How We Hear & Hearing Loss

THE THREE DIVISIONS OF THE EAR

The ear is actually a system of three interrelated parts that function together for the perception of sound and the maintenance of balance.

The Outer Ear

The outer ear is what most people consider “the ear”. It consists of the flexible, fleshy part (the pinna) as well as the ear canal. The eardrum separates the outer ear from the middle ear space.

The Middle Ear

The middle ear is a space in the skull, which lies behind the eardrum and is in close proximity to many important structures. The bottom of the space is closely related to the carotid artery and jugular vein. At the front of the space is the opening of the eustachian tube (the conduit which connects the middle ear space to the back of the nose).

The innermost wall has two openings to the inner ear, one for the stapes (the oval window) and one called the round window, both function in the transduction of mechanical sound to nerve impulses in the inner ear. In addition, a very important nerve, which controls the movement of the face and is involved in taste, runs along this bony wall in its own canal as it travels to exit the skull.

The back most wall of the middle ear has an opening to a system of air cells located within the bone behind the ear (mastoid bone), called the mastoid air cells. Finally, three small bones span this space and conduct sound energy from the ear drum to the inner ear. These bones are called the malleus, the incus, and the stapes (a.k.a. the hammer, the anvil, and the stirrup). As you can see, the middle ear is a busy and very important area. This is also a common site of disease and hearing loss.

The Inner Ear

The inner ear is actually a series of fluid filled spaces housed within the bone of the skull. These spaces include the cochlea, which is involved in hearing, and the semicircular canals, which are involved in balance. Within these spaces, bathed in fluid, are delicate neurosensory tissues and fine nerve endings, which will ultimately conduct both balance and hearing information to the brain.

How the Ear System Works

  1. Sound energy in the environment is collected and funneled to the eardrum by the fleshy part of the ear (the pinna) and the ear canal.
  2. The sound waves strike the eardrum causing it to vibrate.
  3. The vibrations are transmitted to the inner ear from the eardrum through the three bones spanning the middle ear space (the malleus, incus, and stapes).
  4. The base of the stapes sits in one of the openings to the inner ear (the oval window). The vibrations of the stapes produce waves in the fluid that fills the cochlea.
  5. The fluid pushes against the sensory membranes in the cochlea.
  6. This movement causes tiny sensory cells located here (hair cells) to transmit electrical impulses to delicate nerve fibers of hearing, which are attached to them.
  7. This impulse is then sent to the brain where it is interpreted as sound.

The balance system of the inner ear is very similar to that described above expect this system is activated by head motion (instead of sound vibrations transmitted through the ossicular chain).

Facts of Hearing Loss

  • Twenty-five million people in the U.S. suffer from hearing loss of some type.
    • 15-20% may benefit from a procedure to improve their hearing.
    • Most will benefit from hearing amplification, regardless of the type of hearing loss.
  • Approximately 30% of people over the age of 65 and 70-80% over 75 years of age have a significant hearing impairment.
  • Baby boomers are showing increased hearing loss at earlier ages.
  • Hearing is an integral part of communication
  • Studies have shown that hearing loss in the elderly reduces involvement in social activities and leads to feelings of isolation and depression.
  • In children, hearing is essential for appropriate speech and language development.

Causes of Hearing Loss

There are many factors that can lead to hearing loss, and sometimes multiple factors contribute at once. Some common causes are listed below.

The Outer Ear

  • Ear canal blockage with wax (cerumen) or a foreign body
  • Narrowing of the ear canal
  • Infection of the ear canal (otitis externa); often this is accompanied by pain, drainage, itching and swelling

The Middle Ear

  • Improper formation of the ear bones from birth
  • A hole in the eardrum (tympanic membrane perforation)
  • Infection in the middle ear space (otitis media)
  • Dysfunction of the eustachian tube and fluid build up (serous otitis media)
  • Skin cyst formation in the middle ear (cholesteatoma); this can perforate the eardrum, cause infection, and erode the ear bones or bone of the skull
  • Head injury with dislocation of the middle ear bones
  • Otosclerosis. This is an abnormal growth of bone around the base of the stapes bone, which prevents its proper motion

The Inner Ear

  • Gradual decline in hearing with aging (presbycusis)
  • Sudden or prolonged very loud noise exposure
  • Gradual exposure over years to loud noise
  • Congenital or hereditary hearing loss
  • Certain viral infections
  • Certain skull fractures
  • Certain medications (diuretics, antibiotics, chemotherapeutic agents)
  • Rarely, tumors of the hearing or balance nerve

What is Tinnitus?

Tinnitus is very common and can be annoying and distracting. Almost 37 million Americans have tinnitus in their ear or ears. It may come and go or might be a constant bother. It might be soft or loud, low pitched (roaring), or high-pitched (ringing) kind of sound. More than 7 million people are so badly affected that they can’t lead normal lives.

What Might Cause Tinnitus?

There are various causes including a plug of wax, allergy, ear infection, circulatory problems, certain medications, and prolonged exposure to loud noise.

Learn More

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Florida Gulf Coast Hearing Center - The Best in Naples Hearing Healthcare
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Naples

2180 Immokalee Rd. #101
Naples, FL 34110

(239) 514-2419

Estero

9250 Corkscrew Rd. #3
Estero, FL 33928

(239) 734-3724

Pine Ridge

6101 Pine Ridge Rd.
Naples, FL 34119

(239) 734-3732

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