There are various types of hearing loss, classified on the basis of which part of the hearing pathway is affected. These different types of hearing loss are described below:
a. Conductive hearing loss:
Conductive hearing loss occurs as a result of any pathologic condition affecting the outer or middle ear, including the ear canal, tympanic membrane (ear drum), middle ear cavity, middle ear ossicles (bones) or Eustachian tube. Conductive hearing loss interferes with the transmission of sound through the outer and middle ear into the inner ear. Conductive hearing losses primarily reduce the loudness of an incoming signal.
b. Sensorineural hearing loss:
Sensorineural hearing loss refers to a hearing loss related to a problem affecting the inner ear, which includes the cochlea and the auditory nerve. Damage to cochlea as a result of damage to the hair cells or inner ear fluids can cause a disruption in the inner ear’s ability to convert sound vibrations into chemical signals transmitted to the auditory nerve. Dysfunction of the auditory nerve prevents effective transmission of electrical signals to higher-level auditory pathways. Sensorineural hearing losses usually result in both a reduction in speech detection and an inability to understand speech, particularly when it is presented in background noise or when visual cues are absent or reduced.
c. Mixed hearing loss:
Individuals presenting with mixed hearing losses have both a sensorineural and conductive component to the hearing loss in the affected ear.
d. Central hearing loss:
Central hearing loss refers to a condition in which the peripheral parts of the ear (including the outer, middle and inner ear) are working properly, yet the auditory cortex is not able to interpret sounds properly.
e. Auditory Neuropathy/Auditory Dys-synchrony:
Auditory neuropathy refers to a hearing disorder where sound enters the ear normally, but the transmission of signals from the inner ear to the brain is impaired. Individuals with auditory neuropathy present with speech perception that is far worse than what would be predicted by their hearing thresholds.