Deafness and Hardness of Hearing Fact Sheet
What we refer to as the "hearing system" actually consists of at least three subsystems; the outer ear, middle ear, and inner ear. The ear we can see and the auditory canal compose the outer ear. The middle ear contains the eardrum and the hammer and anvil, and the inner ear contains the cochlea. Sound waves enter the ear, pass through the auditory canal, strike the eardrum, pass through the hammer and anvil, and are carried to the brain by the cochlea.
There are four different types of hearing loss; each has different causes and varies by degree or severity.
- Conductive hearing loss is caused by damage to the outer or middle ear. Causes may include: infection, punctures, obstructions, hardening of the calcium in the bones in the middle ear, accidents of birth, or heredity.
- Sensorineural hearing loss, also known as "nerve deafness," occurs in the inner ear and may result from aging, accidents of birth, various infections, fluid buildup, exposure to loud noise, or heredity.
- Mixed hearing loss refers to a combination of conductive and sensorineural loss and means that a problem occurs in both the outer or middle and inner ear.
- Central hearing loss results from damage to the nerves of the central nervous system, either in the path to the brain or in the brain itself.
Hearing loss may be temporary or permanent, but always affects people differently. People often experience hearing loss in terms of reduced sensation, changes in frequency, or additional environmental noise. Most people experience some reduction in hearing as they age.
Hard of Hearing. Functionally, a person who is hard of hearing uses residual hearing, and he or she usually benefits from amplification, auditory training, or speech reading, otherwise known as "lip reading." Most people have difficulty mastering lip reading. While lip reading skills can help in communication, only about 30% of all speech is visible on the lips. Try some lip reading to experience the difficulty first hand.
If the hearing loss is more severe, the person may benefit from hearing aids and a variety of assistive listening devices (ALDs). Based on the age of onset of hearing loss, people respond differently. Elders that experience hearing loss have different expectations than those that lose their hearing early in life.
Deaf. There are two types of deafness: pre-lingual deafness describes a person who is born deaf or becomes deaf prior to language development; and post-lingual deafness, which describes a person that becomes deaf later in life, after speech and language have developed. People who are deaf do not rely on auditory means for communication. They may use sign language and sign language interpreters for communication. The language a deaf person uses depends on the environment. Just as a hearing child growing up in an English-speaking family will use English, a deaf person uses the language he or she learned from people in their environment. This may be American Sign Language (ASL), manually coded English, speech or lip reading, or combinations of all these.
According to the National Center for Hearing Assessment and Management (http://www.infanthearing.org), one in every ten Americans (28 million) has hearing loss. As the baby boomers age, this number is expected to rise dramatically, nearly doubling by the year 2030. Among elders, hearing loss is the third most prevalent disabling condition behind arthritis and hypertension. Elders that become deaf later in life (post-lingual) typically do not learn sign languages.
Cultural and Social Contexts
Organizations. Locate and review the following organizational websites to learn more about the current issues in the hard of hearing and deaf communities.
- Self Help for Hard of Hearing (http://www.hearingloss.org)
- National Association of the Deaf (http://www.nad.org)
- World Federation of the Deaf (http://www.wfdeaf.org)
- Telecommunications for the Deaf (http://www.tdi-online.org/tdi/orgnization.asp)
- Hearing Industries Association (http://www.hearing.org)
Sign Languages. As was mentioned earlier, some people who are deaf use sign language for communication, and sign language is an important part of deaf culture. American Sign Language (ASL) is one such language. ASL is deeply rooted in deaf community and culture. ASL is a visual language with its own grammar (rules), syntax (order), semantics (meaning) and lexicon (vocabulary). At least 35 states recognize ASL as a modern language for public schools. Hundreds of colleges and universities offer ASL classes, and the American Sign Language Teachers Association (ASLTA) certifies ASL teachers (see http://www.ASLTA.org for more information).
Cochlear Implants. A cochlear implant is a surgically implanted electronic device that allows people with significant hearing loss, who do not obtain much benefit from hearing aids, to hear. Children as young as twelve months of age with profound hearing loss (greater than 90 decibels) in both ears, as well as adults with severe-to-profound hearing loss (70 decibels or greater) who receive no benefit from hearing aids, are candidates for a cochlear implant. The cochlear implant has an internal portion that is placed under the skin above and behind the ear. An electrode array is inserted into the inner ear. The external portion of the device is a mini-computer called a sound processor that translates sounds into signals, which are then sent to the hearing nerves and are recognized by the brain as sound. The sound processor captures sounds from the environment and translates them into digital information. This digital information is then transmitted to the implant. The implant converts the digital information into signals that are sent via the implanted electrodes, directly to the hearing nerve. The hearing nerve sends the information to the brain, where it is heard.
There are an estimated 25,000 cochlear implant (CI) users in the United States, and approximately 78,000 worldwide. While cochlear implants are not without controversy in the deaf community, successful outcomes from the procedure are beginning to be reported (e.g., the majority of CI users are able to use voice telephones), and CI users themselves report being able to comprehend up to 90% of the words in sentences without speech reading. (For more details, see marketing materials disseminated by Cochlear Americas and Advanced Bionics, two of the largest CI companies in the world today.)
Tips for One-on-One Interaction. First, get the individual's attention. Cue the deaf person about the topic of conversation. Speak clearly, look at the person and maintain eye contact. Don't turn away and continue speaking and don't place anything over your mouth while speaking. Turn down audio and video sources and reduce background noise. Use pantomime, body language, and facial expression. Point to assist in communication. Remember to take time to communicate.
Consider also that deaf adults live and function in a majority-hearing world and routinely miss information. Even the best lip reader loses information when the speaker turns away and continues talking. Remember that it's important to let people who are deaf speak for themselves, but not to make them representatives of the deaf community.
Hearing Aids. Hearing aids are used widely by people with hearing loss and are effective for about 95% of users. Hearing aids differ in design, type of circuitry, size, and amount of amplification, but do have similar components, include a microphone, amplifier, receiver and batteries. Only 30% of hearing aids are equipped with an option called a telecoil, which allows users to directly "couple" the hearing aid with compatible telephones and assistive listening devices. This coupling improves the intelligibility of sound in noisy environments, in poor acoustical environments, and when the speaker is at a distance from the user.
Assistive Listening Devices. Assistive listening devices (ALDs) may benefit people with residual hearing. About 1 in 4 use telephone amplifiers, while about 10% use some amplification for listening to TV, movies, church services, and conferences. All three types of wireless ALDs (audioloop, FM, and infrared) augment standard public address and audio systems by providing signals that can be received by special receivers or hearing aids. Technically, ALDs increase the signal-to-noise ratio (SNR). The SNR must be higher for people with hearing loss to hear speech over background noise, reduce the "distance" between the person and speaker, enhance poor acoustics, and reduce background noise. ALDs are examples of auxiliary aids, services, and reasonable accommodations required by the Americans with Disabilities Act (ADA). Public facilities, state and local governments, and employers are required to provide these types of ALDs to enable people to participate in their programs and services. Most ALDs must be purchased through a hearing-health professional, by mail order or via the World Wide Web from ALD distributors. Other assistive technology devices link audible and visual signals and/or tactile feedback to assist users. These devices include smoke detectors, doorbells, telephone ring signalers, specially equipped telephones, and alarm clocks. Captioning and computer-assisted real-time transcription (CART) provide access to multimedia.
Telephones and Telecom Services. Many deaf and hard of hearing people use teletypewriters (TTYs) to communicate by text over regular telephone lines. Hearing people and those without TTYs can use Telecommunications Relay Services (TRS). TRS allows anyone with speech or hearing loss to communicate with almost anyone in the world using the telephone. TRS can be used to communicate with TTY users. Telecommunications companies, who provide telephone services to homes and offices, provide TRS at no additional charge.
Prevalence of Deafness and Hard of Hearing
9.3 million Americans have a sensory disability involving sight or hearing. (Source: Waldrop J. & Stern, S.M. Disability status 2000; Census 2000 brief. March 2003, U.S. Department of Commerce, Economics and Statistics Administration, U.S. CENSUS BUREAU.)
About 8.0 million Americans have difficulty hearing what is said in a normal conversation with another person (even when wearing a hearing aid); of these, 800,000 were unable to hear what was said in a normal conversation. (Source: McNeil, J. Americans with disabilities: Household economic studies. February 2001, U.S. Department of Commerce, Economics and Statistics Administration, U.S. CENSUS BUREAU.)