How Does Hearing Work?
The ear has three parts: the external ear (or pinna and ear canal), the middle ear, and the inner ear. Each part of the ear has a role in hearing.
The external ear gathers sound waves and transmits them to the eardrum. The eardrum is a membrane between the outer and middle ear. The sounds waves produce vibrations of the eardrum which are then transmitted to the first bone of the middle ear, the malleus (hammer). The sound waves are amplified as they are passed from the eardrum and malleus to the next two bones of hearing, the incus (anvil) and stapes (stirrup).
Once the sound waves have reached the stapes sound has been converted from an air pressure wave to a mechanical force. The stapes rests on a thin membrane separating the middle ear from the fluid-filled inner ear. As the stapes vibrates, sound waves are transformed into fluid waves in the inner ear.
The inner ear contains fragile membranes, hair cells and nerve endings. The fluid waves and movement of the membranes stimulate the hair cells, which then activate the nerve endings. Finally the electrical signal of hearing travels along the cochlear (hearing) nerve to the brain and the sound is "heard".
Types of Hearing Impairment
Conductive Hearing Loss usually results from conditions of the external or middle ear, although there are a few very unusual causes of inner ear-related conductive hearing loss. Perforations (holes) of the eardrum, middle ear infection or inflammation, otosclerosis, and trauma are potential sources of conductive hearing loss. This type of hearing loss may be surgically correctable. Hearing aids are also very effective in these patients. The specific cause of a conductive hearing loss can be determined by a physician trained in the evaluation of the ear, such as an Ear Nose and Throat doctor (Otolaryngologist) or an otologist/neurotologist.
Sensorineural Hearing Loss is a result of injury, inflammation, or aging of the inner ear, the hearing nerve, or the brain. The most common cause of hearing loss is presbycusis or age-related hearing loss. Many congenital and hereditary hearing losses are sensorineural. Other causes include trauma, noise exposure, idiopathic sudden hearing loss, Meniere's disease, acoustic neuroma tumors, autoimmune inner ear disease, and Lyme disease. Sensorineural hearing loss includes a loss of loudness of sound and/or a decline in the understanding of speech. High pitched sounds are often lost first, followed by a gradual loss of low tones. This type of hearing loss may be sudden or slowly progressive.
Diagnosis of the specific cause of sensorineural hearing loss requires an examination by a qualified physician, high quality hearing testing, review of family and medical history, and possibly radiographic imaging such as MRI or CT scans. Many kinds of sensorineural hearing losses can be treated medically if a diagnosis is made in a timely manner. Surgery is generally not effective in returning normal hearing. Hearing aids are beneficial for most patients. New technology including implantable hearing aids and cochlear implantation are available for patients who do not do well with hearing aids.
Mixed Hearing Loss is a combination of conductive and sensorineural hearing loss. It is often a combination of two or more conditions of the ear. It should be evaluated by a physician, and may require a combination of treatments, including surgery and/or hearing aids.
Hearing Loss in One Ear
A hearing loss isolated to one ear results in a unique but frustrating experience for the patient. Even a small hearing loss decreases a person's ability to distinguish the direction of sound and understand speech in noisy backgrounds. More severe one-sided hearing loss will not only affect the hearing in the affected ear alone, but also results in significant difficulty of understanding speech in background noise, such as an office, a party, or even a restaurant. The patient will not be able to discriminate sound from the left side versus the right side. He may require face-to-face conversation and may even read lips in order to better communicate.
What is Tinnitus?
Tinnitus is noise in the ear or head. Tinnitus is often associated with hearing loss and results from the same mechanisms that cause hearing loss.
How is Hearing Loss Evaluated?
The evaluation of hearing loss includes a physical examination of the ear, nose and throat. An otologist/neurotologist will examine the ears with a microscope to clean the ears and observe in detail the ear canal, the eardrum, and the status of the middle ear.
An audiologist (non-physician hearing care professional) will perform an audiogram (hearing test), which will include pure tone hearing levels and speech understanding. Tone hearing is tested through the air (air conduction) and through the mastoid bone (bone conduction). All three components of the audiogram are important in determining the type. For example, if air and bone conduction thresholds are the same, the loss is sensorineural. If there is a difference between air and bone thresholds (an air-bone gap), the loss is conductive or mixed. Specific information is also important in making a diagnosis of the cause of the hearing loss. It is important for the audiogram to be personally reviewed by a physician. Several important signals should be brought to the prompt attention of a doctor including:
- Asymmetric hearing loss
- Progressive hearing loss
- Sudden hearing loss
- A painful or draining ear
- A lesion of the external ear
- Difficulty hearing despite a normal hearing test
- Tinnitus (head or ear noise)
- Dizziness, vertigo, or balance difficulty
- Excessive ear wax
- A medical history of cancer
- Pain with loud sounds
Hints for Hearing Better
There are many simple things a patient and his/her family may do to improve hearing and communication.
Hints for the Patient:
- Ask friends and family to get your attention first before talking.
- Watch the face and lips closely for lip movements, facial expressions and gestures. This will help you distinguish consonants, content, and mood of the speech.
- Don't just nod agreeably if you don't understand. Try repeating what was said if you aren't sure. Your family will appreciate a second chance.
- Don't say "Huh? or What?" Instead say, "I didn't understand you". This will encourage the speaker to pay more attention to you, change words, and perhaps speak more clearly.
- Don't be afraid to participate in active conversations. Pay attention to changes in speakers and watch their faces carefully. If the light is poor or the background noise is too loud, do what you can to change the environment.
- Consider speech reading classes.
Hints for Family and Friends of a Hearing-Impaired Person:
- Get the person's attention before you initiate a conversation.
- Do not try to talk to the person from another room.
- Position yourself 4 to 6 feet away in good light.
- Make sure the person can see your face and mouth. Do not cover your mouth or try to talk while chewing.
- Turn down background noise such as the TV or stereo.
- Speak at a normal rate.
- Enunciate your words carefully and pause slightly between words and phrases.
- Repeat what you said and/or restate what was said in a different way.
- Do not yell in the person's ear. Not only does this distort the sound and prohibit the person from reading your speech, but it also suggests frustration and anger. Loud sound can be very painful to a person with hearing loss.
- Try not to drop off your volume or tone at the end of sentences.
Hearing Aids and Other Devices for Hearing Loss
There are many devices available for the management of hearing loss. The decision on which device is best for an individual's specific needs should be determined by the patient, with the advice of a physician and an audiologist. When hearing loss is present in both ears and the doctor and audiologist recommend two hearing aids, many patients wonder whether this is necessary. There are several advantages to wearing a hearing aid in both hearing-impaired ears.
Federal regulation prohibits any hearing aid sale unless the buyer has first received a medical evaluation from a physician. An otolaryngologist, audiologist, or an independent dispenser can dispense aids. Hearing aids should be custom fitted and for each individual's hearing needs. Hearing aids purchased by mail-order typically cannot be custom fitted. It is also important to purchase a hearing aid from a professional to whom the patient will have easy access for follow-up visits and supplies.
Cochlear implants are available for patients with sensorineural hearing loss not adequately treated with hearing aids.
Other Hearing Assistive Devices:
- Telephone amplifiers for both land lines and cell phones
- Infrared systems for TV and theaters
- FM systems
- Devices for monitoring of smoke detectors, telephone and door bells, and alarms
- Implantable hearing aids
- Bone anchored hearing aids
It is important for every person with hearing loss to be evaluated by a physician experienced in the evaluation and treatment of hearing loss, such as an otolaryngologist or otologist/neurotologist
For more information visit the Better Hearing Institute Web site
If you would like to make an appointment or talk to an Audiologist, please call the Hearing and Balance Center at 410-328-5947.