The ear

The ear (please see the diagram below) consists of three sections:

1) the outer ear, 2) the middle ear and 3) the inner ear.

The outer ear (a) consists of the auricle (the visible part of the ear on either side of the head) and the ear canals that go into the head. The auricles collect the sound waves and direct them through the ear canals to the tympanic membrane. The sound waves reaching the eardrum cause the tympanic membrane to vibrate sympathetically to the incoming signal. This vibration is passed on to the middle ear (b). In the middle ear, a small cavity in the mastoid bone, there are three tiny ossicles called malleus, incus and stapes. These bones amplify and conduct the vibrations of the eardrum to the inner ear. The inner ear (c) consists of an organ called the cochlea. The cochlea contains tiny hair cells which move in response to the vibrations passed from the ossicles. The movement of these hair cells generates electrical signals which are eventually transmitted to the brain through the auditory nerve where they are perceived as meaningful sound.


Hearing loss

Hearing loss can be classified into two basic categories called a) conductive and b) sensorineural When there are both, conductive and sensorineural elements in a hearing loss we use the term: mixed hearing loss.

a) Conductive hearing loss. Conductive hearing loss is caused by anything that interferes with the transmission of sound from the outer to the inner ear. Possible causes of conductive hearing loss are:

  • Middle ear infections
  • Collection of fluid in the middle ear
  • Blockage of the outer ear by wax or other foreign body
  • Damage to the eardrum by infection or injury
  • Otosclerosis etc

Conductive hearing loss is not severe and can be treated medically or surgically.

b) Sensorineural hearing loss. Sensorineural hearing loss is due to damage to the pathway for sound impulses from the hair cells of the inner ear to the auditory nerve and the brain. Possible causes are:

  • Hereditary
  • Presbyacusis i.e. the decline in hearing that many people experience as they get older
  • Viral infections of inner ear caused by viruses such as measles, mumps or meningitis
  • Acoustic trauma i.e. injury to the hair cells by loud noise
  • Menieres disease
  • Certain ototoxic drugs
  • Acoustic neuroma etc etc

Sensorineural hearing loss, is usually very severe and cannot be treated either medically or surgically.

Deafness in children

According to the available non-official statistical data of children born each year in the E.U. about 1,5 – 2,5% have moderate to severe sensorineural hearing loss. This is the result of problems associated with perinatal or prenatal complications or hereditary reasons, or problems during pregnancy. For example if a pregnant woman gets rubella, especially in the first three months of pregnancy, her baby is at the risk of being born with profound deafness, among other possible abnormalities.

Diagnosing hearing loss

Hearing loss may be a very slow gradual process as in presbyacusis, or it can be very sudden, as in some viral infection of the inner ear. If you , your friends or your family think that your hearing is deteriorating you should arrange to be seen by an ear, nose and throat (ENT) specialist also called an otolaryngologist.

In order to discover whether you have a hearing loss or not, you have to undergo some audiological testing, with various audiological equipment such as the audiometer, tympanometer, etc. The audiometer produces sounds of different intensities and frequencies. During the testing you are asked to respond when you hear a sound in headphones. The level at which you can just hear a sound of a certain frequency is known to be your threshold in that frequency. Usually the frequencies tested are: 250Hz, 500Hz, 1KHz, 2KHz, 4KHz, 6KHz, and 8KHz. The results are presented on a graph called audiogram. Hearing loss is measured in dBHL (decibel hearing loss).

A person who can hear sound across a range of frequencies at 0dB to 20dB is considered to have normal hearing. If you can hear sounds from 25-39dB you have a mild hearing loss. If you respond between 40-69dB then you are considered as having a moderate hearing loss. If you hear between 70-94dB then you have a severe hearing loss. If you respond only above 95dB, then you have a profound hearing loss.

Treating hearing loss

The treatment of hearing loss depends on the cause. If the hearing loss is conductive in origin then it can be cured medically or surgically. On the contrary, if the hearing loss is classified as sensorineural then, unfortunately, there is no cure, either medical or surgical. The only solution to the problem is hearing aids. There are many different types of hearing aids available today and the audiologist will advise as to which type, analogue or digital best suits your needs. When hearing aids do not give sufficient amplification, as with profound hearing loss, then a cochlear implant may be the solution.