How Sound Travels • First, sound is collected by the pinna (the visible part of the outer ear) • Then, it is directed into the outer ear canal • Next, sound makes the eardrum vibrate • Now, the vibration causes three tiny bones in the inner ear to vibrate • Hammer • Anvil • Stirrup
How Sound Travels • Finally, the vibration is transferred to the snail-shaped cochlea in the inner ear • The cochlea is lined with sensitive hair cells (cilia) • The hair cells (cilia) trigger the generation of nerve signals that are sent to the brain
Anatomy of the Ear • Outer Ear • Pinna • Ear Canal • Outer layer of the eardum • Middle Ear • Hammer • Anvil • Stirrup • Inner Ear • Cochlea • Nerves • Semicircular Canals
Outer Ear • Pinna- the visible part of the outer ear. It collects sound and directs it into the outer ear canal. • Ear Canal- the tube through which sound travels to the eardrum • Outer layer of eardrum- (tympanic membrane) vibrates when sound waves reach it
Middle Ear • Hammer (Malleus)- a tiny bone that passes vibrations • Anvil (Incus)- a tiny bone that passes vibrations from the hammer to the stirrup • Stirrup (Stapes)- a tiny, U-shaped bone that passes vibrations from the stirrup to the cochlea. This is the smallest bone in the human body. (.25 to .33 cm long) • Eustachian tube- a tube that connects the middle ear to the back of the nose; it equalizes the pressure between the middle ear and the air outside.
Inner Ear • Cochlea- a spiral-shaped, fluid-filled inner ear structure; it is lined with cilia (tiny hairs) that move when vibrated and cause a nerve impulse to form. • Nerves- these carry electro-chemical signals from the inner ear (the cochlea) to the brain. • Semicircular Canals- Fluid filled tubes attached to the cochlea that help us maintain our sense of balance.
Can you label the ear? Semicircular Canals Stirrup Nerves Anvil Hammer Pinna Cochlea Eardrum Eustachian Tube Outer Ear Canal
Hearing Loss • There are three kinds of hearing loss: • Sensorineural • Conductive • Mixed hearing loss
Sensorineural Hearing Loss • Also known as nerve deafness • the inner ear or actual hearing nerve itself is damaged • About 90% of all people with hearing impairments suffer from sensorineural hearing loss • Most common
Conductive Hearing Loss • outer and/or middle part of the ear fail to work properly • Sounds become "blocked" and are not carried all the way to the inner ear (where hearing is still normal) • Not permanent; temporary hearing loss
Mixed Hearing Loss • A combination of a conductive and sensorineural hearing loss • Both the middle and inner ear are involved
Causes of Conductive Hearing Loss • a buildup of fluid in the middle ear • wax in the ear canal • puncturing of the eardrum • problems or injury to the bones or membrane — which carry sound from the external ear through the middle ear to the inner ear.
Sensorineural Hearing Loss • Usually permanent • not medically or surgically treatable • In most cases, the cillia or the nerves from the inner ear to the brain are irreparably damaged. • wearing hearing aids may be of significant benefit
Causes of Sensorineural Hearing Loss • the natural aging process • exposure to loud noises • infection or other disease • a genetic disorder • Tinnitus, or ringing in the ears, is usually associated with sensorineural hearing loss
Causes of a Mixed Hearing Loss • This hearing disorder can also occur when a person first just has a permanent sensorineural hearing loss and then also develops a conductive hearing loss. • For example, a person who already has a sensorineural loss gets a middle ear infection, and the two types of loss combine to create a greater hearing loss. • Some other instances of mixed hearing loss are the result of the outer and inner ear being malformed, which causes both types of hearing loss
Treatment • Conductive hearing loss can be easier to remedy than sensorineural or mixed hearing loss. • It is usually treatable with either medical or surgical intervention • In cases where medical/surgical intervention is not an option, a hearing aid can be very helpful.
Treatment • Sensorineural hearing loss is usually permanent • no medically or surgically treatable. In most cases, the nerves from the inner ear to the brain are irreparably damaged. • However, most people with this hearing loss find wearing hearing aids to be of significant benefit
Treatment for Mixed Hearing Loss • With mixed hearing loss, the conductive part may be treated, but the sensorineural part is usually permanent.
Levels of Hearing Loss • Bilateral- both ears are impaired • Unilateral- one ear is impaired
Bilateral Hearing Loss • Mild • Moderate • Severe • Profound
Mild Hearing Loss • A mild hearing loss may cause you to miss 25-40% of the speech signal. Usually this results in problems with clarity since the brain is receiving some sounds but not all of the information. Symptoms of mild hearing loss include problems understanding someone farther away than a normal distance for conversation, or even up close if the background environment is noisy. Weak voices are also difficult to understand for people with mild hearing losses.
Moderate Hearing Loss • A moderate hearing loss may cause you to miss 50-75% of the speech signal. This means you would not have problems hearing at short distances and understanding people face-to-face, but you would have problems if distance or visual cues changed. Symptoms of moderate hearing loss include problems hearing normal conversations and problems hearing consonants in words
Severe Hearing Loss • People with severe hearing loss have difficulty hearing in all situations. Speech may be heard only if the speaker is talking loudly or at close range. A severe hearing loss may sometimes cause you to miss up to 100% of the speech signal. Symptoms of severe hearing loss include inability to have conversations except under the most ideal circumstances (i.e., face-to-face, in quiet, and accompanied with speechreading).
Profound Hearing Loss • Profound hearing loss is the most extreme hearing loss. A profound hearing loss means that you may not hear loud speech or any speech at all. You are forced to rely on visual cues instead of hearing as your main method of communication. This may include sign-language and/or speechreading (also commonly referred to as "lipreading")
How Hearing Loss is Measured • Decibels (dB)- the intensity (volume or loudness) of a sound • A whisper is about 20 dB • loud music (some concerts) is around 80 to 120 dB • and a jet engine is about 140 to 180 dB • Usually, sounds greater than 85 dB can cause hearing loss in a few hours; louder sounds can cause immediate pain, and hearing loss can develop in a very short time
How Hearing Loss is Measured • Hertz- a range of frequencies • The tone of sound is measured in cycles per second (cps) or Hertz. • Low bass tones range around 50 to 60 Hz • Shrill, high - pitched tones range around 10,000 Hz or higher • The normal range of human hearing is about 16 Hz to 16,000 Hz • Some people can hear within a slightly higher range • Animals can hear up to about 50,000 Hz.
Identifying Hearing Loss • Ranges have been established to help people identify how much difficulty they should expect from their hearing loss. The typical ranges for an adult are: • -10dB to 25dB = Normal range • 26dB to 40 dB = Mild hearing loss • 41 dB to 55 dB = Moderate hearing loss • 56 dB to 70 dB = Moderately Severe hearing loss • 71 dB to 90 dB = Severe hearing loss • over 90 dB = Profound hearing loss
Audiogram • Hearing loss is plotted on an audiogram • Right ear is represented by a red circle • Left ear is represented by a blue X
Audiogram • 10dB to 25dB = Normal hearing • 26dB to 40 dB = Mild hearing loss • 41 dB to 55 dB = Moderate hearing loss • 56 dB to 70 dB = Moderately • Severe hearing loss • 71 dB to 90 dB = Severe hearing loss • over 90 dB = Profound hearing loss
Identify the Hearing Loss What type of hearing loss is it?
What Causes Hearing Loss? You tell me!