The Science of Bone Conduction
SoundBite™ is a bone conduction prosthetic hearing device. Prosthetic hearing devices produce the perception of sound by replacing the function of the middle ear, cochlea, or auditory nerve. As long as one cochlea is functional, SoundBite Hearing System allows sound to travel via the teeth, through the bones, to the functioning cochlea, bypassing the middle and outer ear entirely. By using bone conduction via the teeth, SoundBite is intended to help patients who suffer from Single Sided Deafness or Conductive Hearing Loss rejoin the conversation of life, all without surgery.
What is a cochlear implant?
Ear with cochlear implant.
Credit: NIH Medical Arts
Credit: NIH Medical Arts
A cochlear implant is a small, complex electronic device that can help to provide a sense of sound to a person who is profoundly deaf or severely hard-of-hearing. The implant consists of an external portion that sits behind the ear and a second portion that is surgically placed under the skin (see figure). An implant has the following parts:
- A microphone, which picks up sound from the environment.
- A speech processor, which selects and arranges sounds picked up by the microphone.
- A transmitter and receiver/stimulator, which receive signals from the speech processor and convert them into electric impulses.
- An electrode array, which is a group of electrodes that collects the impulses from the stimulator and sends them to different regions of the auditory nerve.
An implant does not restore normal hearing. Instead, it can give a deaf person a useful representation of sounds in the environment and help him or her to understand speech.
How does a cochlear implant work?
A cochlear implant is very different from a hearing aid. Hearing aids amplify sounds so they may be detected by damaged ears. Cochlear implants bypass damaged portions of the ear and directly stimulate the auditory nerve. Signals generated by the implant are sent by way of the auditory nerve to the brain, which recognizes the signals as sound. Hearing through a cochlear implant is different from normal hearing and takes time to learn or relearn. However, it allows many people to recognize warning signals, understand other sounds in the environment, and enjoy a conversation in person or by telephone.
Who gets cochlear implants?
Credit: Centers for
Disease Control and
Prevention (CDC)
Disease Control and
Prevention (CDC)
Children and adults who are deaf or severely hard-of-hearing can be fitted for cochlear implants. According to the Food and Drug Administration (FDA), as of December 2012, approximately 324,200 people worldwide have received implants. In the United States, roughly 58,000 adults and 38,000 children have received them.
Since 2000, cochlear implants have been FDA-approved for use in eligible children beginning at 12 months of age. For young children who are deaf or severely hard-of-hearing, implantation while young exposes them to sounds during an optimal period to develop speech and language skills. A growing body of research, much of it funded by the NIDCD, has shown that when these children receive a cochlear implant followed by intensive therapy before 18 months of age, they are better able to hear, comprehend sound and music, and speak than their peers who receive implants when they are older. Studies have also shown that eligible children who receive a cochlear implant at a young age develop language skills at a rate comparable to children with normal hearing, and many succeed in mainstream classrooms.
Some adults who have lost all or most of their hearing later in life can also benefit from cochlear implants. They learn to associate the signal provided by an implant with sounds they remember. This often provides these individuals with the ability to understand speech solely by listening through the implant, without requiring any visual cues such as those provided by lipreading or sign language.
How does someone receive a cochlear implant?
Use of a cochlear implant requires both a surgical procedure and significant therapy to learn or relearn the sense of hearing. Not everyone performs at the same level with this device. The decision to receive an implant should involve discussions with medical specialists, including an experienced cochlear-implant surgeon. The process can be expensive. For example, a person’s health insurance may cover the expense, but not always. Some individuals may choose not to have a cochlear implant for a variety of personal reasons. Surgical implantations are almost always safe, although complications are a risk factor, just as with any kind of surgery. An additional consideration is learning to interpret the sounds created by an implant. This process takes time and practice. Speech-language pathologists and audiologists are frequently involved in this learning process. Prior to implantation, all of these factors need to be considered.
What does the future hold for cochlear implants?
With advancements in technology and continued follow-up studies with people who already have received implants, researchers are evaluating how cochlear implants might be used for other types of hearing loss.
NIDCD is supporting research to improve upon the benefits provided by cochlear implants. It may be possible to use a shortened electrode array, inserted into a portion of the cochlea, for individuals whose hearing loss is limited to the higher frequencies. Other studies are exploring ways to make a cochlear implant convey the sounds of speech more clearly. Researchers also are looking at the potential benefits of pairing a cochlear implant in one ear with either another cochlear implant or a hearing aid in the other ear.
Where can I get more information?
The NIDCD maintains a directory of organizations that provide information on the normal and disordered processes of hearing, balance, smell, taste, voice, speech, and language. Please see the list of organizations at www.nidcd.nih.gov/directory.
Use the following keywords to help you search for organizations that can answer questions and provide printed or electronic information on cochlear implants:
For more information, additional addresses and phone numbers, or a printed list of organizations, contact:
NIDCD Information Clearinghouse1 Communication Avenue
Bethesda, MD 20892-3456
Toll-free Voice: (800) 241-1044
Toll-free TTY: (800) 241-1055
Fax: (301) 770-8977
E-mail: nidcdinfo@nidcd.nih.gov
NIH Publication No. 11-4798
Statistics Updated November 2013
Partial Update August 2014
Statistics Updated November 2013
Partial Update August 2014
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