Selection of ear defenders

Mike Slater

First, consider technical performance

To do this, you’ll need information from the supplier of the proposed ear defenders

Supplier’s InformationPeltor Optime 1Octave (Hz) 125 250 500 1000 2000 4000 8000Mean 11.6 18.7 22.5 32.9 33.6 36.1 35.8attenuation(dB)Standard 4.3 3.6 2.5 2.7 3.4 3.0 3.8deviation (dB)Assumed 7.3 15.1 25.0 30.2 30.2 33.1 32.0protection(dB) H = 32 M = 25 L = 15 SNR = 27

Supplier’s InformationPeltor Optime 1Octave (Hz) 125 250 500 1000 2000 4000 8000Mean 11.6 18.7 22.5 32.9 33.6 36.1 35.8attenuation(dB)Standard 4.3 3.6 2.5 2.7 3.4 3.0 3.8deviation (dB)Assumed 7.3 15.1 25.0 30.2 30.2 33.1 32.0protection(dB) H = 32 M = 25 L = 15 SNR = 27 Assumed protection = mean attenuation – 1 standard deviation

Supplier’s InformationPeltor Optime 1Octave (Hz) 125 250 500 1000 2000 4000 8000Mean 11.6 18.7 22.5 32.9 33.6 36.1 35.8attenuation(dB)Standard 4.3 3.6 2.5 2.7 3.4 3.0 3.8deviation (dB)Assumed 7.3 15.1 25.0 30.2 30.2 33.1 32.0protection(dB) H = 32 M = 25 L = 15 SNR = 27 Data for simplified methods

There are 3 methods: Using octave band data H M L method SNR method

There are 3 methods: Using octave band data H M L method SNR method Most accurate method

There are 3 methods: Using octave band data H M L method SNR method Simplified methods

Octave Band Method

Octave band method1. Undertake octave band analysis of noise

Octave band method1. Undertake octave band analysis of noise2. Obtain mean attenuation and standard deviation for ear defenders

Octave band method1. Undertake octave band analysis of noise2. Obtain mean attenuation and standard deviation for ear defenders3. Calculate assumed protection in each octave band (mean – 1 standard deviation)

Octave band method1. Undertake octave band analysis of noise2. Obtain mean attenuation and standard deviation for ear defenders3. Calculate assumed protection in each octave band (mean – 1 standard deviation)4. Subtract assumed protection from noise levels in each octave band

Octave band method1. Undertake octave band analysis of noise2. Obtain mean attenuation and standard deviation for ear defenders3. Calculate assumed protection in each octave band (mean – 1 standard deviation)4. Subtract assumed protection from noise levels in each octave band5. Correct for A weighting

Octave band method1. Undertake octave band analysis of noise2. Obtain mean attenuation and standard deviation for ear defenders3. Calculate assumed protection in each octave band (mean – 1 standard deviation)4. Subtract assumed protection from noise levels in each octave band5. Correct for A weighting6. Calculate assumed overall level at ear

Octave band method1. Undertake octave band analysis of noise2. Obtain mean attenuation and standard deviation for ear defenders3. Calculate assumed protection in each octave band (mean – 1 standard deviation)4. Subtract assumed protection from noise levels in each octave band5. Correct for A weighting6. Calculate assumed overall level at ear7. HSE recommend a 4 dB(A) correction is applied to take account of "real world" factors

Octave band centre 125 250 500 1K 2K 4K 8Kfrequency (Hz)Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49Measured levels 86.2 dB(A) 92.8 dB(C) Here’s some data from a noise survey

Octave band centre 125 250 500 1K 2K 4K 8Kfrequency (Hz)Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49Assumed protection 7.3 15.1 25.0 30.2 30.2 33.1 32.0provided by eardefenders (dB)Level at ear wearing eardefenders (dB)A weighting correctionLevel at ear wearing eardefenders (dBA)

Octave band centre 125 250 500 1K 2K 4K 8Kfrequency (Hz)Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49Assumed protection 7.3 15.1 25.0 30.2 30.2 33.1 32.0provided by eardefenders (dB)Level at ear wearing eardefenders (dB)A weighting correctionLevel at ear wearing eardefenders (dBA)Assumed protection is mean attenuation – 1 standard deviation

Octave band centre 125 250 500 1K 2K 4K 8Kfrequency (Hz)Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49Assumed protection 7.3 15.1 25.0 30.2 30.2 33.1 32.0provided by eardefenders (dB)Level at ear wearing ear 76.2 70.3 58.9 51.5 48.2 40.5 17.0defenders (dB)A weighting correctionLevel at ear wearing eardefenders (dBA)Level at ear = measured level – assumed protection

Octave band centre 125 250 500 1K 2K 4K 8Kfrequency (Hz)Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49Assumed protection 7.3 15.1 25.0 30.2 30.2 33.1 32.0provided by eardefenders (dB)Level at ear wearing ear 76.2 70.3 58.9 51.5 48.2 40.5 17.0defenders (dB)A weighting correction -16.1 -8.6 -3.2 0 1.2 1 -1.1Level at ear wearing eardefenders (dBA)These are the specified correction factors for the A weighting

Octave band centre 125 250 500 1K 2K 4K 8Kfrequency (Hz)Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49Assumed protection 7.3 15.1 25.0 30.2 30.2 33.1 32.0provided by eardefenders (dB)Level at ear wearing ear 76.2 70.3 58.9 51.5 48.2 40.5 17.0defenders (dB)A weighting correction -16.1 -8.6 -3.2 0 1.2 1 -1.1Level at ear wearing ear 60.1 61.7 55.7 51.5 49.4 39.5 15.9defenders (dBA)These values represent the A weighted levels at the ear whenthe ear defenders are worn

Octave band centre 125 250 500 1K 2K 4K 8Kfrequency (Hz)Measured level (dB) 83.5 85.4 83.9 81.7 78 73.6 49Assumed protection 7.3 15.1 25.0 30.2 30.2 33.1 32.0provided by eardefenders (dB)Level at ear wearing ear 76.2 70.3 58.9 51.5 48.2 40.5 17.0defenders (dB)A weighting correction -16.1 -8.6 -3.2 0 1.2 1 -1.1Level at ear wearing ear 60.1 61.7 55.7 51.5 49.4 39.5 15.9defenders (dBA)Level at ear wearing ear defenders = 64.9dB(A)Attenuation = 86 – 65= 21 dB(A)

 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)

Simplified Methods HML  high, medium and low SNR  “single number rating”

H M L Method

HML Method1. 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  

HML Method The PNR is subtracted from the A weighted sound pressure level to give the level experienced by the wearer in dB(A)

ExampleMeasured levels 86.2 dB(A) 92.8 dB(C)

ExampleMeasured levels 86.2 dB(A) 92.8 dB(C)Difference is 6.6 dB> 2, so use L and M values

 M  L  PNR  M   LC  LA  2  8  LC = 92.8 dBLA = 86.2dBM = 25L = 15

 25  15  PNR  25   92.6  86.2  2  8   So PNR = 19.5

PNR = 19.5level experienced by the wearer = LA – PNR = 86.2 – 19.5 = 66.7 = 67 dB(A)

 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)

SNR (Single Number Rating) Method

SNR Method The effective A weighted sound pressure level at the ear is given by subtracting the SNR value from LC

SNR MethodLevel at ear = LC – SNR = 92.6 – 27 = 65.6 = 66 dB(A)

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)

Method Level at ear in dB(A)*Octave band 69HML 71SNR 70* Adjusted for “real world” factors

Don’t overprotect

Don’t overprotectAim for a level at the earbetween 60 and 80 dB(A)

HSE Guidance From HSE publication L108 “Controlling noise at work”

We now need to consider otherfactors that will affect how wellthe ear defenders perform

These include compatibility with the: • User • Job • Other PPE

Here are some examples (thereare many others)

1. Compatibility with the user

Compatibility with the userSome people findwearing ear plugsuncomfortable

Compatibility with the userEar muffs can beuncomfortable to wearin hot conditions

Compatibility with the userWith ear muffs,glasses, jewellery andlong hair can interferewith the seals thatkeep noise out

2. Compatibility with the job

Compatibility with the jobWearing ear defenderscan interfere withcommunication .... http://actrav.itcilo.org

Compatibility with the job.... and make it difficultto hear alarms andaudible signals

3. Compatibility with other PPE

Compatibility with other PPEWearing ear muffswith safety helmetspresents particularproblems

Compatibility with other PPEHelmet mountedmuffs can significantlyreduce the attenuationprovided by the muffs

Compatibility with other PPEAnd, of course, safetyglasses can interferewith the seal on earmuffs

Once suitable ear defenders havebeen selected, there are otherimportant considerations toensure that they are effectivewhen they’re being used.

Once suitable ear defenders havebeen selected, there are otherimportant considerations toensure that they are effectivewhen they’re being used.These include:

 Fitting Hearing protection zones Enforcement Care and maintenance Training

http://www.slideshare.net/mikeslatermike@diamondenv.co.ukhttp://diamondenv.wordpress.comTwitter: @diamondenvMike Slater

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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Selection of ear defenders

by Mike Slater on Nov 19, 2011

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Selection of ear defenders Presentation Transcript