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NOISE EXPOSURE ASSESSMENT

Sampling Strategy and Data Acquisition

Defining Terms

NOISE, n. 1) A stench in the ear. 2) Undomesticated music.3) The chief product and

authenticating sign of civilization. Ambrose Bierce (1842 – 1914?)

American journalist, short-story writer, satirist, and smarty pantsThe Devil's Dictionary

Noise Exposure Assessment

WhyRationaleStandardsResources

WhoSample selectionSampling sufficiency

HowInstrumentationMethodologies

WhatData managementReporting

What’s the objective?

Improved understanding of exposure and risk makes for a better programHCP inclusionHPD selectionAudiometric interpretationWork relatednessRecordability

Hearing loss prevention

Key Questions

Who is in the HCP? What HPD is OK for

jobs/workers? Is this employee OK

for this job? Match the worker

and the job

Is the employer responsible for HL?Work comp Recordkeeping

Key Answer

Consider how data will be used Today Tomorrow Forever

Application of data drivesSampling protocolAccuracy requirements Instrumentation selectionQualifications of surveyor

Risk Management

Assess RiskNoise Exposure Assessment

Mitigate RiskNoise Control

Hearing Protection

AssessEffect

Hearing Testing

Quality of program HERE drives …

Integrity of program here.

Is Noise still a deal?

2004 2005 2006 2007 2008 2009 2010

220,700 215,500 203,600 183,300 165,200

146,700 138,400

28,400 26,90024,400

23,00022,100

19,500 18,800

Hearing Loss Recordability Trend

163,100 hearing losses since 2004

© 3M 2010. All Rights Reserved.

2nd largest specific illness

98,300

24,900

18,800 12,800 2,400

2010 by Injury TypePrivate Industry Only

All Other

Skin

Hearing Loss

Respiratory

Poisoning


Overwhelmingly Mfg

14,700

1,600

2,500

Manufacturing

Transportation andWarehousingEverything else


Damage-risk Criteria Reminder

Organization Exposure Level dB(A) Excess RiskISO (1975) 90 21%

85 10%80 0%

EPA (1973) 90 22%85 12%80 5%

NIOSH (1972) 90 29%85 15%80 3%

Risk of material hearing loss (HTL >= 25 dB) above that anticipated in non-noise exposed population. Based on 40-year working lifetime.

Risk is Related to Exposure

Damage RIsk Criteria

010203040506070

75* 80 85 90 95*

Exposure

% e

xces

s ris

k

ISO EPA NIOSH

Deeper Look at Damage Risk

From NIOSH White Paper (5/2012)Selection of Audiometric Frequencies included in analysis

0.5-1-2 kHz 1-2-3 kHz 1-2-3-4 kHz

Avg Exp Level,dBA

ISO 1971

NIOSH 1972

EPA 1973

ISO 1990

NIOSH 1997

NIOSH 1972

ISO 1990

NIOSH 1997

ISO 1990

NIOSH 1997

90 21 29 22 3 23 29 14 32 17 25

85 10 15 12 1 10 16 4 14 6 8

80 0 3 5 0 4 3 0 5 1 1

•More recent work identifies higher frequencies as key for verbal communication•Analysis-dependant – inclusion of higher frequencies increases population

14

Is it the labeling process? NRR

EPA testing and labeling requirements

Lab based Unreliability leads to deratingOSHA: (NRR-7)/2NIOSH: Variable by type

Pressure on mfr.

Label value is inaccurate Variability in even lab data Typical SD 3-5 dB per frequency

Test Frequency 125 250 500 1000 2000 3150 4000 6300 8000 NRR

Mean 37.4 40.9 44.8 43.8 36.3 41.9 42.6 46.1 47.3 29SD 5.7 5.0 3.3 3.6 4.9 3.0 3.1 3.5 2.7


Standards

Protocol Standards ANSI S12.19-1996 (R2001) Measurement of Occupational Noise Exposure

ISO 9612 Acoustics – Measurement and calculation of occupational noise

exposure – Engineering method ANSI A10.46-2007 HLP for Construction & Demolition Workers

Instrumentation Standards ANSI S1.4-1983 (R2001) Sound Level Meters ANSI S1.25-1991 (R2002) Dosimeters ANSI S1.40-1984 (R2001) Calibrators

Good Practice Guidelines

The Noise Manual, 5th Edition Berger et al AIHA Press 2000

A Strategy for Assessing and Managing Occupational Exposures, 3rd Edition AIHA Press 2006

NIOSH Criteria for a Recommended Standard: Occupational Noise Exposure DHHS (NIOSH) Pub. No. 98-126

NIOSH Preventing Occupational Hearing Loss: A Practical Guide DHHS (NIOSH) Pub. No. 96-110 • NIOSH Documents

– 1-800-356-4674 or– www.cdc.gov/niosh/topics/noise/pubs/no_pubs.html

Noise Refresher

Intensity/loudness Decibel 1/10 of a bel An Alexander Graham Bell to be

precise 1 dB barely audible 3 dB clearly audible Energy doubles @ 3 Loudness doubles @ 10 Risk doubles @ 3 or 4 or 5

Frequency Measured in CPS Expressed as hz Middle C = 256 hz

Lee’s Corollary

Sound or Noise vs Exposure Noise People Time

E = N*P*T

As N, P, or T approach zero, so should our concern!

Who do I sample?

Work Force Characterization EAS Strategy

Similar exposure groups (SEG) Groups of workers with similar risk of

exposure Similar location Similar operations Similar risk of exposure?

Base organizational unit Representative Personal Monitoring

Setting UP SEG

At the core, SEG is representation of how the facility operates Who works where? What do they do? How do they group?

Existing personnel infrastructure Department Job Classification

Existing production infrastructure Processes Tasks

Resources A Strategy for Assessing and

Managing Occupational Exposures, AIHA Press 2006

Quick Overview 5 Steps to Industrial Hygiene

Exposure Assessments ISHN January 2006, Spear

AIHA Noise Manual, Chapter 7

Alternative Selection Strategies

Random Sampling Sufficient Days People Conditions

To represent conditions

Within SEG better

Targeted Sampling– “I only sample where I

know I have a problem”– STS/Hearing Loss

A little late, don’t you think?

– Evident problemsMay miss

– Mobility– Intermittency

How much sampling?The Sufficiency Question

Understanding that the objective in most cases is to conduct minimum sampling required to sufficiently represent SEG…1. Statistical reliability2. ISO 96123. Professional judgment

Sufficiency from 1981 US Regulation

Number of employees Employees measured (percent)

1 to 19 100

20 to 49 60

50 to 99 50

100 to 249 40

250 and over 30

From 1981 draft of 1910.95

1. Statistical reliability

As above to Include One or More Observations for Employeeswith Exposure in the Top 10% of the Distribution

Size of Group (N) 12 13-14 15-16 17-18 19-21 22-24 25-27 28-31 32-25 36-41 42-50 51+

29Required # of Measured 12 13 14 15 16 17 1811 19 20 21

Sample Size Needed to Ensure at the 95% Confidence Level thatthe Sample Will Include One or More Observations for Employees

with Exposure in the Top 20% of the Distribution

Size of Group (N) 7-8 9-11 12-14 15-18 19-26 27-43 44-50 51+

9 10 11 12 14Required # of Measured 6 7 8

From Leidel, Busch & Lynch, 1977

Caveat

“… use of a statistical sampling procedure … does not alleviate the employer’s responsibility to identify all those workers with doses of 50% or more.”

Royster, Berger and RoysterChapter 7, AIHA Noise Manual, 5th Edition

2. ISO 9612 – time not people

Number of workers in the SEG (nG)

Minimum cumulative duration of measurement to be distributed over the

homogenous exposure groupnG ≤ 5 5 hours

5 ≤ nG ≤ 15 5 h + (nG − 5) × 0,5 h

15 ≤ nG ≤ 40 10 h + (nG − 15) × 0,25 h

nG ≥ 40 17 h or split the group

At “Job Level” measurement

3. Professional Judgment

With: Appropriate SEG selection

Detailed analysis of exposure conditions

Carefully selected sampling protocol

Sufficient time with the operations

Your judgment can be a viable substitute for statistical analysis

Preparation Environment

Conditions

Workforce dynamic

Understand implications of decisions This is your HCP!!!

Document decisions

Concentrate on borders Test is Repeatability

Can you do it again and get similar results?

Instrumentation and Protocol

Precision Calibration

Field Laboratory

The Instruments SLM ISLM Dosimeter

Instrumentation and Protocol The Mystery of the Meter

How can I take one measurement and come up with 14 different results?

Or …It’s only noise - how can this

*#%*$ thing put out so many numbers?

From a leading mfr website

“…then the high performance … is your noise dosimeter. This Type 1 noise dosimeter logs Lavg/Leq, FastMax, SlowMax, FastMin, SlowMin, Fast Ceiling Count, Slow Ceiling Count and Lpeak at intervals from 1 second up to 1 hour.” Editorial aside: 8 parameters recorded every second 480 data points per minute 28,800 data points per hour 230,400 data points per 8-hour shift

“It includes (4) virtual noise dosimeters to measure (4) separate noise standards.” Editor, again: 921,600 data point per shift

Paralysis by Analysis

Noise Exposure Descriptors

Averages TWA TWA8

Lex,T LEX,8h

Lavg LpAeq,T

Leq Leq,T

LOSHA

Response Slow Fast

Regulatory Criteria Threshold Criterion Level Time

Action Level Doubling,

Exchange or Trading Rate

Single Events Lmax Lmin Lpeak

Other Criteria Environmental Ldn or DNL

Meter Stuff Crest rate Dynamic range

Weighting Networks

Attempt to make the instrument respond to noise like the human ear

The ear works differently at different levels

Equipment AccuracyFreq range Hz

Type 0 Type 1 Type 2

31.5 to 2000

± 1 +1.5, -1 ± 3

2000 to 4000

± 1.5 +2.5, -2 +3, -4

4000 to 5000

± 1.5 +3.5, -3 +4, -6

5000 to 6300

± 2 ± 4 +5, -8

6300 to 8000

± 3 ± 5.5 +8, -9

8000 to 10000

± 3.5 +7, -8 Not specified

10000 to 12500

± 4.5 +8, -11 Not specified

Type 0 – Laboratory grade

Type 1 – Engineering grade

Type 2 – Survey grade

Untyped – Radio Shack™ grade

What’s the difference?– Accuracy– Cost– Primarily microphone

Keep precision level in mind when making decisions

Calibration

Field Function test Pre-sampling Post-sampling

What is checked? 1 or 2 frequencies 1 level

Data is as good as the last calibration. You make the call …

Laboratory All instruments

Including calibrator ISO call it

“measurement chain” Annually?

Current Reading SLM

Screening tool No ability to time-weight or average

Cheap and plentiful Free for your smartphone $63 in Spring 2004 Lab Safety catalog $35 - $50 from Radio Shack NI 100 $40

NOT for exposure assessment May not be NIST traceable Doesn’t integrate

BUT great training tool Awareness General HPD guidelines

Integrating Sound Level Meter

Most function as dosimeters and vice versa

What’s the difference? Dosimeters designed to be small ISLM designed for function Many w/OBA capabilities Some available as Type 1

Like dosimeter, internal averaging Like SLM, real-time short duration

readout

ISLM - Techniques

Equipment Placement for Exposure Assessment

Surveyor-heldMic positioned in

hearing zone of workerSimulated

Task-Based Monitoring (T-BEAM)

Representative Job Operate Transfer Press #929

Jobs are broken into primary component

tasks

SEG: Transfer Press Operator

Task 2 - Breaks

Task 3 - Monitor #929

Task 1 - Lunch

Task 4 - Unload and Stack Parts

Task 5 - Cleanup w/Broom

Task 6 - Cleanup w/Air Wand

ISO 9612 Task Level

T-BEAMTable G16a

Extracted portions

SPL Reference

Duration

80 32

81 27.8

82 24.3

83 21.1

84 18.4

85 16

86 13.9

87 12.1

88 10.6

89 9.2

90 8

91 7

92 6.1

93 5.3

94 4.5

95 4

96 3.5

97 3

98 2.8

99 2.3

100 2

%D = (C1/T1 + C2/ T2 + … Cn/ Tn)

Where:

%D is percent dose

C is time at a given sound level

T is allowable time at that sound level from appropriate tables (G16, G16a)

Exchange rate factored into tables

Task-Based Noise Exposure Profile

NIOSH DOSES

NASA TWA Calculator

ExampleAnalysis

Sampling Strategy

T-BEAM

Dosimeter

Integrates Exposure over time

Averages Histogram Weapon of choice for

many Curse of the Carbon

Tube

Dosimeter Techniques

Equipment PlacementMicMid-shoulderOther

Under hood

Instrument Belt Vest Other New technology

Dosimeter Techniques

Sample length Sufficiently long to proportionally represent all

tasks performed by the employee Partial shift OK if: Tasks in representative proportionNo early or late task outliers

Short dosimeter samples can be combined as tasks

Cumulative per ISO 9612

Dosimeter Histogram

Area Plot: Minute Average Sound Level Measurements for a Dosimetry Sample

707580859095

100

6:16

:09

6:48

:00

7:20

:00

7:52

:00

8:24

:00

8:56

:00

9:28

:00

10:0

0:00

10:3

2:00

11:0

4:00

11:3

6:00

12:0

8:00

12:4

0:00

13:1

2:00

13:4

4:00

14:1

3:24

Time (Minutes)

Soun

d Le

vel

((dB

(A))

Seam grinder in a Truck mfg. plant full shift; 1 minute avg.

TWA 90.8; Lmax 104.6; Lpk 125.6

Dosimeter Cautions

Contamination Particularly single events Conversation, esp. at boundaries

Start sample after placing micObservation

Required under S12.19 Corroborating SLM measurements New technologyRemote viewer

Sampling During Breaks?

During lunch and break periods, the dosimeter should be: Left on Turned off Removed Placed on different employee Recalibrated Data should be edited in post processing

Well ….

Dosimeter – New Stuff

Either: Real smart, or Real dumb

Dan Johnsons’ Dream Etymotic Research

Remote monitoring

Interpreting the Data

Data applications HCP selection HPD selection

Statistical Model USAEG TG 181

ISO 9612 Professional Judgment

USAEHA TG181 One of MANY statistical approaches

AIHA Noise Manual Chapter 7 for more statistical options Developed by US Army Thanks to Felix Sachs for sharing

Protocol: Determine SEG Stratified random sampling within group Days Conditions People

Use Leidel & Busch to determine amount of sampling Assign each individual a number from 1 to N Use Random Number Table to select candidates

USAEHA TG181

Determine Individual Exposures (LTWA(8HR)) Dosimeter T-BEAM

Calculate Group TWA Risk Compute one-sided upper tolerance limit (UTL) for

the 90th percentile with a 75% confidence limit

Consider discarding TWA values below 80 dBA or rounding up to 80 to avoid scatter*

* Editorial comment: depending on dosimeter settings, this may or may not be a good idea.

Upper Tolerance Limit

UTL = x + K s

Where:• UTL is upper tolerance limit

• 90th percentile with 75% confidence

• x is the mean of the sample values • K is one-sided tolerance limit for normal distribution

• from table• s is the unbiased standard deviation of the sample values

# Msmts.

K Factor for 90th

Percentile with 75%

Confidence3 2.5014 2.1345 1.9616 1.8607 1.7918 1.7409 1.702

10 1.67111 1.64612 1.62413 1.60614 1.59115 1.57716 1.56617 1.55418 1.54419 1.53620 1.528

ExampleAnalysis

TG-181

Bayesian Statistics

• Can you combine:• Your sampling data• Your best judgment• Other factors?

• Sure – with conservative results

Bayesian Analysis

ExampleAnalysis

What would YOU do?

Date Exposure Group Duration Proj. Dose TWA (dBA) Leq

2/22/2006 1 482 8.7 72.4 72.3

2/23/2006 1 486 10.9 74.0 73.9

2/24/2006 1 512 4.7 67.9 67.5

2/24/2006 2 509 9.6 73.1 72.6

2/22/2006 2 485 18.3 77.7 77.7

2/23/2006 2 488 28.0 80.8 80.7

2/24/2006 2 510 17.0 77.2 76.8

2/22/2006 2 497 14.3 75.9 75.7

2/23/2006 2 488 25.9 80.3 80.1

2/22/2006 2 499 54.5 85.6 85.3

2/23/2006 2 487 25.5 80.1 80.0

2/24/2006 2 510 13.0 75.3 74.8

Measured Data TWA 75-90

UTL(A) = 84.8

UTL(G) = 84.7

Measured Data Dose 75-90

UTL(A) = 45%

UTL(G) = 43%

ISO 9612 Uncertainty Calc

Daily Noise Exposure Level 80

Expanded uncertainty 4.3

Bird et al, JOEH, June 2004

Of 20 SEG, 14 have at least some exposure over HCP criteria

“… use of a statistical sampling procedure … does not alleviate the employer’s responsibility to identify all those workers with doses of 50% or more.”

Royster, Berger and RoysterAIHA Noise Manual 5th Edition

Who’s in the HCP?

How about now?

Four fossil fuel power plants with 5 SEG

Example Applicaton

Accuracy and Classification

TWA (dBA) Classification84 or lower A

85 – 89 B90 – 94 C95 – 99 D

100 or above E

Keep accuracy limitations in mindClose scrutiny at borderlinesConsider class or group alternatives

Noise exposure classification scheme from Noise Manual, Roysteret al

AIHA Exposure Assessment StrategyHealth Effects Lee’s dBA Est Exposure Rating Categorization

Life-threatening or disabling illness

4 >105

Irreversible health effect of concern

3 90-105 4 >Long-term Average Occupational Exposure Limit

Severe reversible health effect of concern

2 85-90 3 50% to 100% LTA-OEL

Reversible health effect ofconcern

1 80-85 2 10% to 50% LTA-OEL

Reversible effect of little concern, or no known or suspected adverse health effect

0 <80 1 <10% LTA=OEL

ISO 9612

Type of Work Measurement StrategyTask level Job level Full day

Fixed workstation – simple or single task OK; PFixed workstation – complex or multiple tasks OK; P OK OKMobile worker – predictable work, small # tasks OK; P OK OK

Mobile worker – predictable work, large # tasks or complex work pattern

OK OK OK; P

Mobile worker – unpredictable work pattern OK OK; P

Fixed or mobile worker – multiple tasks with unspecified duration

OK; P OK

Fixed or mobile worker – job goal based w/no specific tasks

OK; P OK

OK = acceptable protocol P = preferred protocol

ISO 9612 - Task level

Noise as related to tasks 5 min minimum sample length unless task shorter 3 iterations of each task minimum

If <3dB different, use average If >3dB different

Subdivide tasks or Minimum 3 additional measurements

Task duration Interview Observation Arithmetic average

Daily exposure Compile like T-BEAM Watch for Lpk

ISO 9612 – Job Level

Average job-related measurement Workstation full cycle

Calculate uncertainty If uncertainty >3.5 dB

Reevaluate SEG Collect more data to

reduce uncertainty

Number of workers in

the SEG (nG)

Minimum cumulative duration of measurement to be distributed over

the SEG

nG ≤ 5 5 hours

5 ≤ nG ≤ 15 5 h + (nG − 5) × 0,5 h

15 ≤ nG ≤ 40 10 h + (nG − 15) ×0,25 h

nG ≥ 40 17 h or split the group

ISO 9612 – Full Day

Minimum 3 full day samples If <3dB different, use average If >3dB different At least 2 additional samples

Average measurements to represent SEG Calculate uncertainty

ISO 9612 – Uncertainty

Mechanism to address and quantify variability Instruments Imperfect selection of measurement position Sampling

Combine to develop combined measurement uncertainty ISO Guide to the Expression of Uncertainty in

Measurement (GUM)

ISO 9612 Annex C: Task Level

Uncertainty factors: sampling of noise level estimation of duration of task instrumentation microphone location

Sensitivity coefficients weight uncertainty Expanded uncertainty

Combined uncertainty * K K = 1.65 To achieve 90% confidence

ISO 9612: Job and Full Day Level

Uncertainty primarily from number of samples Detailed approach in standard Quickie estimation

(LeqMax – LeqMin)/K Where K = 2.2 if N < 6 K = 2.5 if N ∈ [6, 15] K = 3.0 if N ∈ [16, 30]

And N = number of samples

Survey Reports

Think about purpose Communicate results Assign exposure to individuals based on representative

monitoring Record

Noise Manual Format Purpose/objective Summary

Results Conclusions

Procedure Standards Instrumentation Standards Calibration Records

Data

ISO 9612 Format

General Purpose Who

Client Surveyor

Work Analysis SEG definition Definition of “normal day” Msmt strategies

Instrumentation Calibration traceability

Measurement description Who/SEG When Instruments Conditions

Production Non-relevant

Measurement Mic position/location Duration Count Results

Conclusions Uncertainty

Lee’s Suggestion

Executive Summary Introduction

Table of Findings Medical & Safety Report

Survey Layout/Map Appendix

Calibration records Surveyor certifications

Executive Summary

Overview Number or % of

workforce at risk Estimate HCP costs

Use pictures Use trends

0%

50%

100%

Noise Exposure Trend

>100 dB TWA 20 10 0 0

90 - 100 dB TWA 250 225 200 180

85 - 90 dB TWA 450 400 375 375

80 - 85 dB TWA 900 1000 950 1050

<80 dB TWA 1250 1300 1450 1600

1998 2001 2003 2005

Noise Exposure Distribution 2005

49%

33%

12% 6% 0%<80 dB TWA80 - 85 dB TWA85 - 90 dB TWA90 - 100 dB TWA>100 dB TWA

Medical and Safety Reports

Exposure (TWA or Dose) Representative data back to people HCP Inclusion and Selection Who makes this decision?

Hearing Testing/Audiogram Medical or functionary Scheduling

HPD Purchasing Safety

What does it look like?

Noise Survey Summary Report June 2011

Dept Job Code Job Description TWA Lmax Lpk Min NRR

245 Machines 846 Material Handler East 87 94 9

245 Machines 846 Material Handler West 82 88

245 Machines 848 Machine Operator Bradley 92 99 126 14

245 Machines 848 Machine Operator Headlee 89 96 114 11

292 Operations 912 Maintenance Millwright East 78 99 135

292 Operations 915 Electrician 81 102 118

Engineering Reports Does the survey contain enough to drive

controls program? Sources Prioritization

Who are the engineers? InsideOutside Vendors

Worker

Sound Survey Map

Consider application HPD enforcement Noise status

Consider utility Colors Grid patterns

Contour Mapping

Good “picture” of noise in the plant Typically bad picture of exposure

from Pelton, 1993SoundPLAN, navcon.com

HPD Zone Layout

Built on existing administrative boundaries

Good for HPD Good for

worker notification

May overstate exposure

Other potential inclusions

HPD Audit HCP Audit Exposure by department

Trend

Source identification Controls?

How about recommendations?

Do your clients expect recommendations with the survey report?

Be cautious Don’t overstate your experience or capability Who collected the data?

Difference between identifying problems and suggesting solutions

Client liability exposure

83

Making it Work

Preparation Understanding

Protocol Conditions Limitations

Application… as research continues …

Courtesy Audibel
