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Type , Degree and Cause of Loss

1. Conductive hearing loss

This type of hearing loss is a condition of the outer and/or middle ear. It occurs when sounds from the outside cannot be transmitted normally through the ear canal and/or middle ear to the inner ear.

Some possible causes are:

  1. Build-up of wax in the ear canal
  2. Foreign bodies
  3. Infection of the external auditory canal
  4. Perforated eardrum
  5. Middle ear infection (common in children)
  6. Damaged or defective middle ear bones
  7. Otosclerosis

Build-up of wax in the ear canal

TypeofLoss01

Middle ear infection

TypeofLoss02

Perforated eardrum

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2. Sensorineural hearing loss

This happens when the hair cellsand/or the delicate auditory nerves in the inner ear are damaged. When this occurs, auditory nervies are unable to convert or transmit sound signals to the brain.

Some possible causes are:

  1. Aging
  2. Excessive exposure to loud noise (e.g. working in noisy environments for a long time)
  3. Acoustic trauma (injury caused by loud noise)
  4. Head trauma
  5. Intake of ototoxic drugs
  6. Family history of hearing loss
  7. Acoustic neuroma
  8. Viral infection e.g. measles, mumps
  9. Congenital infection e.g. rubella
  10. Meningitis
  11. Meniere’s disease

Normal Hair Cell in Cochlea

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Damaged Hair Cell in Cochlea

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Mixed hearing loss

This kind of hearing loss is caused by a combination of problems in the middle and the inner ear.

This refers to the severity of the loss. The numbers represents individual’s hearing thresholds, or the softest intensity at which a sound is perceived. The following is one of the more commonly used classification systems:

Audiogram_2

Mild hearing loss (26-40 dB): Unable to hear soft sounds, difficulty understanding speech clearly in noisy environments.
Moderate hearing loss (41-55 dB): Unable to hear soft and moderately loud sounds, considerably difficult understanding speech, particularly with background noise.
Moderately severe hearing loss (56-70 dB): Increasing difficulty in hearing and speech understanding, yet communication can be improved with the use of hearing instruments.
Severe hearing loss (71-90 dB): Some loud sounds are audible but communication without hearing instrument is impossible.
Profound hearing loss (91 dB+): Some extremely loud sounds are audible but communication without a hearing instrument is impossible.