sign in sign up
<<
Home , Audiology, Cochlea, Hearing range

ANATIONAL RESOURCE CENTER GUIDE FOR FOR EARLY HEARING ASSESSMENT DETECTION & & MANAGEMENT INTERVENTION

Chapter 5 101: An Introduction to Audiology for Nonaudiologists Terry Foust, AuD, FAAA, CC-SLP/A; & Jeff Hoffman, MS, CCC-A

Parents of young Introduction What is an audiologist? children who are arents of young children who are An audiologist is a specialist in hearing identified as deaf or hard identified as deaf or hard of hearing and balance who typically works in of hearing (DHH) are P(DHH) are suddenly thrust into a either a medical, private practice, or an suddenly thrust into a world of new concepts and a bewildering educational setting. The primary roles of world of new concepts array of terms. What’s a or ? an audiologist include the identification and a bewildering array What does sensorineural mean? Is a and assessment of hearing and balance moderate one to be concerned problems, the habilitation or rehabilitation of terms. about, since it’s only moderate? What’s of hearing and balance problems, and the a tympanogram or a ? prevention of hearing loss. When working These are just a few of the many questions with infants and young children, the that a parent whose child has been primary focus of audiology is hearing. identified as DHH may have. In addition to parents, questions also arise from Audiologists are licensed by the state in professionals and paraprofessionals who which they practice and may be members work in the field of early hearing detection of the American Speech-Language- and intervention (EHDI) and are not Hearing Association (ASHA), American audiologists. The purpose of this chapter Academy of Audiology (AAA), Academy is to provide basic answers to these and of Doctors of Audiology (ADA), or the other important questions about the field Educational Audiology Association of audiology. (EAA). Some audiologists hold the

eBook Chapter 5 • An IntroductioneBook to Audiology Chapter for 5 • Nonaudiologists Audiology 101: • 5-1 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

American Board of Audiology’s Pediatric and fiber tissue. It is attached to the wall of Audiology Certification. Others the canal and also to one of the bones may hold the ASHA Certificate of Clinical of the . The seals the Competence in Audiology (CCC-A). middle ear from the environment. vibrates the eardrum and is changed to Several online search tools are available to mechanical energy. find an audiologist: The middle ear is a hollow space that • Early Hearing Detection and is separated from the by the Intervention Pediatric Links to eardrum and contains the three smallest Services (EHDI-PALS) bones in the body. travel through • Early Hearing Detection and the and are transferred to the Intervention (EHDI) program, also by these bones (). The known as the Newborn Hearing three bones are the hammer (), Screening Program, in each state anvil (), and stirrup (). They • ASHA are connected by ligaments, and two of • AAA the bones have tiny muscles attached. The shape and arrangement of the ossicles What are the parts of the ear? increases the strength of the mechanical energy. When loud sounds are present, the tiny muscles contract and reduce the A basic understanding of the parts of strength of those sounds. This helps protect A basic understanding the and how they work the ear from damage due to loud sounds. of the parts of the is helpful to understanding the different auditory system and types of hearing loss. There are four main The is also part of how they work is helpful parts of the auditory system: the middle ear system and connects the middle ear space to the back of to understanding • Outer ear the throat. The Eustachian tube is the different types of • Middle ear normally closed but opens periodically hearing loss. • Inner ear to keep the air pressure in the middle • Central auditory system ear space the same as the surrounding environment. An example of the Each part plays an important role in Eustachian tube working occurs when transferring and processing sound, so that a yawn or a swallow “unstuffs the ” the can recognize and interpret what a particular sound means.

The outer ear consists of three major parts: Figure 1 of the Auditory • Pinna • Ear canal System • Eardrum (tympanic membrane)

The pinna is the part of the ear that we see and contributes slightly to locating a sound. The ear canal, which is about an inch long and S-shaped, channels sound toward the eardrum. The ear canal produces which helps to clean the ear canal of debris. The last part of the outer ear is the eardrum which is the boundary between the outer and the middle ears. The eardrum is a very thin membrane, consisting of layers of skin

eBook Chapter 5 • Audiology 101: • 5-2 NATIONAL CENTER FOR HEARING ASSESSMENT & MANAGEMENT

when flying in an airplane. Sometimes What are the types of If a child is born with a the tissues of the Eustachian tube significant malformation become swollen from a cold or hearing loss? of the outer and/or upper respiratory infection, and it middle ear that prevents doesn’t open and close well—causing Hearing losses can be categorized by when problems in the middle ear. It’s they occur. A hearing loss that is present at or reduces the sounds possible for infection to spread from birth is called a congenital hearing loss. But being conducted to the the nose and throat area through the hearing loss can and does occur at any time inner ear, surgery may Eustachian tube to the middle ear, and can be called later-onset or acquired. If be possible. The child’s which is one of the causes of middle a hearing loss continues to get worse, it is hearing ability may or ear infections. called a progressive hearing loss. may not improve after The third part of the auditory system is the One of the ways that an audiologist surgical treatment. inner ear. The inner ear has two sections: describes a hearing loss is by how many one that is responsible for balance and ears are involved. If a hearing loss is only the other for hearing. The hearing part of in one ear, the loss is called a unilateral the inner ear is the . The cochlea (one-sided) hearing loss. If there is hearing is a snail-shaped space in the skull that loss in both ears, it is described as a contains very tiny structures that convert bilateral (two-sided) hearing loss. mechanical energy into electrical impulses needed for the nervous or central auditory The different types of hearing loss are system. The cochlea is divided by tissue primarily based on what part of the ear is structures into three channels, each of preventing a sound from being transferred which is filled with fluid. There are many and processed effectively. thousands of tiny hair cells () that are embedded in the tissue that divides the three sections. The hair cells bend slightly in response to different kinds A conductive hearing loss occurs because of sounds, depending on where they are problems in the outer and/or middle ear located in the cochlea. When bent, the keep the sound from being “conducted” hair cells create electrical signals that are well. Conductive hearing losses can be then sent to the central auditory nervous either temporary (transient) or permanent. system. Medical treatment of the underlying cause of the temporary conductive hearing loss The last part of the auditory system may result in the hearing returning to consists of the auditory nerve and the normal or near normal. For example, if central auditory system in the brain. The the ear canal is plugged with earwax or an electrical nerve impulses produced in the object of some sort, some hearing loss will cochlea by the hair cells are transmitted occur until the blockage is removed. The and processed along the auditory nerve amount of hearing loss would be similar to that consists of about 25,000 nerve fibers. having an in your ear canal. The signal continues through the brain stem to the of the brain. It At least 80% of children have three or more is in the cortex that sounds are interpreted episodes of ear infections () based on experience and association and before 3 years of age (Roberts & Hunter, that meaning is assigned to sounds that 2002). These ear infections can be painful, travel through the outer, middle, and inner and if the middle ear space fills with fluid, ears. a temporary conductive hearing loss can occur. Middle ear infections left untreated Auditory Transduction by Brandon Pletsch can cause some other middle ear problems is an excellent 7-minute animation on that may result in a permanent loss. YouTube about the different structures of the auditory system, how they work, and If a child is born with a significant how each contributes to hearing. malformation of the outer and/or middle

eBook Chapter 5 • An Introduction to Audiology for Nonaudiologists • 5-3 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

ear that prevents or reduces the sounds How often does hearing loss being conducted to the inner ear, surgery may be possible. The child’s hearing ability occur in young children? may or may not improve after surgical treatment. Many children have a temporary conductive hearing loss due to ear Sensorineural (or Sensory) Hearing Loss infections, but how many have a permanent hearing loss? Each year, state A sensorineural (or sensory) hearing loss EHDI programs send the results of their from problems in the cochlea or inner newborn hearing screening program ear is almost always permanent. There are to the Centers for Disease Control and many different causes of a sensorineural Prevention (CDC). In 2013, over 97% of hearing loss. Some losses can be genetic the babies born in the United States had or syndromic—the result of some their hearing screened within the first few medications, infections, high fevers, or days of life, and 5,253 of them were born head trauma. with a permanent congenital hearing loss. This is a prevalence of 1.5 per thousand spectrum (15 of every 10,000) babies who received Nationally, almost one- disorder (ANSD) describes a disordered a newborn hearing screening. Those are third of the newborns transmission of the electrical signal only the babies with a confirmed hearing who don’t pass the along the acoustic nerve. ANSD— loss. Nationally, almost one-third of the newborn hearing sometimes called auditory neuropathy/ newborns who don’t pass the newborn dyssynchrony—is relatively rare in the hearing screening aren’t getting the screening aren’t getting well-baby population and somewhat recommended follow-up evaluations, so the recommended more prevalent in babies who have there are likely more congenital hearing follow-up evaluations. spent time in the neonatal intensive care losses than are reported (CDC, 2015). unit. About 40% of the newborns reported by the Mixed Hearing Loss state EHDI programs to the CDC for 2013 had a , while 60% A mixed hearing loss has both of them had a bilateral hearing loss. Only a conductive component and a 14% of the babies born with a permanent sensorineural component. The hearing loss had a conductive hearing loss. conductive component is the result of About 62% of the permanent congenital a problem in the outer and/or middle hearing losses reported to the CDC were ear, while the sensory or sensorineural sensorineural—by far the most common portion results from a problem in the type. Permanent congenital mixed hearing inner ear. losses are somewhat rare—about 8% of the results reported to CDC in 2013. ANSD Central Hearing Loss is also rare, accounting for only 5% of the permanent congenital losses (CDC, 2015). Central auditory processing refers to how well the transmits Hearing loss can and does occur at any time and uses auditory information. Disorders in a person’s life. Eiserman et al. (2008) of central auditory processing can include found that 1.5 per thousand (15 of every problems with determining where a sound 10,000) children up to 3 years of age who had is coming from and excessive difficulty been screened using otoacoustic emissions understanding speech and auditory technology in Early Head Start programs signals in poor listening conditions, had a permanent hearing loss that hadn’t such as noisy settings. These disorders been identified earlier. Similarly, Bhatia may coexist with other disorders, such et.al. (2013) identified 2.5 per thousand (25 as language impairment and learning of every 10,000) with a newly identified disorders, but is not the result of those permanent hearing loss in children birth to disorders. 3 years in a screening program at federally-

eBook Chapter 5 • Audiology 101: • 5-4 NATIONAL CENTER FOR HEARING ASSESSMENT & MANAGEMENT

funded health clinics. Foust et al. (2013) school-age children have a hearing loss The rate of permanent found a similar rate of previously unidentified (Niskar et al., 1998). hearing loss continues permanent hearing loss 1.2 per thousand (12 to climb as children get of every 10,000) children up to 5 years of age What causes permanent in federally-funded health clinics. older. It is estimated hearing loss? that as many as 14.9% of In 2006, Morton and Nance published school-age children have Newborn Hearing Screening - A Silent Morton and Nance (2006) reported that a a hearing loss. Revolution, which identified the causes of mutation of the GJB2 gene was responsible permanent hearing loss at birth and also for 21% of congenital permanent hearing at 4 years of age. As can be seen in Figure losses (see Figure 2). That, however, 2, the incidence of permanent hearing loss was only one of the genetic causes of at birth was nearly 2 per thousand (186 congenital hearing loss. Causes of hearing per 10,000). By 4 years of age, as shown loss associated with various syndromes, in Figure 3, the incidence of permanent including Pendred’s syndrome, accounted hearing loss increased to about 3 per for 17% of congenital hearing loss, and an thousand (270 per 10,000). additional 30% of hearing loss at birth was due to unspecified nonsyndromic genetic The rate of permanent hearing loss factors. Overall, genetic factors accounted continues to climb as children get older. for 68% of the congenital permanent It is estimated that as many as 14.9% of hearing losses. Figure 2 Figure 3 Causes of Hearing Loss at Birth at 4 Years of Age

(Morton and Nance, 2006)

eBook Chapter 5 • An Introduction to Audiology for Nonaudiologists • 5-5 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

Congenital cytomegalovirus (CMV) is a 6 months. By 6 months of age, the child leading cause of congenital hearing loss, will be enrolled in early intervention accounting for 21% of the hearing losses services. present at birth. About half of children with hearing loss due to CMV show other Why are these targets so important? complications of congenital CMV, such as Because the rate of growth and vision loss; small head size; or problems development in the first year of a with the liver, spleen, or lungs. baby’s life is unmatched at any other time during postnatal (after birth) By 4 years of age, over 50% of the hearing development. These findings are losses were due to genetic factors (see supported by various brain-imaging Figure 3). Congenital CMV still accounted techniques. Imaging studies, such as for about one-fourth of all permanent this Positron Emission Tomographic hearing losses, but there were some late- (PET) scan (see Figure 4), show that onset hearing losses due to CMV. the brain rapidly matures in an orderly fashion during the first years of life. Why is it important to screen The orange-red color represents the rapid growth from 1 month to 1 year hearing as early as possible? of age.

It is critical to understand the importance The sooner we can find of discovering a hearing loss as soon as a hearing problem, the possible. The sooner we identify a hearing Figure 4 sooner we can start to problem, the earlier the intervention to PET Scan Showing Brain help, and the greater minimize the impact of the hearing loss and the success of language strategies to maximize use of the remaining Maturational Changes with Age hearing sensitivity can be implemented. and communication Simply stated, the sooner we can find a development. hearing problem, the sooner we can start to help, and the greater the success of language and communication development.

There are formal recommendations for the minimum ages and time periods for each step in the process for the identification and diagnoses of hearing loss and the necessary intervention and followup. The Joint Committee on Infant Hearing (JCIH, 2007) 2007 Position Statement recommends the following newborn hearing screening guidelines: During this period, the infant brain 1 month. By 1 month of age, a is developing, and tiny synapses, hearing screening is completed. which are biological electrical connections, are forming. The amount 3 months. By 3 months of age, of stimulation a child receives directly the child failing or referring a impacts the number of synapses hearing screening will have a formed within the brain. This includes complete diagnostic hearing the hearing, speech, and language evaluation with audiology and centers of his or her brain. The creation otolaryngology examinations. of synapses is virtually complete after If a hearing loss is diagnosed, the the first 3 years of life, thus those child will be fit with hearing aids as per years are the most important in brain the parents choice. development.

eBook Chapter 5 • Audiology 101: • 5-6 NATIONAL CENTER FOR HEARING ASSESSMENT & MANAGEMENT

How is a hearing loss These tests are sequential—moving from the outer part of the ear (peripheral) to diagnosed? more internal (inner ear) to more central and then to the whole auditory system. It A hearing loss is detected by screening and is important to remember that no one test testing the auditory system through use can stand alone. It takes an assessment of all of age-appropriate hearing tests. Hearing the elements of the auditory system—or a tests are used to determine four things: “battery of tests”—to confirm hearing status.

Significance of the Hearing Loss Immittance ( and Acoustic Reflexes) This means determining if the hearing loss is mild, moderate, moderate-to-severe, Tympanometry is a measure of middle severe, or profound in nature. ear function. It provides information on the status (condition and function) of the The Kind or Type of Hearing Loss middle ear system. It evaluates the normal occurring pressures of the middle ear This means determining if the hearing loss system (the pressure you feel change when is caused by problems getting the sound you “pop” your ears), as well as the needed into the inner ear where it can then be mobility or movement of the ear drum or heard (conductive hearing loss), or if it tympanic membrane. It is conducted by is a problem in the inner ear or beyond placing a small probe with a soft rubber tip in the pathways of the auditory system in the ear canal and introducing pressure (sensorineural hearing loss). changes along with a sound “tone” into the ear canal. An abnormal result is Configuration of the Hearing Loss consistent with a problem in the transfer of sound into the auditory system—known This means determining if hearing is better or as a conductive hearing loss. You may worse at some pitches (). Hearing have experienced a conductive hearing loss can be equal or flat across all the pitches loss when you had a head cold or an ear or better at either the low or high pitches. infection where sound was muffled.

Make Intervention Recommendations Tympanometry and measurement of acoustic reflexes are a valuable component And decisions on treatment strategies that of the audiological evaluation. In evaluating most benefit the child. hearing loss, immittance audiometry permits a distinction between sensorineural What tests are used to and conductive hearing loss. In addition, in a primary healthcare setting, tympanometry determine hearing? can be helpful in making the diagnosis of otitis media by demonstrating the presence There are four primary tests for assessing of middle ear fluid (effusion). hearing. They are: Tympanometry helps identify middle ear conditions, such as: 1 Immittance Audiometry. A test of middle ear function. • A hole or perforation of the eardrum. Otoacoustic Emissions (OAE). A test of inner ear function. • Fluid behind the ear drum. 2 • Negative air pressure behind the ear Auditory Brainstem Response (ABR). A test of neural pathways of the drum. auditory system. • Normal ear drum movement. 3 Behavioral Testing. Assessment of the function of the whole auditory In summary, tympanometry is an objective 4 system from initial sound stimulation to an intentional response. test of middle ear function. It is not a test

eBook Chapter 5 • An Introduction to Audiology for Nonaudiologists • 5-7 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

of hearing sensitivity but rather a measure are easiest to test when they are very of acoustic (sound) energy transmission young or over the age of 18 to 24 months. through the middle ear. As such, it is not Testing children between 6 months of age used to assess the sensitivity of hearing and 2 years of age may require the use but the function of the middle ear system of distractions with appropriate toys or and its resulting impact on hearing. using other strategies. As with all tests, The middle ear system not functioning OAE testing has some limitations—one properly can lead to a problem in the of which is that it does not provide transmission of sound energy and result information about the degree or severity of in a conductive hearing loss. The presence a hearing loss. Another limitation is that, or absence of acoustic reflexes can also be depending on test settings or parameters, very helpful in the diagnosis of the nature it may not detect minimal or slight hearing of a hearing loss. The results of these tests losses. should always be viewed in conjunction with the other hearing tests. ABR Test (Auditory Evoked Response)

OAE Testing ABR tests assess the function of the higher auditory system by measuring the reaction OAE testing is a measure of inner ear of the parts of a child’s nervous system The middle ear system function. Measurement of OAEs are a that affect hearing (auditory pathways). not functioning properly relatively recent addition to the audiologic More simply put, ABR testing measures can lead to a problem test battery. Even though the existence of the hearing nerve’s response to sounds. in the transmission of emissions was discovered by David Kemp The ABR test is safe, can be automated for sound energy and result in England in the late 1970s, it was not screening purposes, and is painless. seen as a routine part of clinical testing in a conductive hearing until the late 1990s. Notice that we are progressing from the loss. “outside in.” In other words from the OAEs are a measurement of normally outer and middle ear system, to the inner produced sound responses generated by ear’s function, and then to the auditory very small hair cells in the cochlea. These pathways in the brain. ABR testing is responses are measured and recorded completed by placing three to four small in the ear canal by placing a small probe recording discs (electrodes that are with a soft rubber tip into the ear and connected to a computer) on the child’s providing sound stimulation. A very small head and near his or her ears. Small microphone records and measures the tiny earphones are placed into the child’s ear response (emission) obtained in direct canal, and sounds (usually clicks) are response to the stimulation. Most normal presented to stimulate the auditory system. healthy inner ears have an OAE response. Small waveforms that constitute responses to the stimuli at certain locations within The presence of OAEs indicates that the brain are recorded by the computer. the middle ear system is most likely The presence or absence of waveforms functioning appropriately (sound was at specific sound levels and frequencies transmitted normally), and the the inner can confirm and help describe a hearing ear (outer hair cells) are functioning loss. We can simulate the ear and record normally. Conversely, if there is no responses from the brainstem that can recordable OAE, then there may a confirm either normal hearing or a problem with one or both (middle ear hearing loss. and/or inner ear) systems (see “How OAEs Work” for a quick tutorial on OAE The ABR test is sensitive to movement. testing). Therefore the child being tested must be still. The ABR test can be completed only if OAE testing can be done with people of the child is sleeping or lying still—relaxed any age, but the response is very robust and with eyes closed. Some factors to in infants and young children. Children consider in this regard are:

eBook Chapter 5 • Audiology 101: • 5-8 NATIONAL CENTER FOR HEARING ASSESSMENT & MANAGEMENT

• Newborns are easily tested during • A close estimate of the child’s hearing ABR testing is the normal and natural sleep. If a child levels (thresholds). The softest intensity most commonly used is younger than 6 months of age, the level at which the ABR responses appear auditory-evoked ABR test usually can be done while he roughly correspond to the child’s hearing potential test. The ABR or she naps. level for each range tested. This electrophysiologic response is slightly is valuable for use with • For children between the ages of 6 higher than the actual hearing levels. infants and young months and 7 years, the ABR test is children. done under sedation, which means • Evaluation of nerve conduction that the child will need medication to delays (timing) provide additional help him or her sleep through the test. information on how the sound signal ABR tests requiring sedation are most is processed for meaning. often done in a same-day outpatient surgery center. Behavioral Testing

• If the child is older than 7 years, the Behavioral testing requires an ABR test can often be done while observable response to sound from the child is awake, relaxed, and lying the child. The child and the parent (or still. The test is usually done by the caregiver) is seated in a sound-treated audiologist in a quiet setting, such as a booth. Sounds of varying intensity are special sound-treated suite. presented through calibrated speakers or earphones. The sounds may consist of When sedation is needed, there are speech sounds as well as specific tones special restrictions or rules for eating of different frequencies that are critical and drinking that must be followed in to hear speech sounds. The audiologist the hours before the test. The test itself records the child’s responses to the softest takes about 1 to 1.5 hours, but the entire sounds and plots them on a graph called appointment will take about 2 hours an . without anesthesia, and up to 4 hours due to the recovery time if the child needs Behavioral hearing tests include sedation. the following methods for specific developmental ages: There are different types of auditory- evoked potentials that audiologists will • Behavioral observation audiometry use depending upon the situation. ABR is (BOA) is used for developmental the most commonly known and is used in ages of 0 to 5 months. The audiologist both automated newborn screening and observes and records the child’s diagnostics. While it is not in the scope of responses to sounds. Responses may this chapter to go into detail on the various consist of quieting, eye widening, types of evoked potentials, they are named startle, etc. These responses must or labeled based on where in the auditory be consistent, repeatable, and pathway the response occurs. The responses appropriately correlated to the are expected to occur within certain presentation of a sound. specific timeframes and are measured in milliseconds. The further “up” in the system, • Visual reinforcement audiometry the longer it takes to see the response. The (VRA) is used for developmental ages amount of time lapsed or how long it takes of 6 months to 2 years. The audiologist for the response to occur is called latency. observes and records when the child turns to the sound and gives ABR testing is the most commonly used a visual reinforcement or reward that auditory-evoked potential test. The ABR is timed to the response. The reward is valuable for use with infants and young is typically either a toy or puppet that children, because it provides the following lights up and/or moves to reinforce information: the child’s response.

eBook Chapter 5 • An Introduction to Audiology for Nonaudiologists • 5-9 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

• Conditioned orientation reflex (COR) are lower-pitched sounds, with the lowest audiometry is the same as VRA but pitch on the audiogram being 125 Hz. As includes more than one sound source and you move to the right, toward 8000 Hz, puppet reinforcer used, such as one on the sounds get higher in pitch. left and one on the right. Many parents describe it as a “sound finding game.” The intensity or is shown along the left side of the audiogram. It is • Conditioned play audiometry (CPA) is measured in —often abbreviated used for children from 2 to 3 years of age as dB. As you move down the audiogram, depending on individual development. the louder a sound must be made to obtain The audiologist establishes a “listening a response and establish the threshold. For game” by using toys to maintain the example, a 10 dB sound is softer than a child’s attention and focus to the whisper for a person with normal hearing, listening task. For example, the child while a 120 dB sound is as loud as a jet holds a block, listens for the sound, and airplane. Familiar sounds are plotted drops the block in a bucket when the on the audiogram for demonstration sound is heard. This is no different purposes, indicating the approximate than raising one’s hand in response to pitch and loudness levels that these sounds the sound, but the toys establish and occur. For example, a lawn mower is a very maintain the child’s interest in the loud, low-pitched sound, while a ’s listening task better than handraising. chirp is a soft, high-pitched sound. Once the child understands the game, testing can get underway.

• Conventional audiometry is used Figure 5 for children ages 5 years and older. Audiogram with Speech and The child raises his or her hand or provides verbal response (i.e., “beep” Environmental Sounds or “I hear it”) in response to the presentation of the various sounds. This is the same standard that you may have had as an adult.

What is an audiogram?

Audiologists record a person’s hearing During a hearing test, the ability on a sound chart or graph called softest levels (thresholds) an audiogram (see Figure 5). Although an that sounds or tones of audiogram is not typically used to record a different frequencies can baby’s hearing evaluation results, it is useful to understand it, because it will be used to be heard are measured record a young child’s hearing ability once and recorded for each ear they are able to reliably provide an observable on the audiogram. response to sound (behavioral testing).

During a hearing test, the softest levels (thresholds) that sounds or tones of different Hearing loss is not “all or nothing” but frequencies can be heard are measured and has various degrees—just as vision does. recorded for each ear on the audiogram. Remember the loudness level that a sound Frequency is measured in Hertz, often can just barely be heard is the threshold. abbreviated as Hz. The frequencies on the The audiogram is set up, so that if a sound is audiogram range from 125 Hz to 8000 Hz. presented at a very soft level and heard, this Sounds on the left portion of the audiogram threshold or detection level is marked at the

eBook Chapter 5 • Audiology 101: • 5-10 NATIONAL CENTER FOR HEARING ASSESSMENT & MANAGEMENT

top of the audiogram. If the sound has to be In other words, for a person with normal made very loud to be detected, the threshold hearing at the different pitches (frequencies), is marked near the bottom of the audiogram. the tone can be detected at very soft levels. A In this way, the degree of hearing loss can be person with normal hearing would be able visualized on the audiogram. to easily hear all of the louder sounds, such as all of the speech sounds represented in In this variation of the audiogram, the the “speech banana,” and the other noises in yellow-shaded area represents where the Figure 5, such as a bird chirp. sounds of speech at a soft conversational level take place. If you look closely at The range of thresholds in the aqua band this area—sometimes called the “speech represents a minimal hearing loss. Some of banana”—you will notice that the sounds the speech sounds on the “speech banana,” of speech occur in the loudness range such as the “f” and “th,” are no longer from approximately 15-50 dB and the detectable. So a child with a minimal loss frequency range from approximately wouldn’t be able to hear the difference 250 to 8000 Hz. Vowels tend to be lower between “fin” and “thin” based on an pitched and louder than consonants. auditory signal alone, even in the best of listening environments. All the other speech What are the degrees of sounds are being heard at a softer level. Hearing loss is not “all or hearing loss? A mild hearing loss—shown with the nothing” but has various lavender band—occurs when the hearing degrees—just as vision Normal hearing for children is in the range thresholds are between 25-40 dB. We may does. below 15 dB, corresponding to the orange think that “mild” is, well, mild . . . but notice band on the audiogram (see Figure 6). how many speech sounds displayed in the speech banana are not being heard. So “mild” has a significant impact on understanding, especially for a very young child who has Figure 6 not yet acquired language and can’t “fill in Audiogram and Hearing Loss the blanks” like adults with a long history of access to speech and language.

The green band shows the range of hearing thresholds for a moderate hearing loss. Notice how the speech sounds for soft conversational speech are nearly all inaudible, and that normal conversational levels (red dotted line) are perceived as a whisper. Moderate? Not when you consider the impact this degree of hearing loss would have on a child’s access to everyday speech during critical periods of language development.

The pink bar on this audiogram shows the threshold levels for a moderate-to-severe hearing loss, which is 55 dB to 70 dB. Most if not all of typical conversational speech would not be detected with this degree of hearing loss.

The blue area indicates a severe hearing loss with thresholds in the 70 to 90 dB range. The tan band at the bottom of the audiogram shows thresholds in the profound hearing loss range.

eBook Chapter 5 • An Introduction to Audiology for Nonaudiologists • 5-11 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

With these degrees of hearing loss, gaps, but very young children don’t have typical conversation as well as many the advantage of that experience. environmental sounds would be inaudible without amplification. There are many unique configurations of hearing loss. Some have more hearing Many hearing losses are not “flat” with loss at the lower frequencies, while others similar thresholds across the frequency have more loss in the highs. Others range but instead have different thresholds have about the same degree of hearing at various frequencies. loss at all frequencies. Some may have normal hearing at some frequencies People with a long Figure 7 is an example of a common and a significant hearing loss at others. history of accessing configuration of hearing loss with Every hearing loss makes some sounds in speech and language different degrees of hearing loss at various everyday conversations more difficult to can fill in some of the frequencies. This is an example of a mild- access and therefore makes understanding gaps, but very young to-severe sloping hearing loss. Some more challenging. Here are two resources children don’t have speech sounds are audible to this person, that simulate different degrees of hearing but many are not, so there’s a lack of clarity loss and are helpful for a person with the advantage of that with many words and conversations. normal hearing to experience the effects of experience. People with a long history of accessing hearing loss on understanding speech: speech and language can fill in some of the • Flintstones Cartoon by House Ear Institute • Demonstrations by Success for Kids Figure 7 with Hearing Loss Audiogram Example: Mild-to-Severe What are the treatment and Sloping Hearing Loss intervention options for children with hearing loss?

Once a child has been diagnosed with a hearing loss, it is necessary to begin treatment and intervention as quickly as possible. Intervention includes three key areas:

Surgical Intervention. Evaluation for any 1 medical/surgical intervention that may x or repair a structural problem contributing to the hearing loss. Ampli cation/Cochlear Implants. Maximizing any 2 residual hearing through ampli cation or cochlear implants. Early intervention for communication development 3 via the parents’ choice of communication modalities (verbal, manual, combination, etc.).

eBook Chapter 5 • Audiology 101: • 5-12 NATIONAL CENTER FOR HEARING ASSESSMENT & MANAGEMENT

Surgical Intervention • Lack of benefit from amplification.

The first thing to consider is whether • A minimum age of 12 months but medical intervention, including surgery, sometimes younger with approval. may be helpful. In some cases, surgical intervention could assist or repair a • A minimum of bilateral severe-to- problem, such as a closed ear canal profound hearing loss. (atresia) where all the other parts of the ear are normal. In these cases, the child • Must have no medical would be evaluated for surgery, and, contraindications. if appropriate, the surgery would be completed. The child’s hearing would be • Must have available appropriate evaluated afterwards and compared to educational and intervention support the prior results to quantify improvement services for post-cochlear implant and determine if further intervention is aural re/habilitation. indicated. • Evaluation of family factors, such Amplification as motivation to followup. and provide the required post-implant The second intervention to consider is education and intervention services It is important to the fitting of amplification (hearing aids) ,and that the family has realistic understand that it is to enable the child to make maximum expectations. possible to proceed use of residual hearing capacity. The vast majority of children with hearing Parents and primary with amplification as providers should confer with a cochlear soon as a diagnosis of loss have some level of residual hearing, and amplification with hearing aids implant team to ask questions and hearing loss is made, but is the appropriate intervention. The determine a child’s candidacy. Current the parents may not be JCIH (2007) recommends all infants Federal Drug Administration (FDA) emotionally prepared for diagnosed with permanent hearing loss information and candidacy requirements such a step. should be fit with amplification within can be found at: 1 month of confirmation of the hearing loss. • http://www.fda.gov/MedicalDevices/ ProductsandMedicalProcedures/ It is important to understand that it is ImplantsandProsthetics/ possible to proceed with amplification CochlearImplants/default.htm as soon as a diagnosis of hearing loss is made, but the parents may not be • http://www.audiology.org/ emotionally prepared for such a step. publications-resources/document- It is important that parents receive library/cochlear-implants-children encouragement as they take this first step in the habilitation of their child’s hearing How does a cochlear implant work? loss. A cochlear implant uses special electronic technologies to take the Cochlear Implants place of the nonworking parts in the inner ear and is designed to mimic When hearing loss is profound with natural hearing. Here is a brief little or no residual hearing, and hearing overview of the parts of an implant aids have not provided any benefit, a and how it works. For more detailed cochlear implant may be considered. information, see the Cochlear Implant There are specific criteria that must be and Cochlear Implant Candidacy met for a child to receive an implant. The chapters of this publication. criteria for candidacy has changed over time. However, the current criteria is as A cochlear implant has several parts (see follows: Figure 8) that work as follows:

eBook Chapter 5 • An Introduction to Audiology for Nonaudiologists • 5-13 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

Early Language and Communication Figure 8 Intervention

Parts of a Cochlear Early intervention is crucial for Implant communication and overall development. Audiologists work closely with a team of professionals that often includes early interventionists, deaf mentors, parent infant programs, educators of the deaf and hard of hearing, speech language pathologists, and therapists with different communication specialties. Treatment and intervention should be focused on the following:

• Meeting overall developmental milestones. • Communication modalities, such as oral, auditory verbal, American Sign Language, cued speech, total communication, and others. • Emotional development for the child and support for the family. • Social development. • Cognitive development.

To assist early interventionists and contribute Sound Processor to the success of treatment and education plans, audiologists provide education on how to troubleshoot the child’s hearing aids Sound is picked up by a tiny microphone that is sensitive to the direction or cochlear implant to ensure the child is from which the sounds come. For example, it may pick up more sounds hearing optimally. In addition, the audiologist from in front of the user and fewer from behind him or her. This external provides very important information on sound processor captures the sound and converts it into digital signals. what the child can or cannot hear with Digital Signals either hearing aids or cochlear implant. This detailed information includes describing what frequencies and speech sounds the child hears The digital signals are sent through the skin to the internal implant. This and how well he or she hears them. is done with technology similar to the way a radio station broadcasts its signal but on a much smaller scale. Information regarding audibility of speech is important for many reasons. For instance, Electrode Array some speech sounds are louder (voiced), and others are quieter (no voicing). An The internal implant has a long wire that threads through the length of example of this would be the sounds “B”and the cochlea. Electrodes placed along the wire convert the digital signals “P.” The sound “B” in isolation is made into electrical energy and stimulate areas corresponding to different with the lips with sound vibration from frequencies. the vocal cords. In contrast, the sound “P” is made the same way with the lips but has Hearing Nerve no voicing from the vocal cords. Try saying both in an alternating fashion a few times! This electrical energy stimulates the hearing nerve, thereby bypassing If one were relying on visual cues, they the damaged hair cells—or the cause of the hearing loss—and the brain would look the same. We differentiate the learns to perceive the signals as sound. two sounds by hearing the voicing. In this example, the audiologist can help the family and early intervention team understand if

eBook Chapter 5 • Audiology 101: • 5-14 NATIONAL CENTER FOR HEARING ASSESSMENT & MANAGEMENT

the child can hear the difference and at what What other intervention Invite participation distances from the speaker or sound source. in your strategies can audiologists screening efforts in Distance information is crucial. Sound help facilitate? newborn hearing travels and works in a predictable way. For example, every time you decrease the screening and early distance between a sound and its source Other intervention strategies to consider childhood hearing by half, the sound increases in loudness include maximizing the learning screenings. Work by 6 dB. There is a saying in the world environments of hearing-impaired collaboratively, and of habilitation of hearing loss that goes, children. Especially important are the always, always keep “Come closer to me by 6 dB,” suggesting auditory and visual environments—an asking questions! that we interact at optimal distances for audiologist can help with structuring these hearing. The converse is also true in that environments. Some examples include: every time you increase the distance by half, the sound decreases in loudness. Maximize the Auditory Environment

The audiologist can help determine the • Ensure the amplification system is working. best distance from the sound source, • Ask the audiologist to train early interventionists, which in most cases is where the educational staff, and others about the devices communication partner, such as the child’s (hearing aids and or cochlear implants). parents or the early interventionist, should • Thoughtful placement to learning centers. be located. If one were to draw a circle • Be aware of and reduce background noise. around the child where the majority of • Make sure the child’s attention is focused on the speech sounds are audible, this would be speaker and talk naturally and clearly. referred to as the child’s “listening bubble.” All important communication should Highlight the Visual Environment occur within the child’s listening bubble.

One can assess and determine a child’s • Position children with hearing loss, so they can listening bubble (optimal ) easily focus on activities. by using what is referred to as the “Ling 6 • Be sure lighting is appropriate. Sound Test” (named after Dr. Daniel Ling, • Direct to auditory language information. a pioneer in the area of aural habilitation). • Ensure that child positioning in relationship to To do the test, you teach the child to imitate the teacher promotes positive social relationships or provide a response to sound, specifically while enhancing learning. the speech sounds of “mm,” “ah,” “ooh,” “ee,” “shhh,” and “sssss,” which phonetically are written as /m, a, u, I, sh, s/. The sounds go Conclusion from the lowest frequency speech sounds to the highest. The speech sounds move to the Audiology is the study of hearing. front of the mouth, and the last two (“shhh” Audiologists screen, diagnose, and manage and “sssss”) are unvoiced. those with hearing loss or other disorders of hearing. Once the child provides an observable response to the sounds, use the sound test Contact your local audiologists for help to find the distances the child hears the whenever you have a question or a need sounds. Start at 20 inches from the child’s for expertise in hearing. You can engage hearing aids, then move to 3 feet, 6 feet, your community audiologists by making and finally to 9 feet. Record the distances outreach efforts either individually or at which all sounds are heard. This will as a group. Invite participation in your allow you to determine the optimal public health screening efforts in newborn distance at which most communication hearing screening and early childhood happens. Ensure you are interacting at the hearing screenings. Work collaboratively, optimal distance for the child. and always, always keep asking questions!

eBook Chapter 5 • An Introduction to Audiology for Nonaudiologists • 5-15 A RESOURCE GUIDE FOR EARLY HEARING DETECTION & INTERVENTION

References

Bhatia, P., Mintz, S., Hecht, B., Deavenport, A., & Kuo, A. (2013). Early identification of young children with hearing loss in federally qualified health centers. Journal of Developmental & Behavioral , 34(1), 15-21. Centers for Disease Control and Prevention. (2015). 2013 annual data Early Hearing Detection and Intervention (EHDI) Program. Retrieved November 19, 2015, from http://www.cdc.gov/ncbddd/hearingloss/ehdi-data2013.html. Centers for Medicare and Medicaid Services (CMS). (2005). CMS manual system, Pub 100-03, Medicare National Coverage Determination, Subject: Cochlear Implantation Transmittal 42. Baltimore, MD: Department of Health & Human Services, Center for Medicare and Medicaid Services. Eiserman, W., Hartel, D., Shisler, L., Buhrmann, J., White, K., & Foust, T. (2008). Using otoacoustic emissions to screen for hearing loss in early childhood care settings. International Journal of Pediatric , 72, 475-482. Foust, T., Eiserman, W., Shisler, L., & Geroso, A. (2013). Using otoacoustic emissions to screen young children for hearing loss in primary care settings. Pediatrics, 132(1), 118–123. Joint Committee on Infant Hearing. (2007). Year 2007 Position Statement: Principles and Guidelines for Early Hearing Detection and Intervention Programs. Pediatrics, 120(4), 898-921. Niskar, A., Kieszak, S., Holmes, A., Esteban, E., Rubin, C., & Brody, D. (1998). Prevalence of hearing loss among children 6 to 19 years of age: The third national health and examination survey. Journal of the American Medical Association, 279(14), 1071-1075. Roberts, J., & Hunter, L. (2002). Otitis Media and children’s language learning. The ASHA Leader, 7, 6-19.

eBook Chapter 5 • Audiology 101: • 5-16