Definition Of Hearing
Hearing Definition: the faculty of perceiving sounds.
What Is Hearing?
Hearing is the process of perceiving sound. The process can be broken down into several steps:
- Sound is captured by our outer ear and is directed down the ear canal towards our ear drum.
- The ear drum vibrates when the sound hits it.
- When the ear drum vibrates it also stimulates the bones in the middle ear called the ossicles.
- The middle ear bones amplify and transfer the vibrations to the inner ear by displacing fluid inside the cochlea.
- The displacement of fluid at the oval window sends waves down the cochlea. There are receptors called hair cells that sway back and forth with the waves.
- The swaying of these hair cells generates electrical signals which are sent along the auditory nerve to the brain.
- These electrical signals travel up the auditory brain where it is organised and processed.
- Our perception of sound is dependent on how it is organised and processed by our brain.
For us to effectively hear, each step of the pathway needs to be working efficiently. Let us work through some examples of what happens if things go wrong at each step:
Hearing With The Outer Ear
Our outer ear consists of the pinna (the part that sticks out of our heads) and the auditory canal. Have you ever noticed that our pinna is an odd shape? Almost like a bowl. This is because it has evolved to catch sounds, particularly in the region of human speech. Sometimes things go wrong with our outer ear and this can affect our hearing.
Some people are born without their pinna (atresia), or perhaps have had it surgically altered or removed. This affects their ability to channel sound into the ear canal. This can affect their hearing and ability to tell where sounds are coming from.
Try this: Cup both hands behind your ears. Notice how much louder the world seems. It helps to direct more sounds down the ear canal and can increase the loudness by as much as 10dB.
Cauliflower ear is a common injury in contact sports such as rugby and boxing. The bruising and swelling that occurs on the ear if left untreated can lead to permanent disfigurement of the ear structures. This disfigurement affects the ability of the outer ear to direct sound down the ear canal. Cauliflower ear can also cause narrowing of the ear canal. This can result in an increased risk of wax build up and infections.
Earwax is a mixture of keratin, fatty acids, squalene, alcohol, and cholesterol. It is our bodies way of keeping the ear canals clean. Without a migratory process dead skin that is present in the ear would quickly build up and block the ear canal. This would result in chronic infections, problems with hearing, and significant discomfort. As such, the body has evolved to push out the dead skin along with a few other tricks to reduce the risk of infection and to keep insects from burrowing inside.
Sometimes the migratory process is interrupted and can result in an earwax build up. Using cotton buds, ear plugs, and in-ear headphones are among common reasons for this to occur. All of these can push earwax back into the ear forming a blockade. More wax then builds up behind this blockage and it eventually forms a plug known as impacted wax. This can cause a temporary reduction in your hearing and can also be quite uncomfortable.
Earwax can be safely removed using several approved procedures. The most common practices amongst professionals are microsuction and irrigation. These procedures can safely remove the wax and you should notice an immediate improvement in your hearing again.
Outer Ear Infection
An outer ear infection, otitis externa, is a painful infection of the ear canal and surrounding structures. It often results in a discharge from the ear with accompanied swelling and pain. The discharge may be yellow/green in colour and may have a smell. An outer ear infection can temporarily affect our hearing. Many outer ear infections will clear on their own in 3-5 days but sometimes they do require intervention in the form of antibiotics. It may take a few weeks after the infection has clear for the ear to return to normal.
Hearing With The Middle Ear
The middle ear consists of the ear drum, middle ear space and the ossicles and it plays an important role in our hearing. The middle ear converts soundwaves into a mechanical movement that pushes on the fluid within the inner ear. It also amplifies the sound which increases the sensitivity of our hearing.
The Ear Drum
You have probably heard of the ear drum from your school science lessons and it plays an important role in our hearing. As soundwaves strike the ear drum it vibrates, and these vibrations are transferred through the middle ear by the bones attached to the ear drum called the ossicles.
The primary function of the Ossicles is to transfer the sound from the ear drum to the inner ear whilst simultaneously amplifying the signal to increase the sensitivity of our hearing. The large surface area of the malleus on the ear drum compared to the tiny surface of the stapes on the oval window means that the pressure level is increased by a factor of 10. The high pressure at the stapes is required to displace fluid which is contained within the inner ear.
As well as transferring sound, the ossicles play an important part in protecting our hearing. If a loud sound is detected there is a reflex in the ear that contracts a muscle to restrict the vibrations of the ossicles. This helps to attenuate the signal and protect the inner ear from damage.
The ossicles rarely fail but chronic infections can erode the tiny bones which affects our hearing. They can also be dislocated which means the continuity of the ossicle chain is affected once again lowering our hearing ability. Other conditions such as otosclerosis can also result in malformation of the ossicles which restricts their movement and function resulting in hearing loss. This can sometimes be reversed through surgery.
Perforated Ear Drum
Our ear drum has evolved to be very sensitive to sound but as it is only a thin membrane it is vulnerable to damage. Trauma and infections can result in a hole forming in the ear drum often referred to as a perforation. The perforation prevents the sound from being efficiently converted into mechanical energy and leads to a loss in hearing ability. The ear drum is usually able to self-heal within 4-6 weeks. However, on occasion the hole does not recover, and the individual would either need to tolerate the perforation or have surgery to repair the hole.
Otosclerosis is the occurrence of abnormal bone growth on the ossicles. The excess bone often creates inefficiencies in the transfer of sound from the ear drum to the middle ear resulting in a conductive hearing loss. The condition can sometimes be improved with surgery.
Hearing With The Inner Ear
The inner ear consists of the semi-circular canals, the Cochlea, and the Vestibule. The inner ear has two main functions: balance and hearing.
The semi-circular canals and the vestibule form the part of the ear that helps us to control our balance. This leaves the cochlea, which is responsible for our hearing.
The Cochlea is a highly complex bony structure that contains the Organ of Corti, which is responsible for converting kinetic energy into electrical energy which passes along the auditory nerve to the hearing brain.
As the stapes pushes on the oval window of the cochlea, fluid is displaced, and this stimulates various membranes. The movement of these membranes results in the movement of the hair cells within the Organ of Corti. As these hair cells move back and forth, they activate and deactivate neural pathways which codes information along the auditory nerve
Sensori-neural hearing loss
Sensori-neural hearing loss occurs when there is damage to the cochlea or auditory nerve. With current medicine, it is not possible to reverse damage within the inner ear and as such, any hearing loss is considered permanent. However, researchers are working hard on stem cells to regenerate damaged hearing.
Treating Hearing Loss
Hearing loss is often treated using hearing aids. Hearing aids are designed to amplify external sounds to help improve the sensitivity of our hearing. Hearing aids are improving all the time and they include technology that allows us to fit them remotely.
Test your hearing ability today by taking our online hearing test.
Teleaudiology, a division of telemedicine / telehealth, is the use of video conferencing, telephones, emails, or instant messaging to deliver a remote hearing care service.
Traditionally, you would go to a hospital or a clinic and meet with an audiologist in person. However, with the latest innovations in hearing care we can offer you this service entirely through your computer or smartphone from the comfort of your home, work or on the go.
At Adjust Hearing, we use a combination of synchronous and asynchronous teleaudiology solutions to ensure that our approach is entirely digital. This means you have access to our audiologists 24 hours a day, 7 days a week, 365 days a year.
Can I Buy Hearing Aids Online?
Yes, you can buy your hearing aids online safely from us. It is a simple 3 step process. We provide the gold standard of teleaudiology care and you will be fully informed every step of the way.
How do I book my teleaudiology appointment?
Your teleaudiology appointment can be made through our online booking system. Your initial assessment is free of charge. So, book in today, and tune in to life.