Understanding Hearing Impairment written by Michelle Tjelmeland
What is hearing impairment and why is early invention so important?
The term hearing impairment encompasses a continuum of hearing loss from slight to profound. “The Hearing Impaired Manual: Recommended Procedures and Practices” explains the term hearing impairment,“The child’s residual hearing is not sufficient to enable him or her to understand the spoken word and develop language, thus causing extreme deprivation in learning and communication. Or the child exhibits a hearing loss which prevents full awareness of environmental sounds and spoken language, limiting normal language acquisition and learning achievement” (5).
Once a hearing loss has been confirmed by medical experts parents will then be able to choose appropriate assistive technology to facilitate their child’s hearing loss. Furthermore, parents will then be able to help their child develop the necessary skills needed to acquire speech and language skills and communicate effectively. Early detection of a hearing loss is imperative so invention and treatment can be established immediately. Untreated hearing loss will inevitably cause a child to be severely delayed with thinking skills and speech and language production. When a child is unable to clearly hear phonetic distinctions during the first year of life, the child is at substantial risk for language learning problems. Consequently, the child will suffer delays or failure within the educational environment and amongst peers (Schwartz, 2). Parents of a child with hearing impairment must be well-informed about their child’s hearing disability. Obtaining treatment and diagnosis of a child’s hearing loss as early as possible is imperative so intervention and a individualized management plan can be established.
How does the ear work?
One must understand how the ear works in order to understand the type of loss their child has. To explain, “sound travels through the air in the form of waves of varying frequency. The frequencies of these waves determine the pitches of the sound that is heard. Sound waves are channeled into the external ear canal where they are transmitted to the middle ear which consists of the eardrum and three small bones in the ear cavity. This part of the ear serves as an amplification system. The middle ear compensates for the loss of the intensity of sound as it travels from the air medium of the middle war to a fluid medium within the inner ear known as the cochlea. Sound travels as waves of fluid to a specific area depending on the frequency of the sound in the cochlea. The fluid movement then causes the tectorial membrane to vibrate against the hair cells which then stimulates the auditory nerve. The auditory nerve is responsible for transmitting the sound stimuli to the auditory center in the brain. The components that make up the sound and speech that are heard are coordinated and sent to higher centers of the brain for interpretation “
( Schwartz, 3).
Below is a diagram of the ear:
- Helix - The in-curve rim of the external ear
- Antihelix - A landmark of the outer ear
- Lobule - A landmark of the outer ear. The very bottom part of the outer ear
- Crest of Helix - A landmark of the outer ear
- ExternalAuditory Meatus - or External Auditory Canal. The auditory canal is the channel through which the sounds are led from the ear outside to the middle ear.
- Eardrum - (tympanic membrane) A thin layer of skin at the end of the external ear canal
- Auditory Ossicles - The three small bones in the middle ear, know as the hammer (malleus), anvil (incus) and stirrup (stapes) which are connected to one another. Together these ossicles are called the ossicular chain. Their purpose is to lead the sound striking the eardrum further into the inner ear
- Oval Window - An opening in the bone between the air filled middle ear cavity and the fluid filled inner ear, and is covered by a thin membrane
- Cochlea - Part of the inner ear that contains part of the hearing organs.
- Semicircular Canals - Part of the organ of balance that is part of the inner ear
- Eighth Nerve - Nerve that transmits messages from the inner ear to the brain.
- Eustachian Tube - A tube connecting the middle ear cavity and the pharynx (back of the throat). It can be opened by coughing or swallowing, though it is normally closed. The occasional opening of the Eustachian tube is necessary to equalize are in the middle ear cavity.
Can your child hear? Checklist and Milestones.
Hearing impairment is often referred to as the invisible handicap. According to the “Choices in Deafness” book, nearly “4,000 babies are born profoundly deaf every year in the United States. Another 10-15 percent of newborns demonstrate partial hearing loss that is educationally significant”(1-2).
Because a hearing loss is not visible, it is often overlooked and can go undetected for some time. Surprisingly, an educationally significant hearing loss may go undetected in a child as late as six years of age, even with the most advance medical techniques available(Schwartz,2). Below is a checklist of milestones from the Bill Wilkerson Center that your child should be accomplishing at various ages:
|3 to 6 months
||Enjoys rattles and other sound making toys
Responds to pleasant tones by cooing
Stops playing and appears to listen to sounds or speech
Watches a speaker’s face
Begins to turn head toward sounds that are out of sight
|Laughs out loud
Cries differently for pain,hunger, and discomfort
Coos-produces an assortment of oohs, ahs, and other vowel sounds
|6 to 9 months
||Responds to soft levels of speech and other sounds
Temporarily stops action in response to “no”
Turns head directly toward voices and interesting sounds
Begins to understand routine words when used with a hand gesture( e.g. bye-bye or up)
|Babbles-repeats consonants-vowel combinations such as ba-ba-ba
Makes a raspberry sound
Makes sounds with rising and falling pitches
|9 to 12 months
||Follows simple directions presented with gestures (e.g. give it to me, come here)
Responds to his or her own even when spoken quietly
Will turn and find sound in any direction
|Vocalizes to get attention
Produces a variety of speech sounds (e,g,m,b,d) in several pitches
|12 to 18 months
||Knows the names of familiar objects, persons, pets
Follows routine directions presented without gestural or visual cues (e.g. come here, clap hands)
Identifies sounds coming from another room or outside
Enjoys music and may try to dance
|Uses 2 to 3 words spontaneously
Imitates simple words
Uses jargon speech (babbling sounds like real speech to communicate)
Points to request or draw attention to objects, people and events
|18 to 24 months
||Points to two or more body parts
Identifies five or more pictures of common objects when named
|Uses vocabulary of 20 + words
Uses jargon speech with intelligible words
Says “no” or “no-no” in response to questions and commands
|24 to 30 months
||Responds to two-part command(e.g. get the shoe and bring it to me)
Listens to simple stories understands possessive terms (my, mine, yours)
|Puts together two or more words to make simple sentences
Uses a vocabulary of 50 + words
50% of speech can be understood by unfamiliar listeners
|30 to 36 months
||Answers “what” and “who” questions
Identifies objects and pictures by use(e.g. show me what you sit on)
Easily follows simple conversation
Understands basic concepts
|Consistently uses 2 to 3 word sentences
Ask “what” and “where” questions
Uses some plural(e.g. cars) and verb markers e.g.running)
50-75% of speech can be understood by unfamiliar listeners
If your child fails any two items in the age appropriate category you should call your doctor and express your concerns.
Risk factors and indicators that place an infant at risk for hearing impairment.
There are several indicators that may help parents determine if their child has a hearing loss. One of more of the following factors taken from “Choices in deafness”, A Parents’ Guide to Communication Options, may indicate your child has a hearing loss:
- Family history of hearing loss
- History of material illness or maternal ototoxic drugs
- Birth weight under 3.3 pounds
- Presence of other head, facial, external ear abnormalities
- Prolonged neonatal jaundice
- Poor APGAR rating
- Admission to newborn intensive care unit
- Parental or caregiver concern about hearing and speech development
Additional signs or indicators of hearing loss in older children are ringing in the ears, saying “what” frequently, reading lips or watching the faces of speakers intently, listening to the radio or TV loudly, inconsistent or little or no response to voices or other sounds (National, 80). Remember to refer often to the hearing milestone checklist to ensure your child is meeting the appropriate receptive and expressive goals for his or her age.
It is extremely important to note that only 50% of children with a hearing loss have any indicators. Therefore, if parents suspect that their child cannot hear or think their child does not respond appropriately it is imperative to talk with doctors, preferably an Ears, Nose, and Throat Specialist (ENT) and voice their concerns.
Typically, the doctor will request the parents fill out a family history questionnaire. Once the family history information has been completed, the doctor will complete a physical examination of the child and the child’s ears. Next, the doctor will order a complete audiological assessment to determine if your child suffers from a hearing loss.
Pediatric hearing assessment procedures.
Children who may have a hearing loss are tested both objectively and subjectively. Objective tests seem to be the most reliable since they do not require responses from the child. Impedance and Otoacoustic Emissions Testing are the two most frequently performed objective tests. These tests evaluate the function of the ear. Impedance testing is essential for determining if a child’s middle ear is functioning properly. In order to determine if the cochlea or inner ear is functioning properly an Otoacoustic Emissions Test is helpful. An auditory brainstem response (ABR) test is yet another objective test. This ABR tests the electrical activity of the brain (Schwartz, 18).
The most common impedance test given is a tympanometry test. A tympanometry test measures how well the middle ear is functioning, how well the sound reaches the middle ear, and how flexible the middle ear is. This is a painless test taking only a few minutes to perform. A small molding similar to a hearing aid mold is placed inside the child’s ear. Again, this test measures how well the sound reaches the inner ear or cochlea. If fluid is present in the child’s ear the test will indicate this abnormality. It is important to note that a tympanogram can be normal but the child can still have a hearing loss.
An Electrophysiological test known as the auditory brainstem response(ABR) test is yet another objective test performed to determine hearing loss. The ABR tests the electrical activity of the brain. This test can sometimes be more helpful in determining hearing loss in infants because it does not require the child to respond to sounds or tones. Often times an audiologist may want to perform an ABR if she feels that the behavioral test was not accurate.
The ABR is not a painful test. However, it is usually recommended that a child be sedated when this test is performed in order to get the most accurate results. After the child is asleep electrodes connected to a computer are placed behind the ears and on the forehead. Sometimes headphones may be placed on the child. Sounds, tones, or clicks are sent through the wires or headphones. The computer will then measures the brain’s activity as the sounds are conducted through the electrodes.
Behavioral testing may also be helpful in determining hearing loss in a child. Unlike the tympanometry test and ABR, the behavioral tests require the child to respond to sound in some way. Because behavioral testing is considered subjective, it is not always reliable. Behavioral testing is conducted in a sound proof room where sounds like clicks, tones, noises, and speech are presented through speakers, headphones, or a bone vibrator. Behavioral testing helps one learn how a child hears sound. There are four types of behavioral tests performed: pure-tone air conduction, pure-tone bone conduction testing, speech reception threshold testing, and word recognition testing. In pure tone testing, tones are sent to the child through headphones, where as with pure tone bone conduction, testing tones are presented through a vibrator. Pure tone screening is typically the type of test used in schools to screen children. Speech audiometry testing, which includes speech reception threshold and word recognition testing, evaluates the child’s ability to hear and understand speech through a presentation of words at a variety of loudness levels. Several factors will determine what type of behavioral test a child will be given. The sounds and tests that will be used depend on the age of the child, the age at which the loss occurred, and how long the child has had a hearing loss ( Schwartz, 20).
Once the hearing loss has been determined through proper audiological assessment, one can then explore various amplification alternatives.
The most common types of hearing loss.
There are three types of hearing loss: conductive, sensorineural, and mixed. A conductive hearing loss is a result of damage to outer or middle ear. Conductive losses are not severe and often times can be surgically corrected. A person with a conductive loss may reap great benefits from hearing aids. A sensorineural hearing loss is a result of damage to the hair cells of the inner ear or nerves. This type of loss ranges from mild to profound and is permanent. In other words, surgery cannot be performed to correct a sensorineural hearing loss. Often times, hearing aids are not helpful either. While the aids may amplify sounds, the sounds are still distorted. A mixed hearing loss simply means that the hearing problem occurs in the outer or middle ear and inner ear.
Degrees of hearing loss.
There are different degrees of hearing loss. Below is a chart which lists and classifies the degrees of hearing loss according the dB range in which sound is heard. Please refer to audiogram below.
|Degree of hearing loss
|Mild Hearing Loss
||26-40 dB (Purple)
|Moderate Hearing Loss
|Moderately Severe Hearing Loss
|Severe Hearing Loss
|Profound Hearing Loss
||Over 90 dB (Blue)
What is an audiogram?
Once a child is tested, the results of the hearing test will be charted on an audiogram. The audiogram indicates how softly a tone can be heard. The audiogram classifies the type of hearing loss, the degree of hearing loss, the configuration of hearing loss, and symmetry of hearing loss.
Below is an example of an audiogram:
The numbers across the top of the audiogram represent tone frequencies. As the numbers become larger, the pitch of the tones becomes higher. The numbers on the left hand side of the audiogram indicate the loudness of sound. The loudness of sound is known as decibel (dB). The higher the dB, the louder the sound.
Audiogram configurations of hearing loss.
Next, one must understand the configuration of a hearing loss. There are three types of configurations: rising, sloping, and flat. A rising configuration means that a person can hear high pitch tones better than low pitch tones. A sloping configuration means that a person can hear low pitch tones better than high pitch tones. Finally, a flat configuration means that a person needs the same amount of loudness to hear a low or high pitched sound (Schwartz, 31).
Below are examples of audiogram configurations:
Finally, it is important to understand the symmetry of a hearing loss. If a person has the same degree and type of hearing loss and configuration in each ear, the loss is symmetrical. However, if the degree and type of hearing loss and configuration varies or is different in each ear, the loss is classified as asymmetrical.
Once the hearing loss has been determined through proper audiological assessment, one must then explore various amplification alternatives.
Hopefully, this information is helpful to parents who are trying to determine if their child is hearing impaired. Obviously, it is important to understand the appropriate steps to take in determining a hearing loss. One you have acquired the basic knowledge regarding hearing loss, you can begin to explore the various options available to help your child.
National Information Center on Deafness (NICD) (1991). Growing Together:Information for Parents of Deaf and Hard of Hearing Children. Washington, D.C.: NICD.
Schwatz, Sue (Ed.) (1987). Choices in Deafness: A Parents Guide. Kenington, MD: Woodbine House.