How We Hear

Our ears are not only part of the mechanism to help us to hear but also part of the balance system. The ear is split in to three sections: the outer, the middle and the inner ear.

The Outer Ear

The pinna collects sound and funnels it down the ear canal, also known as the external auditory meatus. The sound travels towards the tympanic membrane, also known as the eardrum. The eardrum vibrates and sends these vibrations into the middle ear. Any blockage or damage in this part of the hearing system would cause a conductive hearing loss.

The Middle Ear

The middle ear is an air-filled cavity about 1.3cm across. The eustachian tube, which runs down the side of the neck from the middle ear, connects it to the nose and throat.

When sound enters the ear canal it makes the eardrum vibrate. The vibrations affect the middle ear bones called the ossicles. The ossicles are a chain of three tiny bones – the malleus, incus and stapes – which in turn conduct sound through to the inner ear. Any blockage or damage in this part of the hearing system would cause a conductive hearing loss.

The Inner Ear

The inner ear comprises two parts: the cochlea (for hearing) and the semi-circular canals (for balance).

How we hear – The Cochlea

The cochlea is a coiled spiral tube about 3.5cm long, consisting of an outer and inner fluid-filled chamber. The inner chamber contains the organ of corti, which comprises 17,000 small hair cells. Each have tiny hair-like structures called stereocilia, which project into the cochlear fluid. As sound waves move through and enter the cochlea, the stereocilia move and so trigger an electrical pulse in the auditory nerve. The nerve passes electrical impulses to the brain, which then recognises those impulses and translates them into recognisable sounds. Any damage in this part of the hearing system would cause a sensorineural hearing loss.

How we hear – Semi-circular canals

Our hearing doesn’t use these, the balance system uses the semi-circular canals. They are filled with fluid and have hair cells that project stereocilia, rather like those in the cochlea but these give the brain information about which position and direction your head is in.

Hearing Loss

The most common cause of hearing loss is the ageing process also known as Presbyacusis. There are however a number of other factors such as wax build up, noise exposure, illness, accidents, medications and hereditary conditions that also cause hearing loss. If the damage or blockage is in the outer or middle ear then this is called a conductive hearing loss. If the damage is in the inner ear then this is called a sensorineural hearing loss.

Damaged Hair Cells

The degree of loss can range from mild to profound, depending on the degree and cause of hearing loss will depend on the impact that hearing loss is having on quality of life and hearing communication and also what the best intervention will be. It is vital that anyone having issues with hearing loss seeks early intervention.

How we hear -Tinnitus

Tinnitus is a relatively common condition affecting about 30% of the population at some point in their lives. It affects people differently, so it can be mildly annoying and intermittent for some, while for others it can seriously impact on their quality of life.

Tinnitus is the sensation of hearing a sound/s in the absence of any external source. The sounds heard can vary hugely although the most commonly reported are ringing, buzzing, whooshing or humming. It can be continuous or just come and go and for some people it seems like it is in one ear or both, in the middle of the head, or difficult to pinpoint.

It is more common in those who have a hearing loss or other ear related issues such as wax build up.