How We Hear
How We Hear
To understand hearing loss, we must first understand how hearing works. The ear is made up of 3 main parts:
- Outer Ear
- Middle Ear
- Inner Ear
The outer ear consists of the visible part of the ear (pinna), the ear canal and the ear drum. Sound waves are collected by the outer ear and are channelled toward the eardrum. The eardrum begins to vibrate.
The middle ear is an air-filled space that contains the three smallest bones in the human body: the malleus, the incus and the stapes. These bones are attached to the eardrum on one side and the inner ear on the other side. The middle ear is also connected to the throat via the Eustachian tube, which makes sure the air pressure is the same on both sides of your eardrum and allows your ears to “pop” when you’re flying in a plane or driving through mountains. The vibration of the eardrum causes movement of the three tiny bones in the middle ear. The movement of these bones transmits the eardrum vibrations to the inner ear
The inner ear consists of the cochlea and the vestibular (balance) system. The cochlea is a snail-shaped bone filled with fluid and thousands of tiny “hair cells” that process sound vibrations. Vibrations enter the cochlea and the fluid is set into motion, like a wave, and the hair cells move in response. When the hair cells move, they send electrical signals along the hearing nerve and toward the brain. The brain then processes these signals to help us understand what we have heard.
Hearing Loss Prevalence
Hearing loss is a significant health issue that affects individuals of all ages. 1 in 10 Canadians are living with some degree of hearing loss and between 20 and 40% of adults over the age of 65 reporting a significant hearing loss. In Canada, hearing loss is the 3rd most common chronic condition behind arthritis and high blood pressure (Statistics Canada, 2002).
Worldwide data show that hearing loss prevalence increases dramatically with age, affecting between 25% and 40% of adults over 65, 40% to 66% of adults over 75, and 80% of adults over 85 years (Pascolini and Smith, 2008). However, hearing loss does not just affect older people; in the United States, 65% of people with a hearing loss are younger than 65 (Kochkin, 2005).
Signs of Hearing Loss
Hearing loss often develops gradually, sometimes over many years. Because of this, people with hearing loss don’t often notice a problem, even though friends and family may be aware of it. Listed below are some common signs of hearing loss that you or a loved one may have noticed.
You might have a hearing loss if you…
- frequently ask people to repeat themselves
- say “pardon me?” or “what?” a lot
- have difficulty hearing in noisy places such as restaurants or parties
- think that other people are mumbling
- have been told that the tv or radio is too loud
- have more trouble hearing women and children’s voices
- have ringing in your ears
- favour one ear over the other
- family or friends have commented that you have hearing difficulty
If any of these sound familiar to you, you may want to consider having your hearing tested by an audiologist, a university-trained professional who specializes in hearing and hearing loss difficulties.
To help you understand the negative impact that a hearing loss may be having in your life, click the link below to complete an online Quick Hearing Check (from the Better Hearing Institute, www.betterhearing.org).
The Quick Hearing Check is not a substitute for a professional hearing test performed by an audiologist. It is designed to help you decide whether you should have your hearing tested by an audiologist.
Types & Causes of Hearing Loss
It is important to note that not all hearing loss is the same. There are different types of hearing loss, depending on which part of the hearing pathway is affected. Hearing loss is categorized into four main types: conductive, sensorineural, mixed, and central hearing loss.
Conductive Hearing Loss
In conductive hearing loss, sound waves at normal levels are not able to reach the inner ear. Conductive hearing loss is caused by problems with the outer or middle ear.
Common causes of conductive hearing loss:
- Excessive earwax
- Narrowing of the ear canal due to inflammation or bony growths
- Torn or damaged ear drum
- Fluid or blood behind the ear drum
- Abnormalities of the middle ear bones
- Outer ear deformities
If a hearing loss is purely conductive, it is often possible to improve hearing with medical or surgical treatment. In some cases conductive hearing losses are permanent, but in these cases, individuals can often benefit from hearing aids.
Sensorineural Hearing Loss
Sensorineural hearing loss is the most common, accounting for 90% of all hearing loss. In sensorineural hearing loss, sound waves reach the inner ear, but the inner ear hair cells or hearing nerve are not working properly.
Common causes of sensorineural hearing loss:
- Aging (presbycusis)
- Noise exposure
- Certain drugs
- Inner ear infections
- Developmental abnormalities
Unlike conductive hearing loss, sensorineural hearing loss is usually permanent and cannot be treated medically or surgically. Once hair cells have been damaged, there is no way to replace or repair them. However, many people with sensorineural hearing loss can benefit from hearing aids.
Mixed Hearing Loss
Mixed hearing loss is a combination of conductive and sensorineural hearing loss. In mixed hearing loss, sound waves are less efficiently transferred to the inner ear, and if they do reach the inner ear, the inner ear hair cells or hearing nerve are not working properly.
Common causes of mixed hearing loss:
- Any of the causes of sensorineural and conductive hearing losses mentioned above
Central Hearing Loss
In central hearing loss, sound waves reach the auditory nerve, but the auditory nerve may have problems sending electrical signals, or the brain may not interpret the signals properly. People with central hearing loss are often able to detect sound but may not be able to interpret or understand it.
Common causes of central hearing loss are:
- Head injury
Central hearing loss can be diagnosed using specialized tests that assess a person’s ability to interpret complex auditory information.
Degrees of Hearing Loss
Between the two extremes of hearing well and hearing nothing, there are many degrees of hearing loss. The degree of hearing loss varies from person to person. The terms used to describe the degree of hearing loss are mild, moderate, moderately severe, severe and profound. Most hearing losses are mild to moderate.
- Mild hearing loss: unable to hear soft sounds, difficulty understanding speech clearly in noisy environments.
- Moderate hearing loss: unable to hear soft and moderately loud sounds, considerable difficulty understanding speech, particularly with background noise.
- Severe hearing loss: some loud sounds are audible but communication without a hearing instrument is impossible.
- Profound hearing loss: some extremely loud sounds are audible but communication without a hearing instrument is impossible.
A hearing test performed by an audiologist can accurately determine your type and degree of hearing loss. Because of the high prevalence of hearing loss in older adults, adults over the age of 50 should include a hearing test as part of their yearly checkup.
Consequences of Hearing Loss
Most people simply associate hearing loss with having a harder time hearing certain sounds. However, the potential impact of hearing loss on a person’s life is far worse than that. Research has shown again and again that untreated hearing loss can have a serious negative impact on psychological, social and emotional well-being.
Untreated hearing loss has been linked to:
- Loneliness and Social Isolation
- Anxiety and Paranoia
- Increased risk of dementia
- Irritability, Stress and Anger
- Reduced Job Performance and Earning Potential
Just as importantly, studies have also shown that these negative consequences are reduced in people who wear hearing aids.
Hearing aid users have:
- Improved social lives
- Better relationships with family members
- Greater independence
- Improved physical health
- Reduced anxiety, emotional instability and depression
- Fewer incidences of confusion
- Increased earning potential
Articles outlining the negative consequences of hearing loss and the benefits of hearing aids are available for download in the Hearing Loss Resources section of this website.
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