Hearing Tests

This is a section about "How We Hear and Hearing Tests". For information on hearing aids, please click here.

How We Hear:

The ears are responsible for hearing and balance. They are divided into three different sections, the Outer, Middle and the Inner ear.

The outer ear is responsible for directing sound in your ear canal and gives a sense of direction to you..

Middle ear: Is an air filled narrow space connected with the back of ones throat by a small tube called the Eustachian tube. There are three tiny bones which stretch from the eardrum to the inner ear and are responsible for transmitting sound from the former to the latter.

Inner ear: has two parts, the cochlea, for hearing and the vestibule for balance. Cochlea is a spiral snail like tube and has thousands of hair cells along the length of the cochlea. These hair cells are connected to the auditory nerve (the nerve of hearing) which takes signals from the cochlea to the brain.
When sound is picked from the outer ear and passed to the middle ear and then to the cochlea, the hair cells trigger an electronic impulse that is transmitted to the brain by the hearing nerve. The brain understands as sound like an alarm clock ringing or somebody calling your name.

What Can Go Wrong:

When things go wrong with the hearing pathway, the obvious manifestation is a decreased responsiveness to sound, which we in laymen terms call deafness. There are two kinds of deafness:
  • Conductive deafness: When sounds cannot freely pass through the outer and middle ear.
  • Sensorineural deafness: When deafness is due to a problem in the cochlea or the hearing nerve, or both. Some people may also call this type of deafness as Nerve deafness, Sensory, Cochlear or Inner ear deafness.

Conductive deafness:

  • Otitis Media: This is an infection or inflammation of the middle ear. When this happens the middle ear may get filled with thick fluid, and the condition is called glue ear. The pressure changes in the ear need to be monitored by Tympanometry. 
  • Perforated eardrums: can be caused by ear trauma, poking things in your ear, head injuries, explosions or by untreated otitis media. They can heal by themselves in early stages but sometimes become permanent causing repeated infections and ear discharge.
  • Otosclerosis: this affects more women than men and can run in families. It is more common around the age of thirty and is caused by a bony overgrowth of the stapes because of which sound vibrations cannot pass freely through the middle ear to the cochlea. 
  • Damaged ossicles: the tiny bones in the middle ear can have serious infections or head injuries could damage them. Sometimes babies are born with bones that are improperly formed. 

Sensorineural deafness:

Most common cause of this is the damage to tiny hair cells in the cochlea. These hair cells cannot be replaced and therefore the loss is permanent. The damage can happen:
  • Due to old age. This is a natural process and is called presbyacusis.
  • Long term exposure to loud noise, example in factory workers, or people who listen to loud music all the time.
  • An affect of certain strong drugs.
  • Serious head injury.
  • Disease such as mumps or meningitis.
  • Infection to the pregnant mother, where the baby can be affected.
  • Genetic

Hearing Tests:

Hearing tests can be broadly defined as subjective and objective. In subjective tests the patient is required to give responses regarding the hearing.

Objective tests are those in which we can obtain responses by electrophysiology, or other such techniques.

a) Pure tone audiometry: This test aims at recording hearing threshold of a person by administering beep/ warble tones at various frequencies and intensities

b) Immittance Testing: Impedance and Admittance with middle ear Stapedial reflex. This tests the status of the ear drum and the muscle, bone and nerve system behind it.

c) OAE: Otoacoustic Emission testing gives us the status of the cochlear hair cells that are so important in transmitting sound to the hearing nerve.

d) ABR (BERA): Auditory Brainstem Responses is a test to monitor for hearing loss or deafness, especially notable for its use with newborn infants. It is a method employed to assess the functions of the ears, cranial nerves, and various brain functions of the lower part of the auditory system.

e) ASSR: Auditory steady state response is used to assess graphically represented hearing threshold levels in infants and children with severe-to-profound hearing impairment (i. e., cochlear implant candidates).

f) Behaviour Audiometry: Based on the child's age various conditioned games can be played to obtain an effectively useful estimate of the child's hearing loss.

Based on your hearing tests, you may be a suitable candidate for a surgery or a hearing amplification device.