The Amazing Human Ear and How We Hear
As audiologists, we think that hearing is an absolute marvel of science. We’re not even biased! The ear of a human fetus in the womb can detect and respond to sounds starting at just 30 weeks old. After birth, we continue to recognize our own mother’s voice, along with other familiar sounds. As we grow up, hearing is the first of our senses we use each morning, as the alarm wakes us for work or school. Every day, hearing permeates everything we do. This ranges from the basics of speaking and understanding what others are saying to us, to being alerted by vital warning sounds, like a fire alarm. The sense of hearing is responsible for saving lives! Hearing can also produce some really amazing psychological phenomena, like when a song you haven’t heard in years invokes long-forgotten memories. Even when we sleep, we still hear the world around us. We just don’t process these sounds as the brain overrides them for us.
We could spend all day talking about the fascinatingly complex relationships between the ear’s anatomy, the auditory system and how the brain processes sound. But, we’ll settle for sharing a quick guide to how the ear works. When you become familiar with the anatomy and workings of your ear, you can better notice and prevent hearing loss before it’s too late. Knowledge is power!
Why does my ear look the way it does?
The outer ear is a curious looking part of our human anatomy, but those curves and crevices – made of cartilage – have an important job. Ears are specifically shaped to modify high-frequency sounds and funnel them about 2.5cm down the ear canal to the eardrum and middle ear.
What’s inside my ear?
The middle ear begins at the eardrum. When sound waves hit the eardrum, they transform from sound energy to mechanical energy. Within the middle ear are three tiny bones called the ossicles. These bones in the ear and in fact the smallest in the human body. Their anatomical names are the malleus, incus, and stapes, but you may know of them as the hammer, anvil, and stirrup, due to their distinctive shapes. The stapes, or stirrup, is just 2.5mm on its longest side, and all three of these bones could fit easily on your fingertip. When the eardrum vibrates, the ossicles vibrate too, bridging the gap to the cochlea and inner ear.
The cochlea, meaning ‘snail’ in Latin, is a bony structure of the inner ear named for its spiralled shape. It’s filled with fluid and contains around 24,000 tiny hair fibres that are vital to our hearing ability. When vibrations arrive from the middle ear, they enter the cochlea through a membrane called the oval window. The vibrations then stimulate the network of hairs, which send messages to the auditory nerve via electrical signal. Different pitches of sound stimulate different hairs, which helps the brain to recognise the sound is coming in.
When sound arrives at the brain, it will take pathways to the auditory cortex. In a person with a healthy hearing system, sound is processed and attached with meaning, so we can understand it. This happens almost instantaneously.
Not just a one-trick pony
Did you know the inner ear has two key jobs to do? It is also responsible for our sense of balance! We know the vestibular as the organ of balance. It consists of three semicircular canals, filled with fluid and tiny hairs. The tiny hairs send messages to the brain continuously as the fluid moves, to help the brain register the body’s movements, along with input from the eyes, muscles and joints.
What happens when something goes wrong?
As you can imagine, in such an intricate system, sometimes things can go wrong. This can result in what we know as a hearing loss. The type of hearing loss an individual suffers depends on which part of the hearing system was damaged. And how. For example, loud noises can damage the cells in the inner ear called outer hair cells. These are the tiny hairs within the cochlea that look after the amplification of sound. Once these hairs are damaged they can’t regenerate. It’s important to always protect your hearing from excessively noisy environments. Note that these outer hair cells also deteriorate with age. By the age of 70, we’ll only have around 70% of ours left if we have looked after our hearing well. In both cases – noise damage and age – hearing aids can be a really effective treatment.
If you experience a condition of the outer or middle ear, it’s likely to cause conductive hearing loss. That means that the cochlea isn’t receiving sound as efficiently as it would in a healthy ear. Examples of this might be an ear infection or perforated eardrum. Read up on how to care for your ears and hearing in our blog, and learn more about some common ear infection symptoms.
So there you have it. The ear and auditory system is one of the most amazing, but delicate, parts of human anatomy in our humble opinion! And that’s why our audiology team are passionate about keeping it in tip-top shape. If you’re suffering from hearing loss, or simply want to experience the joys of hearing at their best, book an appointment with an ihear hearing specialist for your free hearing check.
