Hearing Conservation Training program

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Hearing Conservation Training program

• Dr Mohamad Sabri Mohd Shaffi

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CONTENTS

• Principle of sound and hearing mechanism.
• Effect of noise on human
• Law related to Hearing Protection
• Audiometric Test
• Hearing Protective Devices

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sound

• The changes of pressure in a specific medium
  which is detected by the ears
• Sound waves cannot pass through vacuum.

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Definition

• HERTZ ( Hz ) unit for frequency
  Bass 500 Hz Treble 3000
  Hz Human hearing Frequency
  20-16000Hz Human speech /
  communication 300 - 3000 Hz
• DECIBEL ( dBA ) measurement of intensity 0 dBA
  lowest intensity heard
  140 dBA Threshold of pain

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Principle of Sound

• The sound energy is produce by vibration of the
  medium
• Moves through a medium and can be heard
• The speed and distance depend on the density of
  medium
• Sound cannot pass through vacuum
• Various speed through a medium a. Air
  - 340 meter per second. b. Water -
  1500 meter per second. c. Metal - 5000
  meter per second.

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NOISE

• THE UNWANTED SOUND

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HEARING ORGAN MECHANISM

• Structure of the ear a. Outer ear b.
  Middle ear c. Inner ear
• Parts of the ear Outer ear
  Pinna, Auditory canal Middle ear
  Ossicle bone Eustachian tube Inner ear Oval
  window, semicircular canal, cochlea
  auditory nerves.

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STRUCTURE OF THE EAR
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THE EFFECT OF NOISE...

• Classification of sound according to the
  frequency - i. Infrasonic ( 0 - 20 Hz
  ) ii. Human ability to hear ( 20 - 16000 Hz
  ) iii. Ultrasonic ( more than 16000 Hz
  )
• Speech/communication ( 300 - 3000 Hz )
• Noise spectrum ( Figure 1 )
• The factors that influence the effect of noise
  on human ......

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4 factors influence the effect of noise to human.

• The frequency of noise Higher frequency is
  more dangerous than lower frequency
• Noise intensity Higher intensity is
  more destructive than the lower
  one.
• Duration of exposure The longer the
  duration the more the risk (
  DOS )
• Individual Susceptibility Different individual
  has different susceptibility to
  noise

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The effect of noise

• On hearing.
• On the body.
• At work.
• Psychological aspects
• Other effects acccording to scientific
  research.

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Effect to the Ear

• Causing Tinnitus
• Loss of hearing eventually deafness
• Destruction of tympanic Membrane or
  Dislocation of ossicles due to loud noise.

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Effect to the body

• Increases the heart rate and rate of respiration.
• Increases the gut motility ,blood pressure,
  glucose and lipid level.
• Cause lethargic, giddiness and headache.
• Cause gastric ulcers

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Psychological Effect

• Stress
• Emotional Disturbance ( Bad Tempered )
• Loss of concentration.
• Sleep disturbance

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Effects at Work

• Reduced Efficiency.
• Reduced Productivity.
• Communication disturbance.
• Hearing Incapability may lead to ...
• Accidents.!..

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Noise induced hearing loss (NIHL )....

• Temporary Loss - - After
  exposure to loud noise
  - Return to normal after 14 - 16 hrs
  noise free period.
  
• Permanent Loss -
  - If continously exposed to noise.
  - Stimulus to
  the Cochlea ( Organ of Corti )
  - Permanent Damage to hair cells
  - Irreversible destruction to hair
  cells and nerves
  
  
  
  

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Hearing Loss

• CONDUCTIVE
• Changes to - - Outer ear
  - Middle ear
  
  
• Due to - - Blockage to auditory canal
  - Ear drum changes - Changes to
  ossicles - Changes to middle
  ear

• SENSORINEURAL
• Changes to - - Hair cells
  - 8th Cranial Nerves
• Due to - - Noise
  - Ototoxic drugs - Chemical
  - Degenerative diseases