Noise and Hearing Conservation

1
Noise and Hearing Conservation

• Physics of Sound and Protection of Hearing in the
  Construction Industry

2
Physics of Sound

• Sound is simply ENERGY
• Sound is a Pressure Wave
• Sound is rapid pressure variation above and below
  atmospheric pressure

3
Sound Frequency

• The rate of Vibration in air corresponds to the
  FREQUENCY of the sound and is expressed as cycles
  per second or Hz

4
Sound Pressure

• Low Frequency

• High Frequency

5
Loudness and Hearing

• The human ear is sensitive to a wide range of
  intensities.
• The threshold of hearing is the quietest sound
  the average human can hear at 1000 Hz. This is a
  sound intensity 10-12 W/m2 (or 0.000000000001 W/m2
  ).

6
Loudness and Hearing

• The threshold of pain is the intensity where we
  experience pain in our ears.
• This occurs at sound intensity of 1 W/m2.
• This range of intensities covers twelve orders of
  magnitude (decimal places)!
• To compress the loudness scale, we use a
  logarithmic unit called a decibel (dB).

7
Properties of Decibels

• By taking the logarithm, we get a much smaller
  range of sound levels.
• The threshold of hearing is 0 dB, and the
  threshold of pain is 120 dB.
• Compare that to 0.000000000001 W/m2 for the
  threshold of hearing and 1 W/m2 for the threshold
  of pain.

8
Properties of Decibels

• When you add 10 dB, the sound intensity increases
  by a factor of 10.
• 80 dB is 10 times more intense than 70 dB.
• 90 dB is 100 times (10 times 10) more intense
  than 70 dB

9
Properties of Decibels

• Increasing the sound level by 3 dB doubles the
  intensity.93 dB is twice as intense as 90 dB.
• Remember, OSHA uses a 5 dB doubling.

10
Sound

• SUPERSONIC Sounds Sound Pressure above the
  hearing threshold
• SUBSONIC Sounds Sound Pressures below the
  hearing threshold

Dog Whistle
11
Speed of Sound

• The speed of sound is ?
• Approximately 761 mph
• We consider aircraft to be supersonic if it
  exceeds 770 mph (greater than Mach 1)
• What occurs at Mach 1?

12
Sound

• Young, healthy individuals are capable of
  distinguishing sounds with the frequency range of
  between 20-20,000 Hz. Older people will lose
  their ability to hear this broad range.

13
Effects of Noise

• Interference with speech communication and other
  auditory signals.
• Annoyance and aversion.
• Noise-induced hearing loss.
• Changes in various body systems.
• Interference with sleep.

14
Speech Sound

• Sound Frequencies in the speech range are
  typically found between 250-3000 Hz. Hearing
  loss in this range is considered more critical
  because the result is a severe disability to
  distinguish verbal communication.

15
Sound Pressure Measurement

• Sound Pressure is typically measured with a Sound
  Pressure Level Meter (SLM)

16
SLM Weighting Network
17
Frequency Measurement
18
Employee Noise Dose Measurement
19
Variation in Decibel Levels

20
Hearing Loss

• Presbycusis hearing loss associated with aging
• Sociocusis hearing loss associated with social
  activities rock concerts and other loud music,
  activities not associated with work.
• Paracusis hearing sounds incorrectly

21
Factors Affecting Hearing Loss

• Sounds in the range 1000 Hz-5000 Hz, where the
  ear is most sensitive, are more likely to cause
  damage than other frequency sounds.
• Different individuals will have differing degrees
  of damage. Some factors that are important are
  age, gender, and genetic differences.

22
Audiometric Testing

• Baseline Audiograms
• Yearly Audiograms
• Hearing Threshold Level
• Audiometric Technician
• Audiometer

23
Noise-Induced Hearing Lossthe hearing loss
notch
24
Tinnitus

• Ringing, roaring, hissing sounds in the ears
• Often follows a trauma of loud noise
• May be permanent or may go away with time.
• Typically associated with a permanent hearing
  loss from noise.

25
Vibration

• Sound Pressures that are low often well below
  the threshold of hearing
• Creates 2 distinct disorders

26
Vibration

• A.     Obstruction of Blood Vessels - Hazards
  typically arise from using vibrating tools such
  as air hammers, air chisels, chain saws.
• B.     Dead Fingers or White Fingers
  (Raynauds Phenomenon). Occurs mainly in the
  hand used to guide the vibrating tool.

27
Acoustic Trauma

• Damage to the inner ear
• Typically caused by explosions, gun shots, blasts
  or other traumatic, sudden noise
• Not uncommon with demolition projects

28
Acoustic Trauma Hazards Building Implosion
29
OSHA Regulations

• 29 CFR 1910.95
• Permissible Exposure Limit (PEL) 90 dB(A)
• Action Level (AL) 85 dB(A)
• Hearing Conservation Program

30
Key Elements of a Hearing Conservation Program

• Noise Measurement (SLM, Noise Dosimetry)
• Acoustic Measurement (hearing testing)
• Use of Hearing Protection Devices (HPD)
• Written Program
• Employee Training
• Engineer-out the noise where possible

31
(No Transcript)
32
Quiz 2

• 1. We use decibels to describe sound because?
• A humans hearing range is so broad, it makes
  measurements and calculations easier
• Its the only readout we can get from a SLM
• OSHA dictated it
• MSHA dictated it

33
Quiz 2

• 2. Acoustic Trauma typically occurs from?
• Tinnitus
• Ear wax build-up
• The bones in the ear calcify
• A loud blast or explosion

34
Quiz 2

• 3. Presbycusis is?
• Hearing loss from rock concerts
• Hearing loss from noise
• Hearing loss from old age
• Hearing loss from birth defect

35
Quiz 2

• 4. Sound is?
• Pressure energy above and below the atmospheric
  pressure
• Unwanted noise
• Not measurable
• Not well understood

36
Quiz 2

• 5. Noise will adversely affect humans?
• Always the exact same way
• Will vary with sex, age and other individual
  characteristics
• Only if they are exposed to 90 dB(A) or more
• None of the above

37
Quiz 2

• 6. Vibration causes?
• Blue rings around the ears
• White finger or Dead finger disease
• Green warts on the ear lobes
• Yellow ear hair

38
Quiz 2

• 7. Noise may be measured by all but?
• Audiometer
• Sound Level Meter
• Noise Dosimeter
• Octave Band Analyzer

39
Quiz 2

• 8. Which is not true about Decibels?
• In sound physics there is a 3 dB doubling
• OSHA uses a 5 dB doubling
• Decibels were named after Alexander Graham Bell
• Decibels can be used to measure noise, but not
  sound

40
Quiz 2

• 9. Sociocusis is?
• Loss of hearing from work
• Loss of hearing from drugs
• Loss of hearing from social activities
• Loss of hearing from genetic disorders

41
Quiz 2

• 10. Which is true of Tinnitus?
• It never follows a hearing loss
• It is caused by smoking crack
• It is a ringing, roaring or hissing in the ears.
• Im not sure, this ringing in my ears wont let
  me concentrate