Selection of ear defenders

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Selection of ear defenders

  1. 1. Mike Slater
  2. 2. First, consider technical performance
  3. 3. To do this, you’ll need information from the supplier of the proposed ear defenders
  4. 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. 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. 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. 7. There are 3 methods:  Using octave band data  H M L method  SNR method
  8. 8. There are 3 methods:  Using octave band data  H M L method  SNR method Most accurate method
  9. 9. There are 3 methods:  Using octave band data  H M L method  SNR method Simplified methods
  10. 10. Octave Band Method
  11. 11. Octave band method 1. Undertake octave band analysis of noise
  12. 12. Octave band method 1. Undertake octave band analysis of noise 2. Obtain mean attenuation and standard deviation for ear defenders
  13. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 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. 26. Simplified Methods  HML  high, medium and low  SNR  “single number rating”
  27. 27. H M L Method
  28. 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. 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. 30. Example Measured levels  86.2 dB(A)  92.8 dB(C)
  31. 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. 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. 33.  M  L   PNR  M   LC  LA  2  8   LC = 92.8 dB LA = 86.2dB M = 25 L = 15
  34. 34.  25  15   PNR  25   92.6  86.2  2  8   So PNR = 19.5
  35. 35. PNR = 19.5 level experienced by the wearer = LA – PNR = 86.2 – 19.5 = 66.7 = 67 dB(A)
  36. 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. 37. SNR (Single Number Rating) Method
  38. 38. SNR Method  The effective A weighted sound pressure level at the ear is given by subtracting the SNR value from LC
  39. 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. 40. SNR Method Level at ear = LC – SNR = 92.6 – 27 = 65.6 = 66 dB(A)
  41. 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. 42. Method Octave band HML SNR Level at ear in dB(A)* 69 71 70 * Adjusted for “real world” factors
  43. 43. Don’t overprotect
  44. 44. Don’t overprotect Aim for a level at the ear between 60 and 80 dB(A)
  45. 45. HSE Guidance From HSE publication L108 “Controlling noise at work”
  46. 46. We now need to consider other factors that will affect how well the ear defenders perform
  47. 47. These include compatibility with the: • User • Job • Other PPE
  48. 48. Here are some examples (there are many others)
  49. 49. 1. Compatibility with the user
  50. 50. Compatibility with the user Some people find wearing ear plugs uncomfortable
  51. 51. Compatibility with the user Ear muffs can be uncomfortable to wear in hot conditions
  52. 52. Compatibility with the user With ear muffs, glasses, jewellery and long hair can interfere with the seals that keep noise out
  53. 53. 2. Compatibility with the job
  54. 54. Compatibility with the job Wearing ear defenders can interfere with communication .... http://actrav.itcilo.org
  55. 55. Compatibility with the job .... and make it difficult to hear alarms and audible signals
  56. 56. 3. Compatibility with other PPE
  57. 57. Compatibility with other PPE Wearing ear muffs with safety helmets presents particular problems
  58. 58. Compatibility with other PPE Helmet mounted muffs can significantly reduce the attenuation provided by the muffs
  59. 59. Compatibility with other PPE And, of course, safety glasses can interfere with the seal on ear muffs
  60. 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. 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. 62.  Fitting  Hearing protection zones  Enforcement  Care and maintenance  Training
  63. 63. http://www.slideshare.net/mikeslater mike@diamondenv.co.uk http://diamondenv.wordpress.com Twitter: @diamondenv Mike Slater
  64. 64. Mike Slater, Diamond Environmental Ltd. (mike@diamondenv.co.uk) This presentation is distributed under the Creative Commons Attribution-NonCommercial-ShareAlike UK:International Licence

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