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How Hearing Works: A Human’s Most Important Sense

There is no other sense quite as powerful as our ability to hear. Being able to effectively communicate with our friends and loved ones allows us to form lasting connections and relationships. When our sense of hearing is lacking, it creates a gap in our life that makes us feel disconnected from those we care for. This is how hearing works, and what can be done when it doesn’t.

ear-anatomyThe Ear’s Structure

Outer Ear

The outer ear is also known as the pinna and it includes everything that you can see on the ear’s surface as well as the ear canal. The outer ear is designed to help in focusing sound, some mammals even have the ability to move their ears to localize sound more effectively. While the pinna takes in the sound, the ear canal transports those sound waves to the middle ear.

Middle Ear

The eardrum is located at the end of the ear canal, this is where the middle ear begins. Within the middle ear are the three smallest bones in the human body, malleus, incus and stapes, also known as the ossicles. These three bones are located inside an air-filled chamber and are protected by the stapedius and the tensor tympani muscles. The ossicles connect the eardrum to the inner ear. When sound waves penetrate the eardrum it moves, which then causes the ossicles to move. This results in a sound wave being altered to a mechanical vibration.

Inner Ear

The cochlea, a snail shaped bony structure, is located within the inner ear and and contains the sensory organs necessary for balance and hearing. The cochlea contains two fluids, endolymph and perilymph, as well as the Organ of Corti, which divides the cochlea lengthwise. Within the Organ of Corti are hair cells. When the inner ear receives mechanical vibrations from the ossicles, the cochlea’s fluid then stimulates those hair cells. Each hair cell responds only to specific pitches, so depending on what you hear, only certain hair cells respond.

Auditory Nerve

Whichever hair cells were stimulated within the Organ of Corti are then altered to nerve impulses. The auditory nerve then sends these nerve impulses to the cochlear nucleus, or mid-brain. These impulses are then sent to the auditory cortex which is where sound if first consciously experienced. Wernicke’s Area is the part of our brain that is responsible for interpreting sounds into speech.

How Hearing Works

Now that we know each function of the middle ear, we have a better understanding ofhow hearing works.

  1. The outer ear, or pinna, retrieves sound waves and then the ear canal carries that sound to the eardrum.
  2. The eardrum receives those sound waves and vibrates in response.
  3. Sound vibrations from the eardrum cause the ossicles (malleus, incus, and stapes) to vibrate in response, to the cochlea.
  4. The sound vibrations cause inner ear fluid to stimulate tiny hairs within the cochlea to move.
  5. The movement of the hair cells produce neural impulses that are received by the auditory nerve.
  6. The brain receives these neural impulses and they are interpreted into sounds.

When Hearing Doesn’t Work

There are several reasons why your hearing may not be working to its full capacity. By understanding these various types of hearing losses, you will be able to better identify which hearing loss you may have as well as how it can be treated.

Conductive Hearing Loss

According to the American Speech-Language-Hearing Association (ASHA), a conductive hearing loss may be caused from the following:

  • Fluid in the middle ear from colds
  • Ear infection (otitis media)
  • Allergies (serous otitis media)
  • Poor eustachian tube function
  • Perforated eardrum
  • Benign tumors
  • Impacted earwax (cerumen)
  • Infection in the ear canal (external otitis)
  • Swimmer’s Ear (otitis externa)
  • Presence of a foreign body
  • Absence or malformation of the outer ear, ear canal, or middle ear

A conductive hearing loss is typically an outer ear problem where sound is not effectively transported through the ear canal. This results in a poor vibration of the eardrum and ossicles. The result of a conductive hearing loss includes only hearing faint sound, or hearing a reduced sound level. Typically this type of hearing loss can be fixed surgically or medically.

Sensorineural Hearing Loss

If the inner ear, or cochlea gets damaged it often results in a sensorineural hearing loss (SNHL). SNHL is the most common type of hearing loss, ASHA lists the following as possible causes of SNHL:

  • Illnesses
  • Drugs that are toxic to hearing
  • Hearing loss that runs in the family (genetic or hereditary)
  • Aging
  • Head trauma
  • Malformation of the inner ear
  • Exposure to loud noise

If you suffer from a SNHL, your ability to comprehend faint noises is reduced and speech can sound muffled and unclear. Unfortunately, usually this type of hearing loss can’t be surgically or medically treated.

Mixed Hearing Loss

A mixed hearing loss occurs when there is a combination of a conductive hearing loss and a sensorineural hearing loss. This means, that there is some type of damage in the outer ear as well the inner ear. If your hearing loss is predominately a conductive hearing loss, this will result in speech sounding mostly understandable if there is limited background noise. If your mixed hearing loss is predominately a SNHL, speech will be difficult to understand even if it seems loud enough.

Varying Degrees of Hearing Loss

Regardless of which type of hearing loss you have, there are varying degrees of how poor your hearing is. Audiologists classify hearing into mild, moderate, severe and profound. Getting your hearing tested is the only way to know the severity of your hearing loss.

How To Manage Hearing Loss

No one should have to live with the frustration and loneliness that comes from having a hearing loss. After getting your hearing tested, your audiologist will recommend one of the following to improve your hearing, and your way of life.

  • Hearing Aids
    • Hearing aids are the most common therapeutic device to help those who suffer from a hearing loss. Once you’ve established your degree of hearing loss, with the help of a hearing specialist, you will choose a hearing aid that fits all of your needs. Your hearing specialist or audiologist will go over every aspect of your hearing aid so that you can leave feeling confident in how to wear them and how to care for them.
  • Cochlear Implants
    • A cochlear implant is a surgically implanted medical device that directly stimulates the auditory nerve by bypassing the damaged structure within the inner ear. This therapeutic measure is only for those with a severe to profound hearing loss and only if their hearing is not improved with hearing aids.
  • Hearing Assistive Technology
    • While hearing aids and cochlear implants will greatly benefit your hearing, they won’t perfect it completely. Assistive listening devices (ALDs) are designed to improve the functionality of your hearing aid or cochlear implant. Thanks to the Americans with Disabilities Act, most public places are required to provide an ALD so you can hear speakers even when they’re far away from you.

Hearing is one of our most amazing senses, and if you find that you’re not experiencing it to it’s full capacity there are plenty of ways you can correct this problem.

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