A disease or disorder can affect the hearing sense and cause hearing impairment. Head injuries can also cause hearing impairment. The ear comprises outer ear, middle ear and inner ear. The visible part is the outer ear. The ossicles, which are small bones, form the middle ear. The inner ear consists of cochlea and auditory nerve.
The cochlea has hair cells which move according to the vibrations passed on from the middle ear. This movement produces electrical signal. The auditory nerve communicates this signal to the brain.
Conductive hearing loss and sensorineural hearing loss are the two types of hearing impairment. If there is interference to the transmission of sound to the inner ear, it causes conductive hearing loss. If there is problem in the inner ear or in the pathway to the brain from there, it causes sesorineural hearing loss.
What are the types of deafness
Mild deafness is a condition, which supports hearing of only 25 to 39 decibels. In noisy areas, you may not be able hear a speech properly.
Moderate deafness is a condition, which supports hearing of only 40 to 69 decibels. You may not be able to grasp a speech without a hearing aid.
Severe deafness allows hearing of only 70 to 94 decibels. In this condition, even a hearing aid may not be helpful, and you may to understand a speech only from lip movements and/or other body languages.
Profound deafness is a most severe condition, in which only sounds above 95 decibels may audible. People having this deafness can only depend on lip movements and associated body languages, to understand a speech.
When hearing loss can occur
Hearing loss can be congenital too. Newborns can have it, or they may develop when they grow. Therefore, it can affect in the childhood or in the adulthood. We can say that someone is deafened, if that person had no deafness at the birth, but developed severe or profound deafness after learning to speak. The severity of deafness increases with age.
What are the causes of hearing impairment
Causes of conductive hearing loss include the following:
- Infections in the middle ear
- Accumulation of fluid in the middle ear
- Earwax blocking the ear canal
- Damage to the eardrum
- Middle ear disorders
- Rheumatoid arthritis
Causes of sensorineural hearing loss include the following:
- Older age
- Hearing loud noises
- Mumps or measles
- Auditory nerve infected with virus
- Meniere’s disease
- A benign growth near auditory nerve
- Meningitis or Encephalitis
- Tumour in the brain or stroke
- Multiple sclerosis
A hearing impairment may have the cause of both the conductive and sensorineural hearing loss. Most commonly, age is the cause of hearing impairment. Between 30 and 40 years of age, many people lose hearing to some extent. This increase when they become older, and around 80 years, the loss becomes very significant. The next common cause is exposure to loud noises. The hearing loss due to this cause is known as acoustic trauma. The severity of this deafness depends on the period of exposure to the loud noises and the loudness of the noise.