Lisa sat quietly in the classroom not participating in conversations around her. Her teacher originally thought Lisa was shy, until one day he was talking to her and she did not respond. A hearing test showed a significant hearing loss to where she was unable to recognize sounds and language. That explained a lot. Luckily for Lisa, her teacher noticed and her difficulties could be addressed with assistive technology. (Unfortunately, too many students like Lisa remain undiagnosed.)
To understand assistive technologies, it is useful to know a little about sound. Sound is measured in two ways: by its loudness or intensity (measured in units called decibels, dB) and its frequency or pitch (measured in units called hertz, Hz). Impairments in hearing can occur in either or both areas, and may exist in only one ear or in both ears. Hearing loss is generally described as slight, mild, moderate, severe, or profound, depending upon how well a person can hear the intensities or frequencies most greatly associated with speech. Generally, only people whose hearing loss is greater than 90 dB are considered deaf.
Types of Hearing Loss
Physiologically speaking, hearing loss is classified into two categories. Conductive hearing losses are caused by diseases or obstructions in the outer or middle ear (the conduction pathways for sound to reach the inner ear). Conductive hearing losses usually affect all frequencies of hearing evenly and do not result in severe losses. A person with a conductive hearing loss is usually well-served with a hearing aid or can be helped medically or surgically.
Sensorineural hearing losses result from damage to the delicate sensory hair cells of the inner ear or the nerves which supply them. These hearing losses can range from mild to profound. They often affect the person’s ability to hear certain frequencies more than others. Thus, even with amplification to increase the sound level, a person with a sensorineural hearing loss may perceive distorted sounds, sometimes making the successful use of a hearing aid impossible.
A 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 the inner ear. A central hearing loss results from damage or impairment to the nerves or nuclei of the central nervous system, either in the pathways to the brain or in the brain itself.
Lisa’s diagnosis was a conductive hearing loss resulting from reoccurring untreated ear infections. Lisa worked with audiologists and doctors to find ways for her to interact more successfully in the classroom. One audiologist suggested she use an Assistive Listening Device that amplified the speech of the teacher directly into her new digital hearing aid. It did the trick and soon Lisa began laughing with her classmates.
Accommodations and assis-tive devices are required by many people with hearing impairment to access the educational programming in a classroom setting, communicate with others and work effectively with coworkers. Each person’s needs must be individually evaluated, but the following is a generic introduction to the main types of assistive technology for people with hearing impairments.
Assistive Listening Devices
Assistive listening devices include a large variety of technologies designed to improve audibility in specific listening situations. Some are designed to be used with hearing aids or cochlear implants, while others are designed to be used alone. Many that are used in conjunction with hearing aids require a telecoil (T-switch).
Assistive listening devices can usually amplify a signal, but their primary purpose isn’t to make a signal louder. Rather, they place a microphone close to the sound source, so that it becomes louder compared to the other sounds in the environment. Assistive listening devices improve the ability to hear because they make the desired sound stand out from the background noise.
Closed captioning is the text that goes on the bottom of the television screen to inform deaf or hard of hearing people of what is being said. Look for a small box with letters “CC” inside of a small box with a cartoon balloon dialogue marker, to verify if the programs are closed captioned.
A cochlear implant is used for people with severe to profound hearing loss or those who show little or no benefit from hearing aids, yet have some hair follicles. It is a controversial device, especially when it is implanted in young children. This very tiny piece of electronic equipment is put into the cochlea during an operation. It takes over the job of the damaged or destroyed hair cells in the cochlea by turning sounds into electrical signals that stimulate the hearing nerve directly.
Hearing aids are similar to tiny microphones—they help someone hear sounds better through amplification. Hearing aids deliver amplified sounds (via sound vibrations) from the eardrum and middle ear to the inner ear or cochlea. Hearing aid technology is available that can adjust the volume of sounds
A Hearing Loop is a coil of wire that amplifies sound and reduces background noise. Users of hearing aids with a loop can set their aids to a certain setting to receive the transmission. Hearing loops can be permanently installed or portable.
Text Telephones (TTYs) are one communication option for people who are deaf or hard of hearing. These devices look like small typewriters and come with an LCD screen and a cradle for the telephone. In order for a person to call on the TTY, the person on the other end must also have a TTY. There is also a national relay system which allows the person on the TTY to call someone who does not have a TTY. They system also allows people using mobile phones and pagers to send emails, faxes, pages and call people who have TTY.
Visual Alert Signalers
Visual Alert Signalers are devices that use flashing lights to alert the person who is hard of hearing or deaf to the ringing of a phone or fire alarm or other device.
The above list is only a sample. There are many more assistive technology devices available for people who are hard of hearing. Many of these devices—such as text messaging and e-mail—have infiltrated mainstream society. You can find out more by researching the topic on the Internet. There are excellent Web sites explaining how the technologies work, how to have them evaluated, and where to buy them.