How It Works and Things That Can Go Wrong The Ear How It Works and Things That Can Go Wrong

Function of the Ear The ear serves two functions: hearing and balance. The organs for these functions are the cochlea for hearing and the semicircular canals for balance.

How Does the Ear Work? The pinna funnels sound into the ear canal. Sound waves go through the ear canal and vibrate the eardrum (typanic membrane). The vibrations are transmitted through and amplified by the ossicles (middle ear bones). Movement of the ossicles pushes at and pulls away from the fluid in the inner ear.

How Does the Ear Work? (2) The movement of the fluid in the inner ear moves the hairs in the sensory cells of the cochlea. These cells send impulses from the cochlea through the auditory nerve to the auditory cortex of the brain. *The ear is changing sound energy to vibrations, to nerve impulses. Anything that stops the flow of energy can cause hearing loss.

Vocabulary Auditory Cortex – the area of the brain that receives and translates information about sound. Auditory Nerve – a nerve that stretches from the cochlea to the brain. It carries messages from the ear to the brain. Cochlea – a part of the inner ear. It is shaped like a snail. There are many tiny nerve endings inside the cochlea.

Vocabulary (2) Decibel – a unit for measuring how loud or soft a sound is. Ear Canal – the passage that carries sound from the pinna to the eardrum. Eardrum (Tympanic Membrane) – a small opening inside the ear that is covered with skin. The eardrum moves back and forth when sound hits it. The eardrum lies between the outer and middle ear.

Vocabulary (3) Eustachian Tube – tube connecting middle ear to the throat (drains fluid from the ear). Frequency – the number of sound waves per second that a sound makes. This tells how high or low a sound is. Hertz – a unit for measuring the frequency of a sound

Vocabulary (4) Ossicles – malleus, incus, and stapes, the three tiny bones in the middle ear. These are the smallest bones in the body. Outer ear – first section of the ear. It includes the pinna and the ear canal. Middle ear – second section (we can’t see it). It contains the ossicles. Inner ear – third section (can’t see). It contains the semicircular canals, cochlea, and auditory nerve.

Vocabulary (5) Pinna – the part of the ear that we see outside the head. It catches sound. Semicircular Canals – the structures (fluid- filled) that control the sense of balance. Sound Waves – how sound travels. Sound moves in waves that we cannot see.

Types of Hearing Loss Conductive Hearing Loss – anything that goes wrong in the outer or middle ear. These can include: - wax buildup in the ear canal - infections in the ear canal that cause swelling - infection, scarring, or holes in the eardrum - fluid buildup in middle ear - limited movement of the ossicles

Types of Hearing Loss (2) Sensorineural Hearing Loss – any problems which occur in the inner ear. These can include: - drug-induced damage of the cochlea (chemotherapy, etc.) - trauma to the cochlea (blow to the head, noise damage, etc.) - age-related hearing loss (presbycusis)

Types of Hearing Loss (3) - a tumor on the auditory nerve - some infections, such as meningitis Mixed Hearing Loss – both conductive and sensorineural hearing loss. Central Hearing Loss – when there is a problem in the auditory cortex of the brain. This is the least common.

Types of Hearing Loss (4) Many times, Conductive Hearing Loss can be corrected by medication or surgery. Most of the time, Sensorineural or Central Hearing Loss can’t be corrected.

Degrees of Hearing Loss Mild – difficulty hearing soft speech Moderate – difficulty understanding conversa- tions, especially if there is background noise. TV and radio volume must increase. Severe – normal speech is inaudible. May only be able to hear loud or amplified speech. Profound – completely deaf

More than 28 million Americans have some degree of hearing loss More than 28 million Americans have some degree of hearing loss. About 2 million of them are considered profoundly deaf.

Preventing Noise-Induced Hearing Loss Limit your time in loud places. Wear earplugs in noisy situations. Don’t sit too close to speakers at concerts. Turn your headphones down! If the person sitting next to you can hear the music, it’s too loud.

Preventing Noise-Induced Hearing Loss Decibel Levels: 50-60 decibels normal conversation 80-85 city traffic, garbage disposal 90-95 lawn mower 100-120 chainsaw, tractor 130 + headphones 110-140 rock concert, jet take- off, shotgun, jackhammer

Preventing Noise-Induced Hearing Loss At 85 decibels, you should use hearing protection for extended exposure. At 100 or more decibels, you should not go more than 15 minutes without hearing protection. At 140 decibels, repeated exposure of more than one minute can cause hearing loss.