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Monday, May 20, 2013
The ear and the middle ear conduct and transform sound; the inner ear receives it. When there is a problem in either the outer or middle ear, a conductive hearing impairment (loss of function) occurs. When the trouble lies in the inner ear, it causes a sensori-neural or nerve hearing impairment. Difficulty in both the middle and inner ear results in a mixed impairment.
A person with a conductive hearing impairment may notice that his ears seem to be full or plugged. He usually speaks softly because he hears his own voice very loudly. In general, his hearing is better in noise than in quiet. Crunchy foods, such as celery, sound very loud and he may have to stop chewing to be able to hear what is being said. With this type of impairment, one hears quite well over the telephone.
The patient with a conductive hearing impairment will be able to hear either with reconstructive ear surgery (otosclerosis) or by the use of a properly fitted hearing aid.
A sensori-neural hearing impairment may result from disturbance of inner ear circulation or fluid pressure or from disturbances of nerve transmission. The most common cause of sensori-neural impairment is an aging change in the nerve endings. This type of impairment is not surgically correctable but rarely leads to deafness.
The person with a nerve type of hearing impairment may be able to hear people talking, but not understand what they are saying. An increase in the loudness of speech may only add to her confusion. Her hearing is usually better in quite places and she may have difficulty hearing over the telephone. She will probably hear low tones better than high tones and, therefore, may find a man's voice more understandable than a woman's higher pitched voice. She may not hear a doorbell or the telephone ringing in another room.
When the impairment is sensori-neural, it is possible to restore some of this balance through the use of a hearing aid.
A hearing impairment in one ear takes away a person's ability to distinguish the direction of sound. He will also have difficulty hearing from the side of the impairment and may find it difficult to understand speech when there is background noise.
If you are experiencing a hearing problem, you should have a complete otologic examination by an ear specialist to determine the type of hearing problem and the appropriate treatment. If you have a hearing impairment, click here for tips on maintaining a high quality of life. If you would like information on interacting with people who have hearing impairments, click here.
Hearing-impaired individuals can prevent many potential communication problems with a properly fitted hearing aid in each ear. Some individuals will need additional help. There are some hearing impaired individuals who do not wish to wear hearing aids but do need help hearing the telephone, radio, television, doorbell, and alarm clock. Special communication assistive devices have been developed to solve many of these problems.
A number of people have trouble hearing important sounds of day-to-day life, like the telephone ringing, the doorbell chiming, the alarm clock, or the smoke detector. There are devices that can make any of these sound louder. There are also devices that substitute another sound, which is more easily heard, or that provide a visual or sensory cue. Specific examples are listed below:
Hearing impairment often affects perception of high frequencies. You may request that your telephone company provide you with an 805 Hz (low tone) bell on your telephone. Also, substitute a buzzer for the doorbell. Another alternative is to attach a system that activates a flashing light when the telephone or door bell rings.
A bedside lamp, a strobe light, a buzzer or a bed vibrator may be attached to an electric alarm clock. At the chosen time, the clock activates the alarm signal, which in turn causes the light to flash the buzzer to sound or the vibrator to move the bed frame, thus awakening the sleeper.
Several instruments are available to monitor smoke detectors or the cry of a baby in another room. An electronic switch can be installed to convert such sounds into something that can be seen or felt throughout the home.
Hearing aids may be worn as ear level instruments or as body-type aids. Ear level aids may be incorporated into the eyeglasses or may be worn in the back of the ear. There are also hearing aids that can be built into an ear mold and inserted entirely into the ear. As a general rule, body-worn hearing aids have greater amplifying potential and are used in cases of severe hearing impairment. Following are pictures of three ear level aids:
Hearing aids worn in both ears are called binaural hearing aids. There are a number of advantages to the use of aids in each ear. Binaural fitting will usually allow a patient to have balanced hearing, with speech heard equally loudly in the two ears. The most important advantage is that most hearing aid users are able to understand speech in a noisy background much better than when an aid is used in only one ear. Furthermore, using two aids results in a significant increase in the loudness of sound. The effect of this is that the volume control may be reduced for each ear and this in turn will lessen the impact of background noise. In many cases, hearing aids may be used to reduce ringing in the ears and other head noise, known as tinnitus. Hearing aid amplification may effectively mask tinnitus.
Each person reacts differently to the use of a hearing aid. Age, the severity of the hearing impairment, and the acceptance of the need for the aid, strongly influence how well a person adjusts to the use of a hearing aid. The type and degree of hearing impairment may limit the benefits to be gained from a hearing aid. Generally speaking, the hard of hearing person has a double challenge. He experiences a reduction in the normal loudness, as well as an accompanying reduction in what is called discrimination. Discrimination refers to one's ability to distinguish among the sounds that one hears. A discrimination impairment leads to a reduction in understanding.
If a person has an impairment of the conductive type, he can expect maximum benefits from a hearing aid because discrimination ability is not greatly affected. Most persons with this type of impairment become adjusted to using a hearing aid with very little difficulty.
If the hearing impairment is of the sensori-neural or nerve type, there may be greater difficulty adjusting to a hearing aid. Very often, persons who have this type of loss can hear speech sounds if they are loud enough, but cannot always understand what is being said. It is true that speech must be loud enough to permit the listener to understand to his full capability. However, making speech increasingly louder will not necessarily lead to an improvement in discrimination because the hearing nerve has become less sensitive to differences of speech sounds. A hearing-impaired person will often say, "I hear, but I can't always understand what I hear." Because the prime function of an aid is to amplify sounds, some users of these instruments continue to experience difficulty in understanding. Through amplification, some sounds of speech can be heard and understood with greater ease. The hearing aid offers the user hearing that is short of normal but more satisfactory than unaided hearing.
The major problem for a hearing aid user is to adjust the hearing aid when there is noise. There have been many innovations in hearing aid fitting that have helped new users to learn to live with noise. Changes in circuitry of the hearing aid, specially designed ear molds, and highly adjustable aids have greatly eased the process for many patients.
Whatever the type of hearing impairment, it is important to follow a planned program of learning to use the hearing aid. The ease or difficulty of hearing will vary depending on the loudness of background noises, the distance of the listener from the source of sounds, the clarity of speech or music, and the lighting (which can either help or interfere with lip reading). Practice exercises will help to prepare the wearer to use his hearing aid in widely different situations.
Some people cannot hear speech even with the most powerful hearing aids. Fortunately, a scientific advancement called the cochlear implant now allows a totally deaf person to hear sound. The cochlear implant is an electronic instrument. Part of the device is implanted in the temporal (ear) bone and the other part works like a pocket-type hearing aid (worn on the body). The cochlear implant, however, is not a hearing aid. It allows very limited speech discrimination (understanding), makes communication easier, and enables the user to hear many environmental sounds.
A thorough evaluation is required to determine if a person with severe hearing loss is suitable for the implant. Since 1982, more than 25,000 cochlear implants have been performed worldwide. A cochlear implant may not be the best choice for everyone. There are many factors to consider in making your decision.
The length of time between the microphone picking up a sound and the brain receiving the information is very short, so the implant user hears sounds as they occur.
Last Reviewed: Mar 24, 2006
David L Steward, MD
Professor of Otolaryngology
College of Medicine
University of Cincinnati