Hearing is one of the five basic human senses. Hearing is a complicated process that we use daily without really thinking about it. Still, it is good to reflect for a moment on how miraculously hearing actually works. In this blog post, we highlight the anatomy of the ear and explain how the different parts work together to enable us to hear. You can also read about how hearing can be damaged and what types of hearing loss there are.
What are sounds?
Sound is usually defined as audible changes in air pressure. These changes manifest themselves in a wave motion. Humans (and most animal species) perceive sound when a sound wave reaches the ear. The vibrations are picked up and transmitted to the eardrum, which vibrates at the frequency of the sound wave. The vibrations are then transmitted as signals to the brain. There, the signals are interpreted so you understand what it is that you are hearing. All this happens in a split second.
Vibrations can be detected through the ear as well as through other parts of the body, such as the skull or bone tissue. This is called bone conduction: sound waves reach the inner ear via vibrations in the bone, without passing through the ear canal. Although the attenuation is great when wearing earplugs, it is still possible to perceive sound while wearing earplugs.
By the way, sounds can also occur in a medium other than air, such as water. A technically correct definition of sound would therefore be: noticeable changes in the density of a medium.
Parts of the ear
How hearing works is easier to understand if you are familiar with the basics of ear anatomy. Our auditory system consists of several parts. In order to hear sounds, many parts of the ear must function correctly and work together.
Outer ear
The outer ear consists of the auricle (pinna) and the external auditory canal (meatus acusticus externa). The anatomy of the auricle may seem complicated. But this visible part of your ear consists almost exclusively of flexible cartilage and skin. It acts as a kind of inverted megaphone.
Middle ear
The middle ear consists of the eardrum (membrana tympani) with the tympanic cavity behind it. The tympanic cavity contains three small ossicles (ossicula auditus). These are the hammer (malleus), the anvil (incus) and the stirrup (stapes). The stirrup is the smallest bone in your body. It is even smaller than a grain of rice! Small muscles are also attached to the ossicles.
Inner ear: cochlea and balance organ
The inner ear contains the cochlea. On the inside of the cochlea, which is filled with fluid, are thousands of tiny cilia. These, in turn, are in contact with nerve fibres, which form the auditory nerve (nervus cochlearis). This runs from the cochlea to the first 'station' of the central nervous system: the brainstem (nucleus).
The auditory nerve is also connected to the labyrinth, which contains the balance organ. You do not need this to hear. But the fact that the labyrinth connects directly to the auditory nerve explains why people with severe hearing damage sometimes suffer from dizziness and other balance complaints.
How hearing works
You are now familiar with the basic anatomy of the ear. But how exactly does the ear work? The parts we described above together form the auditory system. This works constantly. The job of the auditory system is to convert sound waves into nerve impulses, which can then be interpreted by the brain. That process runs as follows:
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Sound vibrations are picked up by the auricle and transmitted to the external ear canal.
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The sound vibrations reach the inner ear, causing the eardrum to vibrate.
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The vibrations of the eardrum also cause the ossicles to move; first the hammer and anvil, and then the stirrup. This then taps against the oval window covering the entrance to the cochlea.
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The tapping of the stirrup against the oval window causes the fluid in the cochlea to move. The liquid acts as a conductor, causing the thousands of tiny hair cells to move as well.
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The vibrations are then transported to the brainstem via the auditory nerve. From there, neural impulses travel to the brain, which gives meaning to the sounds.
Hearing loss
Hearing loss can have a variety of causes. Depending on the cause, different parts of the ear may be affected.
What are the causes of hearing loss?
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Exposure to loud noises
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Old age (presbycusis)
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Head injury
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Obstructions
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Bacterial or viral infections
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Medical conditions (such as otosclerosis or Ménière's disease)
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Neurological problems
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Use of certain medications
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Heredity
What types of hearing loss are there?
We distinguish different forms of hearing loss:
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Perceptive hearing loss
Perceptive hearing loss is the most common type. In this type of hearing loss, the hair cells in the cochlea or the auditory nerve itself are damaged. This is often the result of repeated and/or prolonged exposure to loud noises. But it can also be the result of a medical condition, head injury or simply old age. The auditory nerve and cilia in the ear do not repair themselves. It is also not possible to repair them through medication or surgery. The damage is therefore permanent. With a cochlear implant, for example, people with sensorineural hearing loss can perceive some sound again. However, the sound is then very flat - you would never be able to hear all the tones as you did before.
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Conductive hearing loss
Conductive hearing loss, also called conduction deafness, occurs when sound vibrations do not reach the inner ear. The cause is in the outer or middle ear. This may involve damage, inflammation or obstruction. Obstructions can range from earwax or fluid to a tumour. Conductive hearing loss is, however, most common in young children who have had a foreign object pushed into their ear or suffer from recurrent ear infections. Some birth defects can also cause conductive hearing loss.
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Mixed hearing loss
Mixed hearing loss involves a combination of sensorineural and conductive hearing loss. This involves damage to parts of the outer or middle ear as well as the inner ear. If you have mixed hearing loss, you usually hear sounds only very faintly. It can be particularly difficult to understand speech, especially in situations with other ambient sounds.
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Neural hearing loss
We speak of neural or retrocochlear hearing loss when the cause is behind the cochlea - that is, in the auditory nerve, the brainstem or the brain itself. This type of hearing loss cannot be remedied with a hearing aid or cochlear implant. After all, the auditory nerve cannot transmit signals to the brain. In some cases, however, an auditory brainstem implant can be placed. This bypasses the cochlea and auditory nerve to directly stimulate the auditory nerve pathways.
Take care of your ears and protect them with proper hearing protection
Hearing damage caused by exposure to loud noises is permanent and irreparable. So take good care of your ears. Pay attention to ear care. Alpine has the right hearing protection for every situation.!
This article is for informational purposes only and does not replace medical advice. Have questions about your health? Contact a doctor or healthcare provider.
