Hearing impairment is an umbrella term covering all types and degree of hearing loss, those that are considered as deaf and those regarded as hard of hearing. The U.S. Education Department defines hearing loss "a hearing impairment that is so severe that the child is impaired in processing linguistic information through hearing, with or without amplification, that adversely affects a child's educational performance". While, The Individuals with Disabilities Education Act (IDEA) defines hearing loss as "hearing impairment whether permanent or not, that affects a child's educational performance. This definition includes children who have the capacity to receive some auditory stimuli, including speech and language; this capacity is known as residual hearing, which can be supported by the use of a hearing aid". On other hand, "hearing loss/impairment results when the hearing apparatus is damage or limited in its function to such an extent that sounds cannot be perceived or understood".
Types of Hearing Loss
I- Conductive Hearing Loss
Conductive hearing loss is caused by a problem in the outer or middle ear, including eustachian tube malfunction or a defect in the ossicular chain. In most cases, conductive hearing loss affects the lower frequencies and makes it difficult for the ear to hear vowel sounds and interpret the slight differences among them. Since vowels contain the "power of speech" the person perceives speech and other sounds as being much "quieter" than normal. If the sound is loud enough, a person with a conductive hearing can hear and understand clearly. Conductive hearing loss can often be medically treated. If a conductive hearing loss is not treated, it can sometimes lead to permanent damage of the inner ear.
II- Sensorineural Hearing Loss
Sensorineural hearing loss is the most common type of hearing loss and is caused by damage to the inner ear and/or the auditory nerve. Noise exposure, diseases, certain medications and aging can destroy part of the inner ear and cause permanent hearing loss. Once damage, the inner ear cannot be repaired. A "cochlear implant" is available for some who have a profound hearing loss and do not gain benefit from conventional hearing aids. With sensorineural hearing loss, the entire cochlear is seldom damaged. If a sound is loud enough, a person with inner ear damage may hear something. The undamaged parts of the cochlear transmit sound to the auditory nerve and on to the brain; however, the sound may be distorted. Distortion occurs when the cochlear changes the sound in some way. Sensorineural hearing loss is also characterized by a lower tolerance to loud sounds. Sensorineural hearing loss usually affects the high frequencies the most, which impairs a person's ability to differentiate consonant sounds.
Mixed Hearing Loss
When a person has both a conductive hearing loss and a sensorineural hearing loss, it is called a mixed hearing loss. For example, if a child who has a permanent sensorineural hearing loss gets a middle ear infection, the affects of the two types of hearing loss combine to create a greater hearing loss. In a nutshell, mixed hearing loss refers to simultaneous existence of a conductive hearing loss and a sensorineural hearing loss. That is, a condition where both the conductive as well as the inner part of the ear are impaired.
Retro-Cochlear Hearing Loss
When a person has a sensorineural hearing loss, particularly a unilateral hearing loss, the problem may be beyond the inner ear, somewhere in the brainstem. An acoustic rumor may be involved and may lie on the auditory nerve, brainstem or in the brain. Surgical intervention is most often warranted. Retro-cochlear hearing loss is noted by inconsistencies in the audiogram, such as poorer speech recognition ability than the pure tones indicate, especially at loud presentation levels.
Degree of Hearing Loss
The degree of hearing loss refers to the severity of the loss in hearing. The World Health Organization (W.H.O) gave five categories of degree of hearing loss. They are presented below:
i. Mild hearing loss (21 – 40 dB): only speech that is soft or produced at a distance is difficult to hear or understand.
ii. Moderate hearing loss (41 – 55 dB): typically conversational speech is hard to follow.
iii. Moderately severe hearing loss (56 – 70 dB): only loud speech can be heard
iv. Severe hearing loss (71 – 90 dB): loud speech is hard to understand.
v. Profound hearing loss (91 dB+): hearing aids may help understanding words. Additional rehabilitation needed. Lip-reading and sometimes signing essential.
Classification of Hearing Impairment
Hearing impairment is an umbrella term which covers both the deaf and the hard of hearing. Therefore, persons with hearing impairment are classified into deaf and hard of hearing.
i. Deafness: deafness can be seen as loss of "sound/ hearing" sensitivity that renders a person's hearing non-functional for day-to-day purpose of life including the reception of speech and language with or without hearing aid. The deaf are persons whose auditory channel (ear) is significantly damaged/defective, rendering the person's sense of hearing non-functional with or without hearing aid for the ordinary purpose of life.
ii. Hard of Hearing: hard of hearing can be described as those who have residual hearing. Persons who are hard of hearing can process information from sound usually with the help of a hearing aid. They have mild to moderate hearing loss. In a nutshell, hard of hearing are those who have lost some but not all of their hearing, and who can benefit from the use of hearing aids in order to understand the use of speech.
Age of Onset of Hearing Impairment
1- Congenital Hearing Impairment: congenital hearing impairment means hearing defect in persons who are born with non-functional hearing. It is the type in which the person is born deaf, and will not be able to develop any language and speech naturally.
Adventitious Hearing Impairment: adventitious hearing impairment means hearing defect in persons who are born with normal hearing but later in life the sense of hearing become a non-functional as a result of illness or accident. It is a situation in which the child is born normal but, become a deaf or hard of hearing later in life as a result of ignorance, sickness, accident, diseases, carelessness, trauma, side-effect of a medicine, hearing loss is gradual, and often detected by teachers, family members and friends.
Classification of Hearing Impairment Based on Language Development
1- Pre-Lingual Hearing Impairment: it is deafness or hard of hearing which occurs before language skills have been acquired.
2- Post-Lingual Hearing Impairment: it is deafness or hard of hearing which occurs after language skills have been acquired.
What Are Hearing Assistive Technologies?
Hearing assistive technologies are devices that amplify, augment, or replace the need for sound in order to improve the day-to-day lives of people with hearing disabilities. The indispensable value of these devices in terms of allowing people to function fully and comfortably is recognized by the federal government. The Technology Related Assistance to Individuals with Disabilities Act of 1988 provides grants to U.S. states and territories in order to fund assistive technology initiatives.
Furthermore, the Americans with Disabilities Act not only requires that appropriate services be offered for people with disabilities in the public sphere, but also enforces requirements regarding “accessible design.” In a 2010 revision of the ADA, the latter feature was updated to stipulate that audio enhancement technology used for the public assistance of people with hearing disabilities must be updated and renovated to allow people with hearing aids or cochlear devices to use them without removing their personal devices. This is a large scale infrastructural change in the United States; and as such, this update only requires that at least 25% of publicly available audio augmentation receive these updates within the allotted time frame.
This appears to imply that further long-term updates will be regularly enacted. Much of these updates will involve the installation of hearing loops, which have long been a required hearing assistive technology in public spaces in the U.K. Hearing loops transmit sound directly to a hearing device using a magnetic field. This not only eliminates the need to remove hearing aids and cochlear implants for use, but works along with them in order to amplify the target sound to the exclusion of background noise.
Other legislation updating accessibility regulations, such as the 21st Century Communications and Video Accessibility Act (CVAA), have also been implemented to reflect the improved scope of modern assistive technology.
What Types of Assistive Devices Are Available for people with Hearing Impairment?
Assistive technologies vary greatly based upon the needs of the individual, and as such, hearing assistive technologies can be high-tech or low-tech, ranging from infrared audio transmission to vibrating alarm clocks. There are several different categories of hearing assistive devices:
Assistive Listening Devices (ALDs)
Augmentative & Alternative Communication (AAC) Devices
Alerting Devices
Hearing Aids
(1) Assistive Listening Devices (ALDs)
Assistive listening devices augment or amplify sound for people with partial hearing loss. Examples of an ALD would be hearing loops and FM systems.
Assisted Listening Systems and Devices
As stated, ALDs can vary greatly depending on the needs of the user. For example, one may be used to listen to a specific source of sound in large, loud areas, while another may be used to amplify a one-on-one conversation. The following list will detail many popular assistive listening devices and their uses.
Telecoil
A telecoil is a hearing aid attachment that converts magnetic signals into sounds. Users can turn the telecoil on or off as they please. Telecoils can be used in any space where a complementary loop system is installed. Spaces that utilize hearing loops may include everything from universities to airports.
FM Systems
FM systems are devices that utilize radio signals to transmit amplified sounds to a compatible receiver on the user’s person. These systems are useful when the listener is trying to focus on a single sound to the exclusion of others, such as in a classroom or theater.
Infrared Systems
Infrared systems convert infrared light into sound. Similar to other assisted listening devices, infrared systems require complementary output and input features—a device to produce the infrared light, and a device to receive and decode the infrared light. These can be used anywhere that the appropriate transmitters are installed. This may include anything from an auditorium to a theater.
Personal Amplified Systems
Personal amplification devices universally amplify sound input. They are often similar to hearing aids, but are less sophisticated technology. They are usually used by people with mild hearing loss.
Audio Induction Loop
Audio induction loops, or hearing loops, consist of three basic parts: a microphone, an amplifier, and a loop cable. This technology works in conjunction with telecoils. Similar to many other assistive listening devices, the essential premise of this device is the transmission of sound between the input device and the output device, in this case in the form of an electromagnetic field produced by the loop, which is installed along the perimeter of a room or building.
Amplified Telephones
Amplified phones allow users to adjust volume according to their needs. These phones also commonly offer features such as amplified ringers, telecoil compatibility, and portable amplifiers. These devices would normally be used by people who have mild to moderate hearing loss, as they are not of great help to people with complete or profound hearing loss.
Coupling Accessories
A “coupling accessory” is any assistive listening device that provides a connection between hearing aids or cochlear implants to another device, such as a phone, tablet, computer, smart home device, or wearable tech. These usually take the form of plug-ins or transmission technology, such as Bluetooth.
(2) Augmentative and Alternative Communication (AAC) devices
Augmentative and alternative communication devices replace verbal communication for people with full or profound hearing loss. Examples of an AAC would be captioning options and graphic organizers.
Augmentative and alternative communication (AAC) devices are devices that replace speech and audio queues with other forms of communication. These are especially helpful for people who have complete or profound hearing loss, as they do not benefit much, if at all, from assisted listening devices. AAC devices may range from picture boards to eye-tracking devices to speech-to-text software.
a. Telecommunication Devices
Telecommunication devices are devices that transmit information over a substantial distance, such as telephones, televisions, and computers. Such devices are becoming more and more prevalent in day-to-day life, and therefore assistive technology that augments these devices is essential for people with hearing disabilities. Many of these accessibility augmentations have to do with smartphones.
However, while accessibility options for smartphones are increasing all the time, both as part of their default settings and as apps, the specific options will depend on factors such as the specific phone or phone provider. For example, Android and Apple phones will not always offer the same apps, and a larger wireless provider will often have more resources at their disposal than a smaller provider.
Video-phones With Screen
While a “videophone” may sound like a description of a standard smartphone, video phones are a telecommunication device specifically developed for people with hearing disabilities. The display is often larger than one would find with a smartphone, and they are designed to be comfortably used hands-free, in order to allow the user to use sign language.
In some capacities, the uses of a videophone are very similar to live video communication options you would find on many standard smartphones. This allows two people to use sign language to communicate with each other.
However, video phones also often utilize third-party services that enable a person who has a hearing disability to communicate with someone who does not through an interpreter. The user will communicate with the interpreter through video, and the interpreter will then translate what the videophone user is saying to the other person. In the first scenario, both parties need a videophone, while in the second, the party with a hearing disability is the only one that needs to use a videophone.
Voice Carry Over Telephone
A voice carry over (VCO) telephone allows people with hearing disabilities to speak to another party, and then receive the response in text format. The response from the other person is transcribed by a third-party. This is not the same as a hearing carry over telephone, which fulfills the opposite function for people with speech disabilities.
Caption Telephone
A caption telephone (CapTel) is a phone with a screen that displays captions. Like many similar services, this involves the use of a third party. The third-party reiterates what one speaker is saying into speech-to-text recognition software, and the transcription is then sent to the person with the CapTel.
TTY/TTD/TT/RTT
TeleTYpe (TTY), Telecommunications Device for the Deaf (TDD), and Text Telephone (TT) are interchangeable terms that all refer to a system that allows text-to-speech communication through a third-party. A person with a hearing disability types what they would like to say, a third party reads the communication, and then the third party verbally conveys the information to the person on the other line. The third party then transcribes what the second person says, and sends the text version of the communication to the first person. Text telephone input devices are usually a standard-size keyboard.
Meanwhile, RTT (Real-Time Text) is very similar, but it is more straightforward. There is no third-party, and the conversation is held completely in writing. This may sound like standard texting, but, as the name implies, RTT is real-time. Rather than completing a message, sending it, then waiting for a response, RTT allows each user to see what the other is typing as they are typing it. In this way, it more accurately replicates a face-to-face conversation in terms of reaction time.
b. Communication Access Realtime Translation
Communication Access Realtime Translation (CART) is a speech-to-text system, also known as “real-time captioning.” This is a computer-translation system which captions audio as it occurs, rather than being pre-transcribed. In addition to the obvious benefits for people with hearing disabilities, CART can supplement assistive listening devices by providing redundancy in the user’s input. If they miss something through one channel, they can receive clarification through the other. CART may be performed on location or remotely by specially-trained providers.
Closed Captioning
“Closed” captioning refers to captions that are on a separate track from the main video, and therefore can be turned on and off. Closed captions are more common than open captions, and are usually used in scenarios where an individual has the option to choose whether they want captions or not, such as in the case of watching television in your own home.
Open Captioning
“Open” captioning refers to captions that are part of the actual video, and therefore cannot be turned off. These may be used whenever a video is being presented to a large group, where one user’s preference is not the priority. This may happen in a movie theater or at a conference.
(3) Alerting Devices
Alerting devices are technology which replaces the need for audio signaling. These include things such as vibrating alarm clocks and apps which alert the user to a ringing doorbell.
Whereas ALDs and AAC devices amplify or provide an alternative means of communication, alerting devices alert the user to important audio stimuli in their environment. These audio stimuli include things such as alarms, doorbells, barking, or important news alerts. Many of these alerts are available as smartphone apps. The alerting device may employ many methods to get the user’s attention, including an especially loud noise, a tactile sensation, or a flashing light. The following are a few common examples of alerting devices:
Smoke Alarms and Carbon Monoxide Detectors
Smoke alarms and carbon monoxide detectors are life-saving devices, and as such, it is vital that people who cannot hear the normal alarm sound can still be alerted to the possible danger. A common smoke alarm/carbon monoxide alert system for people with hearing disabilities is a bright strobe light attached to the alarm.
Doorbell Signalers
Doorbell signalers alert people with hearing disabilities to the ringing of their doorbell. There are many types of doorbell signalers; some are actually installed as part of the doorbell system, and some operate separately. Bright strobe lights and phone apps that cause your phone to vibrate are some commonly used doorbell signalers.
Telephone Signalers
Telephone signalers alert people who are deaf or hard of hearing when their phone is ringing. To some degree, common phone settings such as vibration alerts can be used to assist people with hearing disabilities. However, other signaling options, such as flashing lights, are also available.
Wake Up Alarms
Alert devices can also help wake up people with hearing disabilities at their desired time. Bed shakers or other vibrating devices are the most common alarm clock alternatives for people with hearing disabilities.
Baby Signalers
Baby signalers alert parents or caregivers when the baby is crying. In fact, some devices go so far as to assess the baby’s needs based on the sounds of the cry, e.g. whether they are hungry or distressed. These alert systems run the gamut in terms of what type of alert they use, depending on the device. For example, some may utilize mattress or wearable vibration mechanisms, while others may employ flashing lights. A video feed is also a great option for parents who are deaf or hard of hearing.
Weather Alerts
Emergency weather alerts are an important safety precaution for anyone, so it is important that people who are deaf or hard of hearing are also immediately alerted about the situation. These alerts also often take the form of flashing lights or vibrations.
Other Alerting Devices
(4) Hearing Aids
These are the most commonly used ATs that amplify sound to enable hearing easily. They are used by children and adults with hearing disabilities.
Eye glass hearing aids: in this type of hearing aids, the aid is glued into the frame of the pair of the eye glasses. When the eye glass is worne, the aid rests on the ear and amplifies sound to the hearing of the Individual.
Behind the ear hearing aids: this type of hearing aid is designed to be placed behind the ear.
In the ear hearing aids: this type of hearing aid is designed to be inserted or fixed in the ear canal.
Apps for the Deaf and Hard of Hearing
There are countless apps available to assist people with hearing disabilities. The following is a small selection of popular apps:
Ava: This is a speech-to-text app with a group text option.
Baby Sign and Learn: This app teaches babies and toddlers sign language using age-appropriate videos and flashcards.
Live Transcribe: This app is built on Google’s own proprietary speech recognition technology. It transcribes audio into text, and provides the user with various input and display options.
Mimi Music: This app assesses the listener’s hearing abilities and then uses the information to adjust the music to be more clear at a safe volume level.
Sound Alert: This app allows you to record your desired sound alerts, such as doorbells or oven timers, and then choose your preferred alert signal. When the phone later detects this sound, it will signal the user.
Sound Print: This app documents the noise levels of different areas in order to allow people with hearing disabilities to find quieter public areas.
Tunity: This app identifies television channels using the device’s camera, and then allows the user to stream the audio from the television straight to the device.
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