Transcript 3M Detction Noise Seminar 060313

Noise Measurement
Training Module
1
© 3M 2013. All Rights Reserved.
Table of Contents
 Physics of Sound (Hearing loss, terminology)
 OSHA (Regulations)
 Sound Level Meters
 Noise Dosimetry
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© 3M 2013. All Rights Reserved.
Noise Measurement and Dosimetry
Learning Objectives
 Explain sound pressure level, frequency & respective units of
measure
 Describe level average, time weighted average & dose
 Explanation of criterion, threshold & exchange rate
 Proper placement & care of microphones and instrumentation
 Explain hearing conservation regulations & OSHA
requirements as it pertains to noise measurement
3
 Hands on calibration, function & measurement with the noise
dosimeter, sound level meter and octave band analyzers
Section I
Physics
of
Sound
4
1-20
Sound vs Noise?
5
Why Measure Noise?
I.
Determine if the employee(s) are at risk for
Noise Induced Hearing Loss (NIHL) & should
be in a Hearing Conservation Program (HCP)
II.
Differentiate between on-the-job & off-the-job
noise exposure
III. Determine most effective hearing protection
IV. Engineering Controls
V. Administrative Controls
VI. Compliance with applicable Standards
6
© 2009 3M Company. All Rights Reserved.
Why Measure Noise?

Prolonged exposure to noise causes permanent and
debilitating hearing loss
 Mostly between 4 – 8 kHz
 Lose ability to understand speech in many situations
 Typically affects consonant reception
 Individual losing hearing is often the last to know!
7
Why Measure Noise?
 Long term health effects due to adrenaline release
 More accidents in high noise environments
 Measurable decrease in productivity
 Measurable decrease in work accuracy
 Increased fatigue
8
Noise Induced Hearing Loss
 Intensity + Duration
 Damage occurs in the cochlea
 Results in loss of
comprehension, not loudness
 Permanent
9
Definition of Sound
Fig. I-3 Compression & Rarefaction of air molecules
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What does Sound look like?
Adapted from Acoustics Animations – Dr. Dan Russell – Kettering University Applied Physics
http://www.kettering.edu/~drussell/Demos/waves/wavemotion.html
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Compression & Rarefaction of
Air Particles in a Sine Wave
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Four Characteristics Of Sound
 Frequency
(measured in Hz)
 Intensity
(measured in dB)
 Speed
(measured in feet or meters/second)
 Wavelength (measured in feet or meters)
13
Frequency
 Measured in Hertz (Hz)
 kHz for 1000xHz
 Relates to the pitch of the signal
 Is a measure of the cycles completed in one second
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Frequency – (Pitch)
Fig. I-4 1Hz and 10Hz Sine Waves
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Typical Frequency Examples
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 Lathe
50 to 1100 Hz
 Compressed air
500 to 8000 Hz
 Circular saw
300 to 12000 Hz
 Cars
8 to 1100 Hz
 Violin
300 to 9000 Hz
Frequency Response & Weighting
 The human ear is capable of responding to frequencies ranging

from 20 Hz to 20 kHz
 The ear is less efficient at high and low frequencies
 In the range from 500 Hz to 4 kHz a normal human ear is very
sensitive
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Frequency Response & Weighting
Fig. I-6 “A” and “C” Weighting Curves
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Sound Pressure Level
Fig. I-7 Sine Waves with different sound pressures
Measured in decibels (dB)
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2 Sine Waves:
Same Frequency
Same Time Duration
Different Intensity
One is TWICE as
loud as the other
Understanding deciBels (dB)
 deciBels S P L
dB SPL
 deciBels H L
dB HL
 Sound
Pressure
Level
 Hearing
Level
 Relates to intensity of
 Relates to measurements of
audiometric test tones
the environment
20
Doubling Sound Source
100 dB
100 dB
+
 Add 3 dB
 10 dB  perceived as “twice” as loud
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= 103 dB
Addition of Decibels
If the difference between two levels to be added is:
- 0 to 1 dB,
then add 3 dB to the higher number
- 2 to 3 dB,
then add 2 dB to the higher number
- 4 to 7 dB,
then add 1 dB to the higher number
- 8 dB or more, then add 0 dB to the higher number
 Decibels are logrithmic values
 They can not be directly added or subtracted
22
Changing Distance From Source
 Outside
 Doubling distance
 Decrease SPL 6 dB
 Room
 Very Near Source
 Twice the distance decreases
SPL by 6dB
 Far from source
 No change with change in
distance
NOTE: These are general
guidelines. Each case may vary.
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Octaves
Fig. I-11 Octave Bands
 Focus on the frequency content of the overall noise signal
 Important for noise control efforts
24
Occupational Noise Characteristics
Fig. I-12 Mixture of Source Signals
 In the real world of occupational noise the overall sound is a mixture of
many simultaneous sources with a variety of frequencies and intensities.
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Types or Characteristics of Sound
“Measure all continuous, variable and impact/impulse sound”
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Response Time
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 Slow
1 second rise and fall
 Fast
0.125 second rise and fall
 Impulse
35 millisecond rise
1.5 second fall
 Peak
50 microsecond rise and fall
Various time responses
28
29
Types of Hearing Protectors
 Muffs
 Plugs
Foam formable
Pre formed
Custom
 Others
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Plugs on a head band
Noise cancellation
Hearing Protection
NRR
Noise Reduction Rating
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NRR Devaluation
 NRR
- 7 dB
Adjusted
Attenuation
then divide this value by 2
to determine if hearing protector’s are adequate
to forego noise control
 The OSHA method is described well on the OSHA
Noise & Hearing Conservation e-Tool website
http://www.osha.gov/dts/osta/otm/noise/hcp/attenuation
_estimation.html
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Hearing Protection
2
33
NRR
- 7
NIOSH subject fit Model
 Muffs
NRR less 25%
 Formable Plugs
NRR less 50%
 All Other Plugs
NRR less 70%
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GRAPHIC ILLISTRATION
25
 Assume you need 10 dB
reduction
20
35
18
Muff
15
 Assume NRR is 24 for all
 De-rate muff by 25%
24
Formed
12
Others
10
6
 De-rate formable by 50%
5
 De-rate anything else by 70%
0
Net Protection
NRR
Plugs + muffs
 REMEMBER:
 Earmuffs over earplugs provide a maximum of 5dB
additional attenuation no matter what the muff rating.
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Critical Terminology
Criterion - If exposed to SPL on average for eight hours, it
would result in a maximum allowable exposure. [90dB for 8
hrs]
Threshold – dB level below which, all SPL’s are assigned a
value of zero. [80dB]
Exchange Rate - Results in a doubling or halving of the
maximum allowable exposure.
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Critical Terminology
Average Level (LAVG and Leq) - If present continuously, would
generate the same amount of energy as the varying levels that
are present in the environment measured in decibels.
Time Weighted Average (TWA) - A level average with an
assumed fixed sample period of eight hours measured in
decibels.
Dose - The allowable daily exposure value. A maximum
allowable exposure is equal to 100% dose. [90dB x 8hrs = 100%
Dose]
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A Basic Concept…
 TWA = Lavg @ exactly 8 hours
 DOSE = Follows the same line!
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Dose / Lavg over time
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Exercise I
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Exchange Rates
 SOUND LEVEL METERS
 3dB exchange rate
 When averaged, Leq (level equivalent)
 NOISE DOSIMETERS
 5dB exchange rate

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When averaged, Lavg (level average)
Criterion and 5 dB Exchange rate
 90dB x 8hrs = 90dB TWA = 100% Dose
 95dB x 8hrs = 95dB TWA = 200% Dose
 100dB x 8hrs = 100db TWA = 400% Dose
 100dB x 4hrs = 95dB TWA = 200% Dose
 100dB x 2hrs = 90dB TWA = 100% Dose
 100dB x 1hr = 85dB TWA = 50% Dose
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Section II
OSHA
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21-25
The Occupational Noise Exposure Standard
 Derived from the Walsh-Healey Public Contracts Act.
 1971 adopted under the Occupational Safety and
Health Act.
 Permissible Exposure Level (PEL) of 90 dBA.
 Noises with a higher level than 90 dBA can be
sustained for periods of less than 8 hours.
 Sounds with average levels less than 90 dBA can
persist for periods of more than 8 hours.
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Permissible Noise Exposure
Hours per Day
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Sound Level dBA slow
response
8
90
6
92
4
95
2
100
1.5
102
1
105
0.5
110
0.25 or less
115
Hearing Conservation Amendment
 Published in the Federal Register on March 8, 1983.
 The Hearing Conservation Amendment requires the employer to perform
five key tasks:
 Measure Noise
 Audiometric Tests
 Hearing Protectors
 Education & Training
 Record Keeping
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Table G-16a (abbreviated)
Measuring Threshold
H.C. Action Level (50% exp.)
8 Hour Criteria
Minimum Upper Range
48
24
85
A-Weighted
Sound Level
Duration
(Hours)
80
16
90
95
100
105
110
115
120
125
130
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8
4
2
1
0.5
0.25
0.125
0.063
0.031
Section II
Measuring Method for OSHA Surveys
Original Rule
H.C.A.
A/Slow
A/Slow
Exchange (Doubling) Rate
5 dB
5dB
Criterion (LC=100%)
90dB
90dB
Threshold (Cut Off)
90dB
80dB
Weighting/Response
Limit
90dB/100%
(PEL)
49
85dB/50%
Action
Level
Conclusion
 The focus of the Occupational Noise Exposure Standard and the Hearing
Conservation Amendment, is to set minimum requirements to protect
hearing for those workers in a noisy environment.
 The Keys to Success
 Positive attitude on the part of the management
 Clear communication of the value of hearing
 Hearing protection takes care of the problem of noise for the short term, but the
key to real hearing protection is education and communication.
50
Section III
Sound Level Meters
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26-39
Components of a Sound Level Meter
Fig. III-1 Block Diagram of a Typical Sound Level Meter
Microphone
Amplifier
Range
Control
Frequency
Filter(s)
C
A
Fast/Slow
F
S
52
Display
Classification of Sound Level Meters
 Three types of SLM’s established by ANSI, and IEC Standards:
 Class 0 Laboratory grade instrument
 Class 1 Precision instrument
 Class 2 General purpose instrument
53
Types of Microphones
Random
Incidence
54
Direct
Incidence
Pressure
Microphone
Acoustical Calibrators
1) Loudspeaker
1
2) ON/OFF switch
3) Battery indicator
4) Microphone adapter
2
4
3
55
SoundPro SE/DL series
Understanding the KeyPad
Enter key ~
The center key is primarily used to
execute an action from the menu
displays or in measurement and
logging displays.
Arrows ~
The left/right arrows and up/down
arrows are used to navigate in the
direction you select. These are used
often as you are moving through the
menus or toggling through logged
sessions.
Alt f key ~
Alternate functions. Pressing this key
toggles the contents in the Softkey
Region.
On/Off/Esc ~
Triple function key. Its function
depends on the circumstances at
that time. Press it to apply power
and switch the instrument on. Press
it to power down . Press it to
Escape (or exit) from a data field or
a screen.
Run/Pause key ~ Press to start and pause studies
depending upon whether a study
was running at that time or not.
Stop key ~
Press to stop (or close) the session.
Backlight key ~ If you have Backlight set to
“Manual,” press this key to manually
turn the backlighting on or off.
56
SoundPro Exercise I – Calibration & Battery Check
 Page 32 – In workbook
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SoundPro Exercise 2: Measurement of Noise Sources
 Pages 33 & 34 – In workbook
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Sound Level Meter Placement Keys
 Location, Location, Location
 Reflection
 Vibration
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60
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Section IV
Noise Dosimeters
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Noise Dosimeter Components
Microphone
Amplifier
Range
Control
Frequency
Filter(s)
C
Fast/Slow
F
S
A
Display
Computer
63
Storage
Printer
Calculator
Clock
Meter
Environmental Concerns
 Temperature
 Humidity
 Atmospheric Pressure
 Wind
 Radio Frequency Interference
64
 Magnetic Interference
How To Do A Noise Survey
 Check Battery
 Leave It Alone
 Reset Unit
 Work
 Check Set Up
 Check It
 Calibrate Unit
 Observe
 Inform Worker
 Remove Unit
 Unit Placement
 Record or Download Data
 Microphone Placement
65
© 2009 3M Company. All Rights Reserved.
Survey Techniques
I.
Individual Full Exposure Assessment
II.
Representative Sampling
III. Task-Based Exposure Assessment Modeling
(T-Beam)
IV. Area Mapping
66
© 2009 3M Company. All Rights Reserved.
67
© 2009 3M Company. All Rights Reserved.
Survey Methods
68
Managing Mobility and Variability
 5 day , 40 hour evaluation
69
Infrequent Exposures
 The day OSHA inspects
is reality
 Use informative signs
 Use HPD’s
70
Re-monitoring
 Change in process or procedure that affects
inclusion and/or hearing protection
effectiveness
-production rates
-material processed
-production technique
-machine placement
71
Survey Pitfalls!!!
 Microphone Placement
 Employee
 Project Assumption
 Threshold Distortion
 Wind
 Battery & Calibration
72
What To Record In Addition To Sound Levels
 Dates and Times
 Model and Serial Numbers
 Pre and Post Survey Calibration Levels
 Workplace Descriptions
 Task Descriptions
 Environmental Factors
 Instrument Settings
 Unusual Conditions
73
Noise Dosimeters
74
NoisePro Dosimeter Key Pad Functions
The RUN/PAUSE button is pressed to Start and
Stop integration and data logging.
The Enter key is used to accept values or actions
in the Setup menu.
75
The RUN/PAUSE button is pressed to Start
and Stop integration and data logging.
The ON/OFF ESCAPE key has two functions. It is
used to turn the instrument on and off. If also
serves as an escape key in the instrument setups
Microphone Placement
76
Proper Mounting
Typically Belt
Mounted
77
Middle of Shoulder
NoisePro: Exercise I - Calibration
 Page 54 in Workbook
78
NoisePro: Exercise 2 – Noise Measurement for
OSHA Compliance
 Pages 55 & 56 in Workbook
79
© 3M 2013. All Rights Reserved.
Measuring Dose

Using the 5 dB exchange rate (doubling rate), we can conclude the
following:
80
95 dB for
8 hours
equals
200%
dose
100 dB for
8 hours
equals
400%
dose
105 dB for
8 hours
equals
800%
dose
110 dB for
8 hours
equals
1600%
dose
NoisePro: Exercise 3 – Effects of Exchange Rate &
Criterion
 Pages 55 & 56 in Workbook
81
© 3M 2013. All Rights Reserved.
Tim Bailey
3M Detection Solutions
Phone: (800) 245-0779, ext. 152
Fax: (262) 567-4047
[email protected]
Customer Service: Heidi Tunak, ext. 106
Tech Support: Randy Sleggs, ext. 123
Mark Scherer, ext. 158
82
What We Measure
Fig. I-13 RMS (Root-Mean-Square)
83
Crest Factor
Fig. I-14 Crest Factor - Impulse/Impact Noise
84