[Layout Image: No Content]
Gallaudet Univeristy
Decorative Graphic: No content.

Understanding Hearing Ability

This information is part of an online guide, Resources for Mainstream Programs

What does speech sound like to deaf and hard of hearing children? Do deaf children hear anything?

Some deaf children do in fact have no measurable hearing, but most children have some degree of residual or remaining hearing. Every child is unique in the sounds he or she can hear and his or her ability to understand them. No two children are alike. Two children who perform similarly on their hearing tests may understand or use sounds in very different ways. It is important never to assume how a student should or will communicate because of hearing test results.

Whether a student can use his or her hearing to understand speech or recognize sounds in the environment is influenced by many factors, including:

  • Age of hearing loss onset. The situation of a child who has heard spoken language prior to the loss of hearing is different from that of a child who was born deaf or who became deaf prior to developing spoken language. The child who becomes deaf after spoken language is established is already familiar with the spoken language of the home. With appropriate hearing aids or a cochlear implant, these children are more likely to be able to maintain their spoken language abilities. Children who are born deaf and have never heard spoken language have varied outcomes in the development of spoken language based on how much benefit they get from a hearing aid or a cochlear implant, and a range of other factors.
  • Age at which hearing loss is diagnosed and communication and educational support are initiated. Early identification of hearing loss, coupled with appropriate educational supports to promote the development of early language and communication (in sign language, spoken language, or both), will minimize delays in all areas of development.
  • Degree, type, and pattern of hearing loss. There is no single description or profile of "deaf" or "hard of hearing" that fits all children. Even if two children have the same degree, type, and pattern of hearing loss, it does not mean they will hear and understand in the same way.
  • Educational and communication choices that families make for their children.
  • Consistency with which the student uses assistive listening devices (hearing aid, cochlear implant, FM system).
  • The extent to which the family is involved in developing the child's spoken language and speech skills.  

Characteristics of Hearing Loss

The characteristics of hearing loss include:

  1. the degree (severity) of hearing loss,
  2. the configuration (pattern) of the hearing loss on the audiogram, and
  3. the type of hearing loss (where the hearing loss occurs in the auditory system).

Each degree, type, and configuration of hearing loss can impact the development of language, speech, and communication and the student's educational placement.

1. Degree of Hearing Loss

Hearing loss is typically described in decibels. For example, you may learn that a student has a 75 dB hearing loss. This usually refers to the student's pure tone average (average of thresholds to tones documented on the audiogram at the pitches/frequencies 500 Hz;1,000 Hz; and 2,000 Hz). It is not acceptable terminology to describe hearing loss in percentages. For example, references to a 75 percent hearing loss have no audiological meaning. The varied degrees of hearing loss based on an individual's pure tone average are as follows:

  • Normal range 0-15 dB HL
  • Minimal 16-25 dB HL
  • Mild loss 26-40 dB HL
  • Moderate loss 41-55 dB HL
  • Moderately severe 56-70 dB HL
  • Severe 71-90 dB HL
  • Profound 91 dB HL or greater

3. Types of Hearing Loss

The four common types of hearing loss are: sensorineural, conductive, mixed, and unilateral. Another less common type of hearing loss is auditory neuropathy. Each type of hearing loss is described below, alone with student profiles to  help you understand how the type, degree, and pattern can influence the child's development of language and speech development. Educational considerations also are included.

Sensorineural Hearing Loss

Sensorineural hearing loss is caused by damage to the hair cells in the cochlea of the inner ear. Sensorineural hearing loss is permanent and cannot be reduced or eliminated by medication or surgery. There are many different causes of sensorineural hearing loss, some developing before or during birth and others having a later onset.

Onset before or during birth:

  • Maternal infections such as rubella, herpes, toxoplasmosis, syphilis, cytomegalovirus (CMV)
  • Heredity (genetics)
  • Asphyxia or lack of oxygen at birth
  • Possible association with birth weight of less than 1,500 grams
  • Possible association with defects of the head and neck
  • Possible association with maternal drug or alcohol abuse

Later onset (can occur any time after birth):

  • Bacterial meningitis
  • Ototoxicity (drug induced)
  • Intense or excessive noise
  • Physical trauma to the head or ear
  • Aging (the most common cause in older adults)

The following characteristics are typical of sensorineural hearing loss:

Students with a sensorineural hearing loss may experience both distortion and decreased loudness of sounds. This occurs because some or all of the hair cells in the inner ear responsible for sensing sounds of different pitches are damaged or nonexistent or because the auditory nerve (the pathway for sound to travel to the brain) is damaged or nonexistent. The extent of damage to the hair cells in the cochlea and the auditory nerve will cause varying degrees and patterns of hearing loss.

Students with a sensorineural hearing loss may experience varying levels of benefit from assistive listening devices. For example, some children benefit from a hearing aid to understand spoken language, while others find hearing aids beneficial only for awareness of environmental sounds.

Case Study: Sarah, age 5
Background:

  • Sarah has profound sensorineural hearing loss identified at birth. She is aware only of low frequency sounds.
  • Family learned and introduced ASL to Sarah immediately following diagnosis. Sarah has age-appropriate ASL development.
  • Sarah has used a hearing aid since age 6 months; she is aware of some environmental sounds and understands some spoken words when she can see the speaker's lips and face.

Considerations for the school program:

  • Use of an ASL interpreter in the classroom and for social activities so Sarah can fully participate in all activities.
  • Annual language evaluation in both ASL and English to confirm that Sarah's language levels remain age-appropriate.
  • Provision of auditory and speech habilitation services by a speech-language pathologist to work on skills related to the development of spoken language.
  • Annual audiological evaluation and hearing aid check by a pediatric audiologist.

Case Study: Matthew, age 4
Background:

  • Matthew has severe to profound sensorineural hearing loss identified at birth. He is aware of both low and high frequency sounds.
  • Binaural hearing aids were fitted at 3 months. Family uses only spoken English.
  • By age 18 months, Matthew was developing spoken words and seemed to get some benefit from his hearing aids but was still struggling to understand increasingly complex language.
  • Family decided to obtain a cochlear implant; cochlear implant surgery was completed at age 2.
  • Matthew is doing well with his implant; however, he continues to exhibit a one-year delay in spoken language in relation to his hearing peers.

Considerations for the school program:

  • Do a quick check of the cochlear implant daily to make sure it is working.
  • Refer Matthew for mapping (adjusting) of cochlear implant approximately every 6 months through the hospital cochlear implant center.
  • Monitor Matthew's understanding of new information. He understands spoken language socially and when the language is familiar, but he has difficulty in academic situations when the language is complex and new information is presented.
  • Matthew has difficulty listening in the presence of background noise. An FM system should be used along with his cochlear implant.
  • Provide auditory and speech therapy to continue to work on developing spoken language skills with his cochlear implant.
  • Conduct annual speech and educational assessments to ensure Matthew continues to progress academically and to address any ongoing spoken language delays.

Case Study: Charlene, age 9
Background:

  • Charlene has moderate sensorineural hearing loss.
  • Hearing and speech milestones were developing normally until age 3.5 years when a change in auditory behavior suggested the presence of a progressive hearing loss.
  • Hearing aids were fitted immediately after the hearing loss was diagnosed.
  • Charlene's hearing has remained stable for five years.
  • With hearing aids and an FM system, Charlene was able to recover lost spoken language growth and is currently age appropriate in her spoken language development in comparison with her hearing peers.
  • Appears to be functioning with minimal difficulties in her mainstream classroom.

Considerations for the school program:

  • Should be given accommodations in classroom seating so that she can easily see the teacher.
  • Use an FM system to limit impact of noise on listening for classroom information.
  • Establish communication guidelines in the classroom to facilitate access to group discussions (i.e., students to raise their hands and teacher to identify the speaker before discussion proceeds).
  • Monitor stability of hearing levels and appropriateness of hearing aid and FM system fitting with annual audiological evaluation.

Conductive Hearing Loss

Conductive hearing loss is caused by a problem in the outer or middle ear. Sound is ineffectively "conducted" to the hair cells in the inner ear that are responsible for sensing sound. In a purely conductive hearing loss, the actual hair cells/nerves of hearing are intact and ready to accept incoming sounds. Sound, however, does not adequately reach these hair cells/nerves. Sounds therefore are heard at a reduced level. The degree of loss depends on what is causing the problematic sound conduction.

The following characteristics are associated with conductive loss:

  • The hearing loss can usually be reduced or eliminated through medical treatment.
  • The condition may be temporary, depending on the nature of the blockage.
  • If the hearing loss is brief (less than two or three weeks and not frequently recurring), it should not affect language or academic development. If the blockage is chronic or repeated, it may influence speech, language, and educational performance.
  • Students who speak loudly, pull on their ears, frequently ask for repetition, or say, "Huh?" may be showing symptoms associated with a conductive hearing loss. A referral to the school nurse, speech-language pathologist, or audiologist may be appropriate even for a student who does not regularly receive special education services.

Use of a hearing aid or other assistive listening device may help overcome a long-term conductive hearing loss so the student does not experience problems in language development and education. A surgically implanted device called the Baha system is designed to overcome amplification obstacles of traditional hearing aids for permanent conductive hearing loss. Similar to a cochlear implant, but avoiding the cochlea and inner ear entirely, the Baha system combines a sound processor with a small titanium implant behind the ear. The system allows sound to be conducted through the bone rather than the ear. Surgery is minor, and many patients report a wide range of advantages over other hearing devices. (See http://cochlearamericas.com.)

Routine monitoring of hearing is recommended (ask the audiologist to determine how often) for children who have repeated conductive or middle ear problems. Children with ear infections or other middle ear problems who demonstrate ongoing behavioral problems or appear to not pay attention may have fluctuating conductive hearing loss.

Case Study: Christopher, age 6
Background:

  • Christopher has experienced middle ear fluid with infection since birth.
  • Infections were treated with antibiotics during early childhood, however fluid often lingered after the infection was clear.
  • During times when Christopher was experiencing fluid, hearing tests showed he had a mild to moderate conductive hearing loss in both ears.
  • By age 3, speech and language milestones were delayed approximately one year, and pressure equalizing (PE) tubes were inserted.
  • After one year, the PE tubes fell out. Since that time, Christopher continues to experience repeated ear infections and the family is considering inserting new PE tubes
  • Language evaluation continues to demonstrate a one-year delay in language development.

Considerations for the school program:

  • Monitor for behavior that indicates that Christopher may have fluid in his ears (i.e., irritable, not paying attention, saying, "Huh?").
  • Provide flexible seating and make necessary accommodations (i.e., moving closer to Christopher) to assure he does not miss important information.
  • Review language evaluations to understand and assist Christopher in addressing language gaps that resulted from his ongoing previous conductive hearing loss episodes.
  • Repeat language evaluations annually to assure that language gaps are not growing and de-termine if intervention provided by a speech-language pathologist is necessary.

Ear Infections, Fluid, and Hearing Loss

Many children experience episodes when fluid becomes trapped behind the eardrum in the space of the middle ear. When fluid is present in the middle ear, children suffer a temporary hearing loss since sound is not conducted adequately to the inner ear. This fluid may be thin or thick and may or may not be infected. If middle ear fluid/infection is suspected, the family should consult with the child's physician to determine necessary medical or audiological follow-up. If infected, treatment may include the use of antibiotics. Antibiotics may alleviate the infection, but fluid may remain in the middle ear for several days or weeks. If fluid becomes chronic and is not remedied with medication protocols, the surgical insertion of small tubes (PE tubes) in the eardrum to promote drainage of the fluid is sometimes recommended. For children with normal hearing, fluid in the middle ear places a strain on the hearing system. Even if not permanent, fluid in the middle ear, if repeated or chronic, can have a negative impact on the development of a child's language and education. For more information on ear infections, see http://www.nidcd.nih.gov/health/hearing/otitism.htm#what.

Mixed Hearing Loss

A child with mixed hearing loss will have a combination of characteristics associated with both conductive and sensorineural loss. The extent of the conductive and sensorineural components will determine the implications of the mixed loss.

In a mixed loss, the conductive component may be permanent or temporary. For example, the conductive component of a mixed loss may be permanent when there is damage to the ossicles (middle ear bones) or there is some anatomical malformation that blocks sound from reaching the inner ear. Usually, the conductive component in a mixed loss is temporary due to fluid or excess wax. Thus, the conductive component of the hearing loss resolves with medical attention, leaving only the permanent, sensorineural component of hearing loss. When the conductive component is temporary, hearing levels will fluctuate depending on whether the conductive component is present. Some characteristics associated with mixed hearing loss include the following:

  • When hearing levels fluctuate, it can impact day-to-day listening and attending. Hearing aids may need to be adjusted or have multiple settings for times when hearing levels fluctuate.
  • If the conductive component is significant, but there is very minimal sensorineural hearing loss, the student most likely will hear sounds softly but with little distortion.
  • If the sensorineural component is more significant, and the conductive component is minimal, the sounds the student will hear will be distorted in addition to softer.
  • Depending on the reason for the conductive component of the hearing loss, mixed losses may fluctuate and the child's listening experiences could vary from day to day.

Case Study: Melissa, age 4
Background:

  • Melissa has had a moderate sensorineural hearing loss since birth.
  • Melissa also has recurrent ear infections with fluid. She can participate effectively in the classroom when she has on her hearing aids and she is not experiencing ear fluid. However, when she has fluid, she is often unable to keep up with class discussions.
  • The family is considering obtaining PE tubes for Melissa.

Considerations for the school program:

  • Observe Melissa for possible symptoms associated with middle ear episodes/decreased hearing that may further impact her attending to classroom discussions.
  • Refer the family to Melissa's audiologist to change her hearing aid settings to compensate for the additional conductive hearing loss when she is experiencing middle ear fluid.
  • If Melissa obtains PE tubes, there may be times-while the fluid is draining through the tubes-when she cannot use her hearing aid(s). During these times, Melissa will need additional accommodations to succeed in the classroom.

Unilateral Hearing Loss

In unilateral hearing loss, hearing levels are normal in one ear and decreased in the other. This causes varying degrees of difficulty depending on how significant the hearing loss is in the single ear. Students with a mild hearing loss in one ear may or may not demonstrate linguistic, academic, or communicative delays. Students with a significant degree of hearing loss in one ear may experience language or learning delays and also have difficulty attending in the classroom. Students with a unilateral hearing loss are considered to be at higher risk for academic failure, classroom behavior problems, and linguistic delays compared to students with normal hearing.

People often assume that students should have no problem listening with their "good ear," but hearing with one ear is not the same as hearing with two ears. Students with a unilateral hearing loss may not hear all of the sounds in a classroom, and they may have a harder time locating the source of a sound. This is especially true when there is background noise or a great distance between a student and the person speaking. As a result, the student may miss important information. Special attention should be given to students with unilateral hearing loss who also experience intermittent or chronic middle ear problems. Any fluctuating or temporary conductive hearing loss in a student's "good ear" can further impact his or her listening and attending skills.

Children with a unilateral hearing loss may need special accommodations to support them in the classroom, including:

  • preferential seating for maximum accessibility to auditory information, • use of a sound-field FM system, and
  • ongoing monitoring for linguistic, educational, or social gaps.

For more information about unilateral hearing loss, see the Center for Disease Control (CDC) website: http://www.cdc.gov/ncbddd/ehdi/unilateralhi.htm.

Case Study: Charlie, age 10
Background:

  • Charlie's hearing is normal in the right ear. There is a profound hearing loss with no measurable hearing in the left ear. Charlie does not benefit from using a hearing aid in the left ear.
  • Language development is essentially within normal range. Academic levels are in the lower range for his class.
  • Charlie prefers not to participate in large group discussions.
  • Charlie sometimes gets in trouble for not paying attention.

Considerations for the school program:

  • Place Charlie's desk so that his right ear is closest to the teacher.
  • Make sure Charlie is not seated with his right ear (good ear) near an adjacent wall or window.
  • Consider obtaining a sound-field FM system that uses a small speaker placed close to the student.
  • Teach Charlie confirmation strategies such as repeating directions or asking for clarification of missed information so that he can ensure he has understood what someone has said.
  • Check in with Charlie privately to make sure he is following class discussions.

Auditory Neuropathy/Auditory Dyssychrony

Auditory neuropathy or, as some describe it, auditory dyssychrony (AN/AD), is a relatively new category of hearing loss. It is now identifiable due to improved diagnostic technologies available for audiological evaluation. AN/AD is a hearing disorder in which sound enters the inner ear normally, but the transmission of signals from the inner ear to the brain is impaired (See National Institute on Deafness and Other Communication Disorders, http://www.nidcd.nih.gov/health/hearing/neuropathy.asp).

Students with this disorder are often aware of sounds, but their ability to decode spoken language is hindered. That is, the students may "hear" sounds, but they may not necessarily make sense of them for communication.

There is still much to be learned about students with hearing loss characteristics consistent with AN/AD. Such students do not present themselves with a single profile. Just as there is a range of hearing levels with sensorineural hearing loss, there is also a range of levels with AN/AD.

AN/AD is sometimes confused with Auditory Processing Disorder (APD). Children with AN/AD and APD may demonstrate similar language processing difficulties. APD results from a dysfunction in the centers of the brain that process sound. AN/AD results from a dysfunction in the auditory system rather than the brain, thus making it a type of hearing loss. (See National Institute on Deafness and Other Communication Disorders, http://www.nidcd.nih.gov/health/voice/auditory.htm). Some students with AN/AD benefit from a hearing aid or personal FM system, while others do not. Some may be candidates for a cochlear implant. Others may benefit from sign language or Cued Speech. Educational professionals need to maintain a close working relationship with a child's doctors and audiologist in order to monitor a child's progress and treatment for AN/AD.

Case Study: Diana, age 5
Background:

  • Diana's newborn infant hearing screening was within normal range.
  • Spoken language milestones were delayed, and at age 18 months a hearing evaluation was finally completed.
  • A hearing evaluation, not administered until age 18 months, was consistent with a diagnosis of AN/AD.
  • Even with a hearing aid, Diana's spoken language did not develop and she was fitted for a cochlear implant at age 4.
  • Diana's spoken language development improved but continues to be delayed approximately 1.5 years.

Considerations for the school program:

  • Provide instruction within small groups within the classroom as often as possible.
  • Use resource room support.
  • Address language delays through speech-language pathologist services.
  • Maintain a spare supply of batteries and replacement parts for the cochlear implant at school.
  • Do a quick check of the cochlear implant daily to make sure it is working.
  • Refer Diana for mapping (adjusting) of the cochlear implant approximately every six months through the hospital cochlear implant center.

Resources: Understanding Hearing Ability

Internet:

Auditory Neuropathy Simulation http://www.ucihs.uci.edu/hesp/Simulations/simulationsmain.htm

Baha System http://cochlearamericas.com/products/2013.asp

Center for Disease Control: Unilateral hearing loss http://www.cdc.gov/ncbddd/hearingloss/conference.html

HearingCenterOnline.com: What does hearing loss sound like? http://www.hearingcenteronline.com/sound.shtml

Phonak: Hearing loss demos. http://www.phonak.com/consumer/hearing/hearinglossdemo.htm

Raising Deaf Kids: Types of hearing loss. http://www.raisingdeafkids.org/hearingloss/types

University of Wisconsin-Whitewater/Scott Bradley: Hearing loss sampler (On-line hearing loss simulations). http://facstaff.uww.edu/bradleys/radio/hlsimulation