What is Hearing Loss?

Image of the man

Sound travels down the ear canal and vibrates the eardrum. Connected to the eardrum are the three smallest bones in the body: the malleus, incus and stapes (ossicular chain). The three bones work together to transmit the sound to a fluid filled organ called the cochlea. Inside the cochlea are millions of tiny hair cells which are connected to the 8th cranial nerve (the nerve of hearing). These tiny hair cells are stimulated as the sound wave vibrates the fluid in the cochlea. The nerve then takes the signal to the hearing center of the brain. Hearing loss can occur at any point in the hearing process. Hearing loss is generally characterized by the type of loss and the degree of loss.

 

Anatomy of the Ear

Image of the Ear 1. The Outer Ear. Includes the Pinna and the Ear Canal.
A.The Pinna.
B.The Ear Canal, the tube leading to the Middle Ear where ear wax is produced.
2.The Middle Ear. Includes the Eardrum and the Ossicles or "middle ear bones".
C."Tympanic Membrane" or Eardrum.
D. Incus also called the "hammer" is connected to the ear drum.
E.Malleus or "anvil."
F.Stapes or "stirrup."
3.The Inner Ear. Includes the cochlear and semicircular canals.
G. The Cochea. Converts sound vibrations to nerve impulses.
I.The Eustachian. Regulates the pressure between the middle ear and the atmosphere.


Type of hearing Loss
There are three types of hearing loss:

Conductive

This type of loss is due to a problem somewhere within the middle ear which consists of the ear canal, the eardrum, the middle ear cavity and the ossicles (three tiny ear bones). Conductive hearing loss occurs when something keeps the sound from reaching the nerve. This can include, but is not limited to; ear wax in the ear canal, a perforated eardrum, fluid behind the eardrum, and/or a disruption in the ossiclar (bones) chain. Conductive hearing loss in most often temporary and can usually be treated by a physician. An audiological exam is essential to determine the correct course of treatment. When the loss can not be treated by medicine or surgery, hearing aids may be recommended. This is the most common hearing loss found in children. Symptoms of conductive hearing loss: Ear pain, drainage, plugged feeling, popping or crackling and/or decreased hearing following an ear infection or cold.

Sensorineural

Sensorineural hearing loss, or nerve damage is the most common form of hearing loss. It generally happens gradually and is usually permanent. The usual treatment for this type of hearing loss is hearing aids. This is the most common hearing loss found in adults, especially those who have been exposed to loud sounds.

Mixed

Patients with mixed hearing loss have both a conductive component and damage to the nerve.

 

Degrees of hearing loss

A hearing test checks hearing sensitivity at a number of select frequencies”250Hz to 8KHz”. The degree of hearing loss can vary at the individual frequencies. For instance, a patient may have normal hearing and the low frequency region and a severe hearing loss in the high frequency region Hearing Loss is Categorized into the Following Levels:

  • Normal Hearing: 0 to 25 dB for adults and 0 to 20 dB for children
  • Mild: 30 to 40 dB for adults and 25 to 40 dB for children
  • Moderate: 45 to 55 dB
  • Moderately-Severe: 60 to 70 dB
  • Severe: 75 to 90 dB
  • Profound: 95 dB or greater