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Know your Hearing

Today a major part of our population suffers from hearing loss; Reasons are many! Environment, eating habits, unhealthy regimes, infections, injury etc. A survey indicated as high as 1in every 10 individuals in our country suffers from some or the other kind of hearing problem! This is huge.

In order to understand the loss of hearing, we must know what human hearing is and how it is regulated. Below is an image depicting the physiology of hearing:

Ear works as a transmitter of acoustic energy to the brain. For hearing to take place, there is a 3 level conversion of energy within the ear before the signal reaches the brain and is interpreted as speech.

The outer structure of the Ear called the Pinna receives the sound as acoustic energy which is funnelled inside the ear canal.

At the end of the canal is the ear drum or tympanic membrane attached to which are three of the smallest bones in our body called malleus, incus & stapes. This part of the ear is called the middle ear and it is here that the acoustic energy is converted to mechanical energy as these bones vibrate.

The vibrations are then sent to the inner part of the ear where there is an organ called the Cochlea. Within the cochlea are numerous hair cells and fluid which convert this mechanical energy to electromagnetic impulses. These impulses are sent to the brain where they are de-coded and understood as speech.



Types of hearing Loss

Hearing loss can occur due to defect in any of the 3 parts of the ear i.e. outer ear, middle ear & inner Ear or all together.

Following are some of the problems which exist in correspondence to the defects of the outer ear:

Microtia: This is one of the congenital defects which occurs due to underdevelopment of the outer ear or the pinna. These cases require surgery which involves pinna development. There may be cases where pinna is not there but ear canal is good. These cases can use the help of CIC hearing aids in case of a hearing loss.
Swimmers ear: is a type of outer ear/ear canal infection also known as otitis externa. This is caused due to negligence of hygiene and bacterial growth especially found in swimmers due to exposure to dirty water.

Following are some of the problems associated with the Middle ear:

Middle Ear Infections: otitis Media is a typical type of middle ear infection which leads to a swollen ear drum accompanied by severe pain. This can cause a lot of irritability especially in infants and can be accompanied by respiratory track infection, nasal discharges and cough.
Otosclerosis: If there is a abnormal bone growth near the middle ear, it leads to otosclerosis. Otosclerosis is known to cause a large number of hearing losses in population where the hearing loss can be conductive as well as sensorineural In nature in some cases.
Perforation of Ear Drum: Due to injure or CSOM, there can be a perforation of the tympanic membrane or the ear drum leading to discharge from the ear due to build up of negative pressure in the middle ear. This condition can cause a conductive hearing loss which if ignored can lead to a mixed hearing loss in future.

Following are some of the conditions associated with hearing loss originating from the inner ear:

Presbycusis: This is a typical age related hearing loss which occurs due to de generation of the hair cells in the cochlea. This type of hearing loss is very common in geriatric population especially people above 60 years of age.
NIHL: NIHL or noise induced hearing loss is a result of oxidative cell death within the cochlea due to over exposure to acoustic energy or Noise. Since the outer hair cells of the cochlea also responsible for determining the high frequency sounds are the first to get in contact to the vibration, these are to first set of hair cells to get damaged causing a high frequency hearing loss to the individual.
Please visit our page on ear protection devices to gather more information on the tolerance of human ear and ear protection options for NIHL.
Retro cochlear pathology Any disorder/pathology related to the auditory nerve is called a retrocochlear pathology. This can include auditory neuropathy, CAPD, Tumor etc. These issues have to be diagnosed by the ENT consultant after being reviewed by Audiologist & Neurologist in some cases.

How Does a hearing aid work?
Hearing aids are electro acoustic devices that provide necessary amplification to the individual basis his hearing loss. Hearing aids consist of Microphone, receiver, microchip for signal processing and a receiver which delivers the amplified sound to the ear.

There are 2 types of hearing aids namely: Digital Hearing Aids and Analog Hearing Aids. These two differ in terms of sound processing, amplification and comfort to the user.
Following are some of the differences between analog & digital hearing aids:

Analog Hearing Aids Digital Hearing Aids
Analog Hearing Aids Linearly amplify all sounds which they receive and transmit to the Ear Digital Hearing Aids Amplify the sound in a non-linear way utilizing sound compression to reduce the pinch of the loudness
Analog Hearing Aids Process all Sound Signals alike Digital Hearing Aids maintain a Signal to Noise ratio wherein they can filter out noise from the sound signals to an extent to provide clarity of speech to the user.
These hearing aids are useful in cases where more amplification is required for the user especially in case of profound losses and where there are dead regions in a cochlea These hearing aids are more comfortable as speech is more clear and the sound is not annoyingly amplified
These hearing aids cannot be tuned to a patients hearing loss and only come with a gain adjustment feature These hearing aids can be tuned correctly to the patients hearing loss thereby providing more clarity & comfort
This can at times damage the hair cells due to excessive sound & noise The noise and sound can be controlled in digital hearing aids hence making them good stimulants for hearing.

Hearing aids are rehabilitative or alternative treatments and apply especially in case there is a sensorineural hearing loss. Correctly using a hearing aid can not only maintain the discrimination ability due to proper stimulation but can also help keep the hearing system healthy in the long run.