The document discusses methods for selecting suitable hearing protection and estimating noise exposure levels when wearing ear defenders. It provides data on the attenuation performance of sample ear defenders and uses this to calculate estimated exposure levels using octave band, HML, and SNR methods. The octave band method involves subtracting the assumed protection level from noise levels in each frequency band. The estimated level is then 69dB(A). The HML and SNR methods estimate levels of 71dB(A) and 70dB(A) respectively. Key factors to consider for effective hearing protection include compatibility with the user, job, other PPE, as well as fitting, maintenance and training. The aim is to reduce noise levels at the ear to between 60-80

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