The ear made up three sections : -
The outer ear consists of the pinna and the ear canal. The pinna is your external ear, which captures sound and funnels it into the ear canal.
The middle ear consists of the ear drum membrane and an air-killed cavity containing three small bones called ossicles. The individual ossicles are the hammer (malleus), anvil (incus) and stirrup (stapes) – and they vibrate together when the ear drum moves.
The inner ear consists of a complicated series of channels and chambers. For hearing, the important organ is the spiral shaped cochlea. Roughly the size of a pea, the cochlea contains fluid and about 15,000 tiny hair cells. Each hair cell is connected to the auditory nerve.
Hearing is the sense by which sound is perceived. Our brains differentiate between sounds by recognising differences in volume (intensity) and pitch (frequency). As we develop from infanthood, we are constantly listening to sounds and speech around us. As our brains begin to attach meaning to sound we learn to recognise sounds and voices and then learn to understand the meaning of words and speech. After much listening, we begin to learn to speak. In this way, hearing is necessary for the normal development of spoken language which is an essential part of communication.
How do we hear
In order to hear normally, a complete and clear signal must be transmitted to the brain from the external environment via the outer ear, middle ear, inner ear and hearing nerve.
Sound is gathered by the outer ear and sent down the ear canal to the eardrum. The sound causes the eardrum to vibrate which sets the three tiny bones in the middle ear into motion. The motion of the bones causes the fluid in the inner ear to move. The movement of the inner ear fluid causes the hair cells in the cochlea to bend. The hair cells proceed to change the movement into electrical pulses. These electrical impulses are transmitted to the hearing (auditory) nerve and up to the brain, where they are interpreted as sound.
ABOUT HEARING LOSS
Any damage or defect to the anatomy or physiology of the auditory system results in the ear not getting a clear or complete signal - That is a Hearing Loss.
Different types of hearing loss
There are three basic types of hearing loss -
SENSORINEURAL HEARING LOSS
Sensorineural hearing loss is often called ‘nerve deafness’. It is caused by damage to the cochlea, or the nerve pathways between the cochlea and the brain. Sensorineural hearing loss can be mild, moderate, severe, or profound. It can affect one or both ears, and is usually permanent.
CONDUCTIVE HEARING LOSS
Conductive hearing loss occurs when there is a problem with the outer or middle ear. This means that sound is unable to travel or ‘conduct’ from the outer ear to the eardrum and tiny bones, or ossicles, of the middle ear. A conductive hearing loss may occur in both ears or just one and can often be helped by medical or surgical treatment.
Conductive hearing loss can be caused by :
· Excess wax or a foreign object in the ear canal
· Outer ear infection
· Chronic ‘glue ear’ or middle ear infection, called otitis media.
· A hole in the eardrum (perforation)
MIXED HEARING LOSS
Mixed hearing loss combines problems with the conductive pathway (outer and middle ear) and the cochlea or auditory nerve (the inner ear). Mixed hearing loss can occur in both ears, or just one.
An audiogram is a means of recording the results of a hearing test. It will include a table and a graph for each ear showing how well you could hear sounds at various frequencies. This graph dominates the audiogram and measures the lowest volume that you can hear pure tone signals at different frequencies for each ear.
It may also record results of other tests that indicate how well various parts of your "hearing system" are working. For example, it may include:
· Your ability to recognize words.
· Your ability to understand words in context.
· Your ability to hear in noisy situations.
· Your auditory brainstem response.