Noise Intensity of Construction Tools

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Noise Fundamentals
2
HOW DO WE HEAR?
3
SOUND RECEPTORS
4
DAMAGED HAIR CELLS

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High Sound Levels (Noise) can be Detrimental to
Hearing, especially when exposure is for an
extended periodThis is a fact and it is widely
known and almost common knowledge, and yet,
little is done to protect workers from the
harmful effects of noise
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Noise Induced Hearing Loss
Exposure to noise causes a loss of sensitivity to
high frequency (high pitch) sound. Continued
exposure results in damage to mid frequency
region as well. One can experience progressive
high frequency hearing loss and not be aware of
it until it becomes severe (doesnt affect
loudness perception).
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HOW CAN IT HAPPEN?

• One Time Exposure To Loud Sound
• OR
• Daily Exposures To Moderately
• Loud Sounds

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Why is there so little done to protect workers
from noise?
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• Noise is possibly annoying,
• but it is not physically painful

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The effects of noise on hearing loss occur
slowly, unnoticed from day to day exposure to
equipment surrounding workers
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Fellow Workers on most construction projects also
do not wear hearing protection
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• Hearing protection might be regarded as a bother
  to many construction workers
• Workers may not know the sound level at work..

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Basic Information on Noise Should Be Understood
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Sound Fundamentals
Sound radiates outward from the source in all
directions and the sound intensify diminishes
with distance from the source.
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How Much Does the Sound Intensity Diminish with
Distance from the Source?
Distance 1 or D1
Distance 2 or D2
The Change in the Decibels from D1 to D2 is 20
log (D2/D1) When the distance doubles, the
decline is 6 db
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D4
D3
D2
D1
6 db drop
6 db drop
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How much does the noise level actually decline
with distance?

• The decline of 6db when the distance from the
  source is doubled is based on no encumbrances
  (e.g. no sound reflected from objects), but this
  is not the real world

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Testing of Construction Tools

• Common Construction Tools were Selected
• Sound was Measured in a Laboratory Setting
• Repeated Measures were Taken for Statistical
  Reliability

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Why Does the Sound not Decline as Computed?

• Sound is reflected from the concrete floor
• Sound is reflected from the block walls
• Sound is reflected from other objects

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Some Acceptable Levels of Noise Exposure have
been Established
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Common Sound Levels

• Library 40 db
• Conversation (3ft) 70 db
• Garbage Disposal (3ft) 80 db
• Lawnmower (3ft) 100 db
• Concert 110 db
• Threshold of Pain 130 db

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Safety Regulations on Permissible Noise Exposure
each day

• 8 hours 90 db
• 4 hours 95 db
• 2 hours 100 db
• 1 hour 105 db
• ½ hour 110 db
• ¼ hour 115 db

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What Kinds of Noise Levels are Construction
Workers Exposed to?

• This was explored in a study of power tools that
  are commonly used on construction projects
• Measured 150 mm from the tool (not cutting)
• Max RPM

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Planer 118 db
Grinder 119 db
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Jigsaw 112 db
Belt Sander 108 db
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Router 103 db
Circular Saw 102 db
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Drill 73 db
Chisel 85 db
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Sound Levels of Tools when Running at Maximum RPM
vs Cutting or Working on Wood
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Sound Intensity (db) of A Circular Saw at 600 mm
(approx distance from the tool to the operators
ear)
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Sound Intensity when a 2nd Noise Source is added

• Sound level of 1 saw 94.8 decibels
• Sound level of 2 saws 99.7 decibels
• Computed sound level of 2 saws 97.2

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Hearing Protection

• NRR - Noise Reduction Rating
• The NRR describes the average sound level
  reduction (attenuation in db) provided by a
  hearing reduction device.
• In order to ensure maximum hearing protection two
  variables are important
• the fit of the hearing protector
• the importance of wearing the hearing protector
  during the entire time the wearer is exposed to
  excessive or dangerous noise levels
• 33 Is Highest Possible Rating

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Hearing Protection
NRR of 22
NRR of 29
NRR of 30
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DOUBLING UP!

• Use of insert earplugs and circumaural earmuffs
  together

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Conclusion

• Workers are probably exposed to higher levels of
  noise than would be predicted