शुक्रवार, 29 दिसंबर 2017

What is hearing loss?

You know what hearing is, but what is hearing loss? Hearing loss, or hearing impairment (say: im-pare-ment), happens when there is a problem with one or more parts of the ear or ears, the nerves coming from the ears, or the part of the brain that controls hearing. 

"Impairment" means something is not working correctly or as well as it should.

How Hearing Works



To understand how and why hearing loss happens, it helps to know how the ear works. The ear is made up of three different sections: the outer ear, the middle ear, and the inner ear. These parts work together so you can hear and process sounds. The outer ear, or pinna (the part you can see), picks up sound waves and the waves then travel through the outer ear canal.
When the sound waves hit the eardrum in the middle ear, the eardrum starts to vibrate. When the eardrum vibrates, it moves three tiny bones in your ear. These bones are called the hammer(or malleus), anvil (or incus), and stirrup (or stapes). They help sound move along on its journey into the inner ear.
The vibrations then travel to the cochlea, which is filled with liquid and lined with cells that have thousands of tiny hairs on their surfaces. There are two types of hair cells: the outer and inner cells. The sound vibrations make the tiny hairs move. The outer hair cells take the sound information, amplify it (make it louder), and tune it. The inner hair cells send the sound information to your hearing nerve, which then sends it to your brain, allowing you to hear.

What Causes Hearing Loss?


Hearing loss can happen because a person was born with parts of the ear that didn't form correctly and don't work well. Other problems can happen later because of an injury or illness, including:
  • middle ear fluid
  • serious infections, such as meningitis
  • head injury
  • listening to very loud music, especially through headphones or ear buds
  • repeated exposure to loud sounds, such as machinery
Lots of kids have had ear infections, which also can cause hearing loss. Permanent hearing loss from an ear infection is rare, though. 
Hearing loss that occurs gradually as you age (presbycusis) is common. About 25 percent of people in the United States between the ages of 55 and 64 have some degree of hearing loss. For those older than 65, the number of people with some hearing loss is almost 1 in 2.
Aging and chronic exposure to loud noises are significant factors that contribute to hearing loss. Other factors, such as excessive earwax, can temporarily prevent your ears from conducting sounds as well as they should.
You can't reverse most types of hearing loss. However, you don't have to live in a world of muted, less distinct sounds. You and your doctor or a hearing specialist can take steps to improve what you hear.

More On Hearing Loss

Listen up! Don't take your ears for granted. Hearing loss is the third most common health problem in the U.S, and it can affect the quality of your life and relationships. About 48 million Americans have lost some hearing.

Certain conditions, including age, illness, and genetics, may play a role in hearing loss. Modern life has added a host of ear-damaging elements to the list, including some medications and plenty of sources of loud, ongoing noise.
With so many untreatable cases of hearing loss, prevention is the best way to keep hearing long-term. If you've already lost some hearing, there are ways to stay connected and communicate with friends and family.




What Causes Hearing Loss?


Advanced age is the most common cause of hearing loss. One out of three people age 65-74 has some level of hearing loss. After age 75, that goes up to one out of every two people.
Researchers don't fully understand why hearing declines with age. It could be that lifetime exposure to noise and other damaging factors slowly wear down the ears' delicate mechanics. Your genes are also part of the mix.
Noise wears down hearing if it's loud or continuous. The Centers for Disease Control (CDC) reports that about 22 million American workers are exposed to dangerous noise levels on the job. This includes many carpenters, construction workers, soldiers, miners, factory workers, and farmers.


Degrees of hearing loss

When measured together by your hearing healthcare professional, dB and Hz tell the degree of hearing loss you have in each ear.
  • Mild hearing loss: If one-on-one conversations are fine but you’re having difficulty understanding some words when there’s a lot of background noise, you may have mild hearing loss. Technically speaking, it’s defined as having hearing loss between 26 and 40 dB in the speech frequencies.
  • Moderate hearing loss: At this level, you are asking people to repeat themselves a lot during conversations – in person and on the telephone. Individuals with this degree of hearing loss cannot hear sounds lower than 40-69 dB.
  • Severe hearing loss: If you can’t hear what people are saying without the use of a hearing aidor other amplification, or you tend to rely on reading lips to understand the conversation, you may have severe hearing loss. Individuals with this degree of hearing loss cannot hear sound lower than 70-94 dB.
  • Profound hearing loss: If you have profound hearing loss, you can only hear extremely loud conversation or sound – and even then it’s difficult to understand without a hearing aid or cochlear implant. You may prefer using sign language to communicate. Individuals with this degree of hearing loss cannot hear sound lower than 95 dB.

What is a decibel, and how is it measured?

The decibel (abbreviated dB) is the unit used to measure the intensity of a sound. The decibel scale is a little odd because the human ear is incredibly sensitive. Your ears can hear everything from your fingertip brushing lightly over your skin to a loud jet engine. In terms of power, the sound of the jet engine is about 1,000,000,000,000 times more powerful than the smallest audible sound. That's a big difference!
On the decibel scale, the smallest audible sound (near total silence) is 0 dB. A sound 10 times more powerful is 10 dB. A sound 100 times more powerful than near total silence is 20 dB. A sound 1,000 times more powerful than near total silence is 30 dB. Here are some common sounds and their decibel ratings:
  • Near total silence - 0 dB
  • A whisper - 15 dB
  • Normal conversation - 60 dB
  • A lawnmower - 90 dB
  • A car horn - 110 dB
  • A rock concert or a jet engine - 120 dB
  • A gunshot or firecracker - 140 dB
You know from your own experience that distance affects the intensity of sound -- if you are far away, the power is greatly diminished. All of the ratings above are taken while standing near the sound.
Any sound above 85 dB can cause hearing loss, and the loss is related both to the power of the sound as well as the length of exposure. You know that you are listening to an 85-dB sound if you have to raise your voice to be heard by somebody else. Eight hours of 90-dB sound can cause damage to your ears; any exposure to 140-dB sound causes immediate damage (and causes actual pain). See this page for an exposure "ruler."

References:
(1)https://www.mayoclinic.org/diseases-conditions/hearing-loss/symptoms-causes/syc-20373072
(2)http://kidshealth.org/en/kids/hearing-impairment.html

(3)https://www.webmd.com/a-to-z-guides/hearing-loss-causes-symptoms-treatment#1

(4)http://www.nhcsinc.com/average_hearing_level.htm

(5)https://www.healthyhearing.com/report/41775-Degrees-of-hearing-loss

https://science.howstuffworks.com/question124.htm(6)

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