New CSA Noise Standards and Noise Control - OHAO · Hearing Research Laboratory OHAO, Fall PDC Christian Giguère & Flora Nassrallah Toronto - October 23rd, 2013 New CSA Noise Standards

Hearing Research Laboratory

OHAO, Fall PDCChristian Giguère & Flora Nassrallah

Toronto - October 23rd, 2013

New CSA Noise Standardsand Noise Control

CAN/CSA Z107.56Measurement of Occupational Noise Exposure


Table of Contents

• Noise and Hearing Loss• Standard CAN/CSA Z107.56• Communication Headsets• New Procedures in CAN/CSA Z107.56

Specialized Methods Calculation Method Exposure to Music, Radios

• Summary of CAN/CSA Z107.56• Questionnaire• Conclusions


Noise and Hearing Loss

• Second most prevalent self-reported work-related injury.• 22 million American workers are exposed to hazardous

noise (Tak et al., 2009) and 10 million suffer from hearingloss as a result (NIOSH, 2009).

http://www.dangerousdecibels.org/ with permission



Industrial workplace:

• In a sample of over 1.1 million US workers, about 18% had hearing loss (Masterson et al., 2012). Adjusted Prevalence Ratios:

» Mining: 1.65» Wood product manufacturing: 1.65» Construction of buildings: 1.52



Military environment:

• By midlife, 42% of Canadian Force service members show at least a mild hearing loss (>25 dB), and 26% a moderate to severe hearing loss (>40 dB) (Abel, 2005). Twice more affected than by aging alone.

• Some military trades more at risk: Infantry, artillery, flight engineers.



Short-term effects of noise exposure: Temporary hearing loss (TTS) Interference with important hearing tasks Stress, fatigue

Long-term effects of noise exposure: Permanent hearing loss (PTS)

» Hearing sensitivity (audibility)» Supra-threshold deficits (distortion)

Tinnitus Cardiovascular and other diseases


slight

normal

mild

moderate

severe

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Frequency (Hz)

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Age + Noise

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125 250 4000500 1000 2000 8000

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Frequency (Hz)

Hea

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(dB

HL)

80 yrs

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Age

NoisePure-tone audiogram




Speech in noise

(Vaillancourt et al., 2011) (Vaillancourt et al., 2011)

Hearing thresholds are poorly related to speech perception in noise and sound localization.

Localization in quiet


Noise and Hearing LossEffects:• Individual

Quality of life (before and after retirement).• Employer

High cost of rehabilitation services and compensation claims.

WSIB estimated cost of equipment (e.g., hearing aids) can reach 11000$ every four years in Ontario (Ministry of Labour, 2007).

• Workplace Affects speech communication, warning signal

perception, detection and localisation of critical sounds. Decrease in situational awareness, safety, and work

efficiency.


Standard CAN/CSA Z107.56

• Canada has been the first country to issue an occupational noise measurement standard (1986).

• Updated or reaffirmed in 1994, R1999, R2004, 2006, R2011.

• The standards specify methods valid for sources “far” from the ears of workers using: Dosimeter Sound level meter (SLM) Integrated sound level meter

• Since 2007, the exposure limit for 8 hours is 85 dBA in Ontario and 87 dBAfor federal employees (CCOHS, 2011).

CSA Group with permission


Standard CAN/CSA Z107.56

• Revised version of Z107.56 (Publiched in August 2013).

• Sections 4-6 specifies instrumentation and procedures based on sound level meter and noise dosimeters.

• NEW! Section 7 specifies instrumentation and procedures for noise sources “close” to the ears such as headsets.

• NEW! Section 8 specifies procedures to account for use of music players, radios, and other sound reproduction devices.

CSA Group with permission


Communication Headsets

• Exposing 3 million American workers to high levels of noise (OSHA, 1999).

• Increased use of wired and wireless communication headsets in many occupational settings in the past decade.

• Typical uses: call centers, airport ground and control, construction sites, military sites, industrial sites, etc.



Circum-aural

Supra-aural

Intra-concha

Inserts

Monophonic StereophonicDouble Protection Muffs

http://www.davidclark.com/

http://www.plantronics.com/ca/

http://www.sennheiser.ca/live/

http://www.sensear.com/

http://www.sensear.com/

http://www.solutions.3mcanada.ca



1) The measurement problem:

• Noise exposure arises from two sources: External noise passing through headset Internal audio signal (i.e. speech) from headset

• User adjusts volume setting to ensure the proper reception of speech/audio signal above the noise entering the device.

External Noise

Signal Source

Residual Noise



1) The measurement problem (cont.):

• Which equipment should be used to measure sound in the ears?

• Challenges: Sound is produced at or in the ears.

» SLM or noise dosimeter not suitable for in-ear measurements

Measurements must be carried out while the worker is conducting his/her normal duties.

Safety must be maintained.

Noise Dosimeter(B & K)

Sound Level Meter(B & K)



2) The assessment problem:

• How to relate in-ear sound measurements to occupational noise limits?

Speaker

ExternalSound Field

At Eardrum

-10

-5

0

5

10

15

20

25

0.1 1 10Frequence (kHz)

Gai

n (d

B)

Frequency Response of External Ear

Frequency (kHz)


2) The assessment problem (cont.):

• Sound level is measured at the ear but regulatory limit (e.g., 85 dBA) is defined in the sound field.

0

2

4

6

8

10

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12,5 16 20 25

31,5 40 50 63 80 10

012

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0012

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0020

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0031

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0050

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Cor

rect

ion

Fact

or (d

B)

1/3 Octave Band (Hertz)

Correction Factor for Diffuse-Field Equivalency(ISO 11904-2:2004)


Diffuse-Field Level (dBA)

At-Ear Level(dBA)

Speech 85 89.4

Airplane 85 86.6

Crowd 85 91.3

Riveter 85 93.6

Examples of diffuse-field and at-ear measurements


New Procedures in CAN/CSA Z107.56

• Australian/New Zealand Standard (AS/NZS 1269.1:2005).

• From 2007-2011 a Working Group of Technical Committee s304 of the CSA surveyed suitable methods to conduct measurements under communication headsets.

• Version 2013 of the standard offers the use of either: Specialized methods and equipment (Section 7.3.1-

7.3.3) and A simplified calculation method (Section 7.3.4).

• New methods extended to music exposure in workplace (Section 8).


Specialized Methods: Section 7.3.1-7.3.3

1) Miniature/probe microphone in Real-ear (MIRE): Method is invasive (comfort, movement) Requires trained specialists to ensure safe

and consistent placement (e.g., audiologist) Can be resisted by workers

http://www.svantek.com/

Based on ISO 11904-1

(CSA Group with permission)

http://www.etymotic.com/



2) Manikin/artificial ears: Complicated logistics Need additional electronics and a

pair of matched headsets Worker free to move but device

must remain at close proximity

Type 3.3 Type 2 Type 1 (G.R.A.S.) (G.R.A.S.) (B & K)

Artificial Ears

Based onISO 11904-2(CSA Group with permission)

Acoustic Manikin (G.R.A.S.)

www.gras.dk/ www.bksv.com/www.gras.dk/

www.gras.dk/


Specialized Methods: Field Use



Transforming At-Ear to Sound Field

Long method (preferred):1) Measure 1/3 octave band levels at the ear.2) Convert to sound-field levels using conversion table. 3) Apply A-weighting and sum-up 1/3 octave bands.

Short method: Use single number to correct from at-ear to sound field

dBA levels (corrections based on AS/NZS standard). Manikin, Type 3.3, & Type 2: subtract 5 dB. Type 1: subtract 8 dB.

WARNINGRecent research indicates that single number corrections are not always in good

agreement with 1/3 octave band conversions because of factors such as the frequency response of the headset and the spectrum of the audio signal

(Nassrallah et al., 2013).


Specialized Methods: Example

Measurements of speech transmission in plane noise from David Clark headset using Type 3.3 artificial ear

Short method: Single Number Correction(A-weighted artificial ear measurement) – 5 dB

88.7 dBA – 5dB = 83.7 dBA

Long method: 1/3 Octave Band Conversion1/3 Octave

Frequency Band (Hz)Artificial Ear

Measurements (dB)Z107.56 – Table 1

Diffuse-Field Correction (dB)Z107.56 – Table 1

A-Weighting Factors (dB)A-Weighted, Diffuse-

Field Equivalent (dBA)100 83.4 0.0 -19.1 64.3125 87.5 0.3 -16.1 71.1160 92.5 0.6 -13.4 78.5200 86.9 0.9 -10.9 75.1250 87.6 1.2 -8.6 77.8315 83.3 1.4 -6.6 75.3400 81.2 1.8 -4.8 74.6500 81.6 2.3 -3.2 76.1630 78.1 3.2 -1.9 73.0800 76.3 4.0 -0.8 71.51000 79.1 4.6 0.0 74.51250 74.4 6.0 0.6 69.01600 76.4 8.1 1.0 69.32000 74.2 11.4 1.2 64.02500 72.4 15.0 1.3 58.73150 64.5 14.2 1.2 51.54000 61.7 11.9 1.0 50.85000 66.4 9.8 0.5 57.16300 72.2 8.5 -0.1 63.68000 68.0 11.0 -1.1 55.910000 52.7 7.1 -2.5 43.1

TOTAL = 85.7


Calculation Method: Section 7.3.4

• Simple tool to estimate (predict) noise exposure under communication headsets based on the relationship between the noise and signal sources:

• Recent analysis of the field data indicates a mean effective A-weighting listening signal/noise ratio (SNR) of 13.7 dB with a standard deviation 5.9 dB (Giguère et al., 2012).

• CAN/CSA Z107.56 specifies a SNR of 15 dB.• Research is being carried out to further validate the use of a

single number SNR.

External NoiseBN

Signal SourceS = BN – NR + SNR

Residual NoiseBN – NR

Noise ReductionNR



Example 1Non-attenuating

Headset

Example 2Attenuating

Headset

Background Noise BN 75 dBA 92 dBA

Noise Reduction NR 0 dBA 25 dBA

Residual Noise BN - NR 75 dBA 67 dBA

Signal Source S = BN - NR + SNR 90 dBA 82 dBA

Leq,t 90.1 dBA 82.1 dBA

Examples of noise exposure estimation under non-attenuating and attenuating headsets



• Equivalent sound level arising from all work activities involving headsets (Leq,t,headset) is given by:

t = duration that the headset is worn during the work shiftton = duration that the headset signal in on during the work shift

BN = measured A-weighted external background noise levelNR = A-weighted noise reduction of headset (if any), according to CAN/CSA Z94.2

SNR = effective listening signal to noise ratio = 15 dB

10/10/

,, 1010log10 SNRNRBNonNRBNheadsetteq t

tL

Residual NoiseBN - NR

Signal SourceBN – NR + SNR

• The 8-hr noise exposure level, Lex,8, is calculated by combining headset (Leq,t,headset) and non-headset (Leq,t,non-headset) work activities.


Calculation Method: Case Example

External background noise level (BN) 84.0 dBA

Noise Reduction of Headset (NR) 8.0 dBA

Effective background noise level when headset is worn (BN-NR) 76.0 dBA t = 6 hr

Effective headset communication signal level when present (BN-NR+SNR)

91.0 dBA ton = 4 hr

Equivalent sound level when headset is worn (Leq,6,headset) 89.4 dBA (headset usage 6 hr)

Equivalent sound level when headset is not worn (Leq,2,non-headset) 84.0 dBA (no protection 2 hr)

Total noise exposure level (Lex,8 ) 88.6 dBA T =8 hr

Exposure EstimationA headset with an effective noise reduction (NR) of 8 dBA is used in a background

noise BN of 84 dBA. The audio signal is present for ton of 4 hr out of a total headset usage t of 6 hr in a typical 8-hr work shift.


Calculation Method: Case Example

Assessment Option 1 Option 2 Option 3 Option 4

Background Noise BN 84 dBA 76 dBA - - 80 dBA

Headset Noise Reduction NR 8 dBA - 18 dBA - -

Signal to Noise Ratio SNR 15 dBA - - - -

Duration of Signal ton 4 hr - - 0.25 hr 1.5 hr

Duration of Headset Use t 6 hr - - - -

Work shift T 8 hr - - - -

Leq,t,headset (dBA) 89.4 81.4 79.4 79.9 81.5

Leq,t,non-headset (dBA) 84.0 76.0 84.0 84.0 80.0

Lex,8 (dBA) 88.6 80.6 81.1 81.2 81.2

Noise Mitigation


Exposure to Music, Radios: Section 8

• Music players, radios and other sound reproduction devices, used for leisure and/or work-related communications, must be operated normally when estimating noise exposure. For sources “far” from the ears (e.g. truck cab

radio), use SLM or noise dosimeter For sources “close” to the ears (e.g. headphone), use

specialized measurement methods specified in Section 7.3.1-7.3.3

• If it is not possible to operate the sound reproduction device at the time of measurements, when it is known to be used in the workplace, the calculation procedure in Section 7.3.4 shall be used with a SNR of 15 dB.


Exposure to Music, Radios: Example

Assessment

Background Noise BN 80 dBA

Fraction of Time Sound Device is Operating ton/t 0.5

Signal to Noise Ratio SNR 15 dBA

Leq,t,device operating BN + SNR + 10log(ton/t) 92.0 dBA

Leq,t,device non-operating BN 80.0 dBA

Leq,t (dBA) 92.3

Truck Cab Noise Exposure Assessment


Summary of CAN/CSA Z107.56-13

• Z107.56 proposes 2 types of methods to assess noise exposurefrom communication headsets: Specialized direct measurements (MIRE, manikin, etc.) Calculation method requiring only a SLM or noise dosimeter

and information on the noise reduction rating of headset.• WARNING : The calculation method provides only an indirect

estimate. If results are close to or above the criterion level(e.g., 85 dBA), noise control measures are needed, e.g.: reducing the external background noise, using headsets with a higher noise reduction rating, and/or limiting the output level and/or duration of headset use.

• If noise control measures are not sufficient to reduce calculatedexposure below the criteron level, measurements withspecialized methods are warranted.


Questionnaire - Survey

• Questionnaire to document: Use of communication headsets in the workplace Awareness of noise exposure under headsets Use and access to noise measurement equipment

• Distributed electronically to researchers, audiologists, occupational hygienists, acoustical consultants, health and safety workers in Canada.

• 75 respondents 11 in occupational hygiene


Questionnaire – Results

010203040506070

Excellentknowledge;

expert

Goodknowledge

Littleknowledge

Noknowledge

No answer

Perc

enta

ge

Awareness on noise measurement and hearing loss prevention

Occupational Hygienists Total Respondents

010203040506070

Excellentknowledge;

expert

Goodknowledge

Littleknowledge

Noknowledge

No answer

Perc

enta

ge

Awareness on the problem of noise exposure from communication headsets


010203040506070

Excellentknowledge;

expert

Goodknowledge

Littleknowledge

Noknowledge

No answer

Perc

enta

ge

Awareness on the techniques of noise measurement under communication headsets



Questionnaire - Results

Basic equipment:E.g., Sound level meter,

Noise dosimeter

Specialized Equipment:

E.g., Manikin, MIRE

Yes No Yes No

Occupational Hygienists 100% 0% 0% 100%

Total Respondents 53.3% 46.7% 32.4% 67.6%

Most have access to a sound level

meter and/or noise dosimeter

Most have access to a MIRE, followed by an artificial ear, and/or a

manikin

Access to basic and specialized equipment to measure noise levels in the workplace


Questionnaire - Results

• From these individuals, only four respondents (no occupational hygienists), had taken noise measurements under communication headsets in the workplace during their career.

0

10

20

30

40

50

60

70

Never Once 2-5 times 5-10 times 10 times or more

Perc

enta

geInterventions with regard to the use of communication headsets

Occupational Hygienists

Total Respondents


Conclusions

• CAN/CSA Z107.56 proposes 2 types of methods to assess noise exposure from communication headsets Specialized direct measurements Calculation method

• Calculation method is especially suitable for occupational hygienists given: Access to sound level meter or dosimeter is very

high (100%) while access to specialized equipment isvery limited (0%)

Good overall knowledge of issues pertaining to noise measurements and hearing loss prevention

Allow to take concrete actions and assess impact based on relatively simple calculations


ReferencesAbel, S.M. (2005). Hearing loss in military aviation and other trades: Investigation of prevalence and risk factors. Aviation, Space, and

Environmental Medicine, 76(12), 1128-1135.

Australian/New Zealand Standard. (2013). AS/NZS 1269-1:2005-13. Occupational Noise Management Part 1: Measurement andAssessment of Noise Immission and Exposure.

Canadian Centre for Occupational Health and Safety. (2011). Noise - Occupational Exposure Limits in Canada. Retrieved fromhttp://www.ccohs.ca/oshanswers/phys_agents/exposure_can.html?print.

Canadian Standards Association. (2013). Measurement of Noise Exposure, Canadian Standards Association CAN/CSA Z107.56-13,Mississauga: Canadian Standards Association.

Giguère, C., Behar, A., Dajani, H. D., Kelsall, T., and Keith, S. E. (2012). “Direct and indirect methods for measurement of occupationalsound exposure from communication headsets,” Noise Control Engineering Journal, 60(6), 630-644.

International Organization for Standardization (2002). ISO 11904-1: 2002. Acoustics - Determination of Sound Immission from SoundSources Placed Close to the Ear: Part 1: Technique Using a Microphone in a Real Ear (MIRE Technique).

International Organization for Standardization (2004). ISO 11904-2: 2004. Acoustics – Determination of Sound Immission from SoundSources Placed Close to the Ear: Part 2: Technique Using a Manikin (Manikin Technique).

Masterson, E. A., Tak, S., Themann, C. L., Wall, D. K., Groenewold, M. R., Deddens, J. A., & Calvert, G. M. (2012). Prevalence of hearingloss in the United States by industry. American Journal of Industrial Medicine, 56(6), 670-681.

Ministry of Labour. (2007). Amendments to Noise Requirements in the Regulations for Industrial Establishments & Oil and Gas-Offshore.Queen’s Printer for Ontario.

Nassrallah, F., Giguère, C., & Dajani, H. (June 2nd to 7th, 2013). Comparison of direct measurement methods for headset noise exposurein the workplace. International Congress on Acoustics, Montréal, Canada.

National Institute for Occupational Safety and Health (2009). Noise and Hearing Loss Prevention. Retrieved fromhttp://www.cdc.gov/niosh/topics/noise/abouthlp/soundadvice.html.

Occupational Safety and Health Administration (1999). “Evaluating noise exposure of employees wearing sound-generating headsets,”Report No.: TED 01-00-015.

Tak, S., Davis, R., & Calvert, G. (2009). Exposure to hazardous workplace noise and use of hearing protection devices among US workers- NHANES, 1999-2004. American Journal of Industrial Medicine, 52(5), 358-371.

Vaillancourt, V., Laroche, C., Giguère, C., Beaulieu, M.-A., & Legault, J.-P. (2011). Evaluation of auditory functions for Royal CanadianMounted Police officers. Journal of American Academy of Audiology, 22, 313-331.

Documents

New CSA Noise Standards and Noise Control - OHAO · Hearing Research Laboratory OHAO, Fall PDC Christian Giguère & Flora Nassrallah Toronto - October 23rd, 2013 New CSA Noise Standards