Overview of Hearing & Screening
Hearing is the ability to perceive or the act of perceiving sound. It is a complex process that involves the ears and the nervous system (e.g., nerves, brain). More than 200 conditions have been identified that can affect hearing and result in hearing impairment, deafness, or hearing loss.
Hearing disorders may result in partial hearing loss or the complete inability to hear. The term "hearing impairment" refers to a condition in which a person's ability to hear is reduced significantly so that it is noticeable to the person or to others.
Hearing impairment can be present at birth (congenital) or can develop at any age (acquired). Because hearing is vital for speech development, it is important to diagnose hearing disorders as early as possible in young children. Early intervention can help improve function in people who are hearing impaired.
Hearing loss is one of the most common sensory disorders. As many as 10 percent of adults have some degree of hearing loss and about 35 percent of people over the age of 65 have significant hearing loss. In most cases, hearing loss can be successfully treated using hearing aids.
According to our sister publication Diabetes Focus Spring 2013, recent studies have found that adults with diabetes are more likely to have a hearing impairment than adults without the condition, possibly as a result of damage to nerve endings in the ear. If you have diabetes, it's important to have your hearing tested at least once a year to detect hearing loss as early as possible.
Anatomy & Hearing
Hearing occurs as a result of the transfer of sound waves (called conduction) through the auditory system. The outer ear (pinna or auricle) collects sound waves that travel through the air and transmits them to the middle ear through the ear canal (also called the auditory canal).
The outer ear is separated from the middle ear by the eardrum, also called the tympanic membrane, which is a thin piece of tightly-pulled skin. When sound waves reach the eardrum, they cause the membrane to vibrate, transmitting the waves to the middle ear.
The middle ear is connected to the back of the nose through the eustachian tube. It consists of three tiny bones called the ossicles. These bones include the malleus, the incus, and the stapes, which are Latin words that mean "hammer," "anvil," and "stirrup." The ossicles transfer sound waves as vibrations into the fluid-filled inner ear (also called the labyrinth).
The fluid-filled inner ear is involved in hearing and also in balance. It contains the cochlea, which is a small, coiled tube that is lined with tiny hair-like cells, and nerves. As the stapes vibrates, it causes pressure changes in the inner ear fluid and pushes back and forth against the cochlea.
Sensitive cells in the cochlea generate nerve signals that travel through the cochlear nerve to the brainstem. The cochlear nerve is a branch of the auditory nerve, also called the eighth cranial nerve. The brain then interprets these nerve signals as sound.