Hearing loss is the third most common medical condition in the United States, affecting around 20% of Americans. Continue reading to learn more about hearing loss, including how the ear works and types of hearing loss - information provided by our Doctor of Audiology, Eleanor Wilson Au.D.
The ear consists of three main parts:
The visible portion of your outer ear is called the pinna. The noises you hear in your daily life collect as sound waves and are channeled into the ear canal where the sound is amplified. The sound waves then travel toward a flexible, oval membrane at the end of the ear canal called the tympanic membrane (eardrum). When these waves reach your eardrum it begins to vibrate.
The vibrations from the eardrum set the ossicles into motion. The ossicles are the three tiny bones that are the smallest in the human body and are known as the malleus (hammer), incus (anvil), and stapes (stirrup). They all work together to further amplify and transmit the sound to your inner ear.
The stapes attaches to the oval window that which is a membrane-covered opening that leads from the middle ear to the inner ear. The eustachian tube connects the middle ear to the nasopharynx and is responsible for equalizing the air pressure between the the middle ear and your environment.
The sound waves enter the inner ear into a snail-shaped organ called the cochlea. The cochlea is filled with fluids that move in response to the vibrations from the oval window. As the fluid moves, thousands of nerve endings are set into motion and transform the vibrations into electrical impulses. These impulses travel along the auditory nerve to the brain.
The brain then interprets these signals and this is how we hear and understand. The inner ear also contains the vestibular organs that are responsible for balance.
Conductive hearing loss is a problem in the outer or middle ear that prevents sound from reaching the inner ear. Many times, conductive hearing losses are temporary and can be treated with medical intervention.
Some possible causes of conductive hearing loss are:
Sensorineural hearing loss is the result of a problem in the inner ear and occurs when nerve fibers in the cochlea are missing or damaged. The nerve fibers are known as the outer and inner hair cells, and they are responsible for transmitting signals to the brain which allows one to hear and interpret sound.
Some possible causes of sensorineural hearing loss are:
Sometimes a conductive hearing loss occurs in combination with a sensorineural hearing loss. When there is damage to the outer or middle ear and the inner ear or auditory nerve, a mixed hearing loss is diagnosed.
It is very common to explain the degree of hearing loss by describing it as mild, moderate, severe and profound with some professionals also adding the term moderately-severe.
It is less common to provide a percentage describing the degree of hearing loss unless the professional who provides that information can explain how the percentage was determined.
A percentage based on the Articulation Index (AI) is based on research and calculates how much phonemic information (speech sounds) can be heard by the patient with more commonly used speech sounds such as the “s” given more weight compared to a relatively uncommon speech sound such as the “th” in feather.
Hearing loss is commonly described as the inability to hear softer sounds but based on the degree of hearing loss, the ability to interpret frequencies accurately and hear loudness correctly is also impacted.