If you Google "deaf," "hard of hearing" or "hearing impairment," there are a lot of results. However, it can be overwhelming and confusing.
The terms are related but hold slightly different implications. They are not mutually exclusive. For example, someone who is deaf is also hearing impaired. Someone who is deaf in one ear is also partially deaf and hearing impaired. You get the idea.
What is the difference, if any, between being deaf, hearing impaired and hard of hearing?
Being "deaf" usually means that you cannot hear sound or noise at all. Sometimes people call this "profoundly deaf." Sometimes, when a person can hear muffled noise but cannot make out distinct sounds or words, that is also referred to as deaf. A person can be deaf in one ear or both ears.
Being "partially deaf" means that one can only partly hear - that could be in terms of volume, sound quality (clarity) or both. For example, being partially deaf could mean that sound is muffled or that one cannot distinguish well between different "high pitch" consonant sounds (like a "f" and a "th" sound or a "b" or "v" sound). It could mean that certain sounds cannot be heard but others can be heard. It could mean that a person has some hearing out of one ear but not the other. It can also mean that a person can hear noises (like a drum beat or a siren) but cannot hear distinct specific sounds (like words or music). In other words, it could mean that a person has some ability to detect some noise or sound but lacks the ability to hear clearly. Therefore, everything that can be heard by someone who is normal cannot be heard by someone who is partially deaf.
"Hearing loss" usually means that a person has lost some ability to distinguish between different kinds of sounds and/or has lost the ability to hear clearly unless the volume is high. Usually the cause of hearing loss is damage due to the person listening to loud noises or music or due to aging.
"Hearing impairment" refers to any situation where a person cannot hear clearly regardless of whether the person was born with the absence of hearing or had an experience that resulted in a loss of hearing.
There are two types of hearing loss:
- Sensorineural hearing loss
- Conductive hearing loss
Sensorineural hearing loss is caused when the anatomy of the inner ear and/or auditory nerve is incomplete, damaged or not functioning properly.
Conductive hearing loss means that the middle ear, the anatomy that "conducts" sound waves from the open air to the inner ear, is not functioning properly due to damage, malformation or absence of middle ear anatomy.
Causes of deafness and hearing impairment
There are three main "causes" of hearing impairment or deafness. First, a person can be born with auditory anatomy that is not functioning properly. Second, a person can experience an illness, infection, accident or event that damages auditory anatomy. Third, a person can age and through the aging process, the person's auditory anatomy can break down resulting in decreased auditory function.
About 2-3 out of every 1,000 babies born in the United States are born deaf or hard of hearing. That is about .3% of the population that has congenital deafness. People who are deaf due to microtia fall in this category.
By the time people are adults, up to 15% of the US population experiences hearing loss. The cause of the majority of adult hearing loss is listening to loud noises or music over a prolonged period of time which results in permanent damage to the cilia in the inner ear (see below for more details). Amongst the elderly, an estimated 20% experience hearing impairment.
Therefore, most people who have hearing loss were not born with a hearing impairment.
Everyone knows the story of Helen Keller, who suffered a high fever and lost her hearing as a young child. The exact cause of Beethoven's deafness in his 20s is unknown. Some historians believe it came about from an illness; others attribute his deafness to a falling accident. We all know that you're supposed to wear ear plugs at rock concerts in order to protect the tiny hairs (cilia) in your inner ears that move and generate electrical impulses that are transmitted to your auditory nerve (to be interpreted as sound by your brain). Listening to loud noises or music over a prolonged period of time is one of (if not the number one) cause of hearing loss in the United States.
If there's one thing you take away from this website, it should be:
Wear earplugs at rock concerts!
A common cause of hearing loss is aging. Age-related hearing loss can be caused by prolonged exposure to intense, high decibel noises (same as above) as well as diseases that are more prevalent in the elderly such as hypertension and diabetes. The reason why hypertension (high blood pressure) can result in hearing loss is that the tiny blood vessels in the inner ear become damaged and cannot adequately execute their function of feeding and nourishing the inner ear, including the nerves in the ear. The reason why diabetes is associated with hearing loss is that the high levels of sugar in the blood can damage blood vessels and nerves in the inner ear. Meanwhile, low levels of sugar in the blood can damage the auditory nerve that transmits electrical impulses to the brain.
There is an excellent animated video and description of how hearing works at this website (click on the illustration).
Why does it matter?
The deaf and hard-of-hearing are frequently lumped together into one category. For many reasons, this is good. At the end of the day, the more people who are aware of hearing issues, the more sensitive the overall population will be to issues that the hearing impaired face.
However, lumping everyone who is hard of hearing together can sometimes create problems, too. The reason why it's important to understand the different causes of deafness is that the public policy implications to address different types of deafness are different.
There is not a one-size-fits all solution.
For example, someone who is born profoundly deaf in both ears without a functioning auditory nerve cannot hear spoken word from birth, even with a bone anchored hearing aid. For this individual, learning to communicate in any way - perhaps by sign language or reading lips - is critical so that the baby can learn to express himself or herself at an early age. For someone whose auditory nerve is functioning but who is deaf due to the absence of an ear canal, a bone anchored hearing aid can help the baby hear and make out spoken words and therefore learn to speak. Therefore, ensuring proper hearing through a bone anchored hearing aid may be the top priority for a baby with this type of deafness.
Furthermore, children with different types of hearing-related conditions need to learn how to discuss their conditions with peers and teachers and advocate for themselves in ways that make sense. The "talking points" are different, depending on the type of deafness that the child has. A child who is deaf or hard of hearing but has no outward physical sign of having a medical condition may need to be more proactive about communicating his or her learning needs. Meanwhile, a child with a condition like microtia, which is almost always accompanied by a physical element, may need to learn how to discuss his or her condition in a different way.
Audiograms
If you find yourself saying, "what?" a lot, you should get your hearing tested.
When you get your hearing tested, the results are displayed on a graph called an audiogram. An audiogram has how loud or soft a sound is on the vertical axis and the frequency (or pitch) on the horizontal axis. What is charted is the softest sound (in terms of volume) that you can hear of different frequency sounds. The softest sounds are represented at the top of the graph, and the loudest sounds are represented at the bottom of the graph.
For a person with normal hearing, you would expect to see two (more or less) horizontal lines somewhere close to the top of the graph. This would show that at various frequencies (along the x-axis), both ears can hear fairly soft sounds. If one line is lower than the other, that means that one ear has more hearing loss than the other. If the line is not more or less horizontal, it means that there are certain frequencies that are harder for you to hear.
Lower frequency (pitch) sounds tend to be lower and louder. They include: z, v, j, m, d, b, n, ng, ee, l, a, i, o and r. Higher frequency (pitch) sounds tend to be higher and softer. They include: f, th, s and k. Sounds like u, ch, sh, p, h and g are in the middle.
Someone with normal hearing can hear all frequencies at 0 to 10 decibels. Mild hearing loss is when the softest one can hear is between 10-50 decibels. Moderate hearing loss is when the softest one can hear is at 45 to 70 decibels. Severe hearing loss is when the softest one can hear is above 70 decibels.
Sources: Department of Defense, Hearing Centers of Excellence; WebMD, Understanding Hearing Loss; The Mayo Clinic, Hearing Loss; World Health Organization: Deafness and Hearing Loss; Johns Hopkins Medicine, Hearing Loss; American Diabetes Association; The Hearing Review: "ABI Trial Helps Children Born without Hearing Nerve," Disabilities Opportunities Internetworking and Technology (DO-IT)