz) 125 250 500 1K 2K 4K 8K Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49 Assumed protection provided by ear defenders (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 Level at ear wearing ear defenders (dB) A weighting correction Level at ear wearing ear defenders (dBA)
- 20. Octave band centre frequency (Hz) 125 250 500 1K 2K 4K 8K Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49 Assumed protection provided by ear defenders (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 Level at ear wearing ear defenders (dB) A weighting correction Level at ear wearing ear defenders (dBA) Assumed protection is mean attenuation – 1 standard deviation
- 21. Octave band centre frequency (Hz) 125 250 500 1K 2K 4K 8K Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49 Assumed protection provided by ear defenders (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 Level at ear wearing ear defenders (dB) 76.2 70.3 58.9 51.5 48.2 40.5 A weighting correction Level at ear wearing ear defenders (dBA) Level at ear = measured level – assumed protection 17.0
- 22. Octave band centre frequency (Hz) 125 250 500 1K 2K 4K 8K Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49 Assumed protection provided by ear defenders (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 Level at ear wearing ear defenders (dB) 76.2 70.3 58.9 51.5 48.2 40.5 17.0 A weighting correction -16.1 -8.6 -3.2 0 1.2 1 -1.1 Level at ear wearing ear defenders (dBA) These are the specified correction factors for the A weighting
- 23. Octave band centre frequency (Hz) 125 250 500 1K 2K 4K 8K Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49 Assumed protection provided by ear defenders (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 Level at ear wearing ear defenders (dB) 76.2 70.3 58.9 51.5 48.2 40.5 17.0 A weighting correction -16.1 -8.6 -3.2 0 1.2 1 -1.1 Level at ear wearing ear defenders (dBA) 60.1 61.7 55.7 51.5 49.4 39.5 15.9 These values represent the A weighted levels at the ear when the ear defenders are worn
- 24. Octave band centre frequency (Hz) 125 250 500 1K 2K 4K 8K Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49 Assumed protection provided by ear defenders (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 Level at ear wearing ear defenders (dB) 76.2 70.3 58.9 51.5 48.2 40.5 17.0 A weighting correction -16.1 -8.6 -3.2 0 1.2 1 -1.1 Level at ear wearing ear defenders (dBA) 60.1 61.7 55.7 51.5 49.4 39.5 15.9 Level at ear wearing ear defenders = 64.9dB(A) Attenuation = 86 – 65= 21 dB(A)
- 25. Calculated level at ear wearing ear defenders = 65 dB(A) Adjust by 4 db(A) to take account of “real world factors” So level at ear is 69 dB(A)
- 26. Simplified Methods HML high, medium and low SNR “single number rating”
- 27. H M L Method
- 28. HML Method 1. Measure level in dB(A) = (LA) 2. Measure level in dB(C) = (LC) 3. If Lc - LA is >2: M L PNR M L C L A 2 8 4. Otherwise: H M PNR M L C L A 2 4
- 29. HML Method The PNR is subtracted from the A weighted sound pressure level to give the level experienced by the wearer in dB(A)
- 30. Example Measured levels 86.2 dB(A) 92.8 dB(C)
- 31. Example Measured levels 86.2 dB(A) 92.8 dB(C) Difference is 6.6 dB > 2, so use L and M values
- 32. Supplier’s Information Peltor Optime 1 Octave (Hz) 125 250 500 1000 2000 4000 8000 Mean attenuation (dB) 11.6 18.7 27.5 32.9 33.6 36.1 35.8 Standard deviation (dB) 4.3 3.6 2.5 2.7 3.4 3.0 3.8 Assumed protection (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 H = 32 M = 25 L = 15 SNR = 27
- 33. M L PNR M LC LA 2 8 LC = 92.8 dB LA = 86.2dB M = 25 L = 15
- 34. 25 15 PNR 25 92.6 86.2 2 8 So PNR = 19.5
- 35. PNR = 19.5 level experienced by the wearer = LA – PNR = 86.2 – 19.5 = 66.7 = 67 dB(A)
- 36. Calculated level at ear wearing ear defenders = 67 dB(A) Adjust by 4 db(A) to take account of “real world factors” So level at ear is 71 dB(A)
- 37. SNR (Single Number Rating) Method
- 38. SNR Method The effective A weighted sound pressure level at the ear is given by subtracting the SNR value from LC
- 39. Supplier’s Information Peltor Optime 1 Octave (Hz) 125 250 500 1000 2000 4000 8000 Mean attenuation (dB) 11.6 18.7 27.5 32.9 33.6 36.1 35.8 Standard deviation (dB) 4.3 3.6 2.5 2.7 3.4 3.0 3.8 Assumed protection (dB) 7.3 15.1 25.0 30.2 30.2 33.1 32.0 H = 32 M = 25 L = 15 SNR = 27
- 40. SNR Method Level at ear = LC – SNR = 92.6 – 27 = 65.6 = 66 dB(A)
- 41. SNR Method Calculated level at ear wearing ear defenders = 66 dB(A) Adjust by 4 db(A) to take account of “real world factors” So level at ear is 70 dB(A)
- 42. Method Octave band HML SNR Level at ear in dB(A)* 69 71 70 * Adjusted for “real world” factors
- 43. Don’t overprotect
- 44. Don’t overprotect Aim for a level at the ear between 60 and 80 dB(A)
- 45. HSE Guidance From HSE publication L108 “Controlling noise at work”
- 46. We now need to consider other factors that will affect how well the ear defenders perform
- 47. These include compatibility with the: • User • Job • Other PPE
- 48. Here are some examples (there are many others)
- 49. 1. Compatibility with the user
- 50. Compatibility with the user Some people find wearing ear plugs uncomfortable
- 51. Compatibility with the user Ear muffs can be uncomfortable to wear in hot conditions
- 52. Compatibility with the user With ear muffs, glasses, jewellery and long hair can interfere with the seals that keep noise out
- 53. 2. Compatibility with the job
- 54. Compatibility with the job Wearing ear defenders can interfere with communication .... http://actrav.itcilo.org
- 55. Compatibility with the job .... and make it difficult to hear alarms and audible signals
- 56. 3. Compatibility with other PPE
- 57. Compatibility with other PPE Wearing ear muffs with safety helmets presents particular problems
- 58. Compatibility with other PPE Helmet mounted muffs can significantly reduce the attenuation provided by the muffs
- 59. Compatibility with other PPE And, of course, safety glasses can interfere with the seal on ear muffs
- 60. Once suitable ear defenders have been selected, there are other important considerations to ensure that they are effective when they’re being used.
- 61. Once suitable ear defenders have been selected, there are other important considerations to ensure that they are effective when they’re being used. These include:
- 62. Fitting Hearing protection zones Enforcement Care and maintenance Training
- 63. http://www.slideshare.net/mikeslater mike@diamondenv.co.uk http://diamondenv.wordpress.com Twitter: @diamondenv Mike Slater
- 64. Mike Slater, Diamond Environmental Ltd. (mike@diamondenv.co.uk) This presentation is distributed under the Creative Commons Attribution-NonCommercial-ShareAlike UK:International Licence