Our body is incredibly adaptable. We can repair ourselves, fend off diseases, filter out dirty air, cool ourselves when we overheat, and warm ourselves up when we’re too cold. We have impeccable senses which help us navigate the world around us, and most of them we tend to take for granted.
For example, did you know that the nose can detect one trillion smells? Or that the human eye can recognise candlelight from over 20 kilometres away? Of course, that’s under perfect conditions; regardless, this is still an impressive feat. Our senses feed data to our brain and help us to perceive what’s going on around us.
Our bodies are no doubt the most complex network of systems known to date. Every part of our body needs to work together in order to function. Likewise, the way our ears work and the process of hearing is quite complicated. However, it is important for everyone to know the basics of how our body works to be able to make informed decisions on our health and lifestyle. Here is a simplified guide into understanding how hearing works, the factors that affect your hearing and steps you can take to maintain good ear health.
The very design of our ear assists with the passage of sound into the ear, which lets us distinguish where noises around us are coming from, and what they are. Essentially, the ear is made up of three parts or areas: the outer ear, the middle ear, and the inner ear.
The outer ear is made of parts that are actually visible to us. The outer ear contains the earlobe and the pinna, a protruding skin-covered flap made of cartilage. Despite being an odd-looking part of the body, the outer ear is responsible for a very important function – collecting sound waves and channelling them towards your ear. They are also shaped to partially block sound from behind you so that you can establish the source of the sound. In fact, the head acts as a sound barrier to each ear to help us localise a source of the sound. For example, if a source of noise is located to our left, our right ear will not hear this sound as clearly; and our brains notice that. Our brains are sensitive to these cues so that we can determine where to look and direct our attention. Unfortunately, without hearing in both ears, it’s hard for us to localise sound. For those with hearing loss in one ear, it’s best to get a hearing aid that works to amplify the sound in the affected ear.
Then, there’s the ear canal. The ear canal is a short (about 3cm) ‘S’ shaped passage that extends into the ear. The ear canal is lined with skin and fine hairs. The skin in our ear canal releases secretions that mix with dead skin and air particles to form a substance called cerumen, or earwax. The earwax and fine hairs work to guard the inner ear by catching dust and air particles that can damage the eardrum. Earwax is definitely necessary for our ears to function, but too much can also be problematic. An overload of earwax can block the ear canal and disrupt hearing, so remember to clean them out properly every now and again. More on this further down!
The middle ear is where you’ll find the eardrum, or more officially, the tympanic membrane. The middle ear functions to transfer vibrations converted from sound waves into the inner ear. This is done by three tiny bones (the tiniest bones in the human body, in fact), called the auditory ossicles, which collect the vibrations and amplify them. They are known as the Malleus, Incus and Stapes (or the Hammer, Anvil and Stirrup). Not only can these incredibly small bones amplify sound, but they can reduce sound to protect the inner ear and your hearing. Muscles in your brain signal surrounding muscles to adjust the performance of the ossicles. The eardrum is only 1cm in total and is a slightly curved shape. The lining contains many nerve endings making it extremely sensitive to pain. It’s also sensitive to ear pressure – the membrane needs steady pressure on both eardrums to hear clearly. The pressure is sensed through an auditory tube contained outside the eardrum. On an interesting note, the auditory tube is usually flattened to stabilise air pressure, but chewing, yawning or swallowing opens the auditory tube. When there is a disruption in ear pressure among both ears, this helps them reach an equilibrium. If there is a great disbalance, this can sometimes result in us hearing a ‘pop’.
The vibrations that pass through the eardrum and become amplified by the ossicles are then exerted onto the oval window, an opening covered by a thin membrane. As the oval window vibrates, this transfers into waves in the inner ear fluid.
The inner ear is the innermost part of the ear. This area contains the bony labyrinth and the membranous labyrinth. These systems contain a range of passages, canals and cavities which eventually turn sound waves into electrical impulses. The cochlear, in fact, is responsible for this process. The cochlear is a spiral-shaped bony canal (almost resembling a snail shell) that is filled with a fluid called perilymph and is located behind the oval window. The pressure in the cochlear causes the basilar membrane (located inside the cochlear) to vibrate, which forces small hairs inside the organ called the corti (another part of the basilar membrane) to vibrate. Depending on which place within the basilar membrane these hairs vibrate, the pitch we hear is determined. Serving as the body’s ‘microphone’, the loudness of the sound is also determined. It’s these hairs that send electrical pulses to the brain for processing, which is the final step towards us hearing sound.
If you’re interested and want to learn more, check out this Ted X video by Douglas L. Oliver on the ‘Science of Hearing’.
Hearing is one of those senses that we don’t value until it’s beginning to deteriorate or completely gone. Whilst it’s hard to imagine life without your favourite song, or without the voices of those you love, or without those pesky crows that caw way too loudly while you’re trying to do some work, this is the reality for many. So, how does this happen?
There are a number of factors that lead to hearing loss, the most prevalent of which is the natural aging process. In their 2017 report, the Hearing Care Industry Association (HCIA) found that the rate of hearing loss increases with age, particularly with men. Australian men over the age of 65 are expected to develop mild hearing loss and most women by age 90. Apart from age, other factors that may cause hearing loss include the following:
Ultimately, the causes of hearing loss can vary significantly, depending on the person. Hearing loss may be congenital (present at birth) or acquired. Some people can develop hearing loss over time progressively, and some suddenly. It can be temporary or permanent. Each individual is different.
Although there are many ways one might develop hearing loss, there are also great tips on how to prevent it. After all, we all want our ears to function well into our future years.
HCIA finds that almost half (49%) of childhood hearing loss is preventable, as is over a third (37%) of adult hearing loss. Hearing loss might not be reversible. It’s important to look after your hearing while you can.
Such preventable hearing loss cases are caused by meningitis, rubella, ear infections and glue ear. These cases can be prevented through good hygiene and, in some cases, vaccinations. For adults, the leading preventable cause of hearing loss is noise exposure.
To ensure you keep your ears protected from damage, follow these important steps.
Like any of your other senses, hearing plays a vital role in your perception and experience of the world. Although the ear has developed its own system for looking after itself, it’s prone to damage over time, particularly if you like your music loud. Thankfully, modern technology is available today to replicate the complex process of hearing. Modern hearing aids and cochlear implants can help those experiencing hearing difficulty regain the hearing world that has been lost.