Prevalence of hearing loss increases dramatically with age. National survey results show that in the population of those with hearing impairment, only 2% were born with a hearing impairment; 4% to 6% developed a hearing loss after birth and before 6 years; 11% to 12% developed hearing loss between ages 6 and 19 years; 50% to 64% developed hearing loss between ages 20 and 59 years; and 20% to 30% developed hearing loss at or after the age of 60 (data from the National Health Interview Survey, 2007, retrieved from the National Institute on Deafness and Other Communication Disorders [NIDCD], 2010).

Findings from the National Health and Nutrition Examination Survey indicated that 14.9% of children between 6 and 19 years of age had a hearing loss of at least 16 dB in either low or high frequencies; the majority of these losses were classified as slight (16-25 dB; Niskar et al., 1998). Hearing loss of at least 25 dB at the speech frequencies has been reported in 29% of adults 50-59 years old, in 49% of adults 60-69 years old, and in 63.1% of adults ages 70+ (Agrawal, Platz, & Niparko, 2008; Lin, Thorpe, Gordon-Salant, & Ferrucci, 2011).

• More than 50% of prelingual deafness is genetic. Of the genetic hearing losses, most (70%) are nonsyndromic and, of these, 75%-85% of cases are autosomal recessive (Smith, Shearer, Hildebrand, & Van Camp, 2014).
• The most common cause of intermittent, mild-to-moderate acquired hearing loss in infants and young children is conductive hearing loss associated with otitis media.
• Noise-induced hearing loss is an increasing concern for children and adolescents. Niskar et al. (2001) estimated that 12.5% of U.S. children (ages 6-19) have evidence of noise-induced hearing threshold change.
• In adults, noise and aging are the primary causes of hearing loss. In the North American World Health Organization (WHO) subregion, 9% of all adult-onset hearing loss is likely attributable to occupational noise. A higher percentage (20%) is attributable to occupational noise for adult males with hearing loss between the ages of 15 and 44 (20%) than for males between the ages of 45 and 79 (2%-14%) and females (1%-9%; Nelson, Nelson, Concha-Barrientos, & Fingerhut, 2005).

Signs and symptoms associated with hearing loss-including behaviors of affected individuals-include

• "muffled" hearing,
• asking for repetition,
• tinnitus,
• difficulty attending,
• difficulty understanding speech in noise,
• turning the volume up on the television/music,
• thinking others "mumble,"
• difficulty understanding speech on the telephone,
• difficulty understanding speech, particularly of women and children,
• rhyming mistakes-for example, hearing the high-pitched sound /t/ in the word tin as /f/ in the word fin,
• not participating in activities/isolating one's self,
• speaking too loudly or too softly.

Signs and symptoms in school-age children also include

• poor academic performance,
• delayed language and speech production development,
• behavioral concerns,
• auditory processing problems.

Not all patients will experience each symptom.

Conductive Hearing Loss

Causes of conductive hearing loss include

• fluid in the middle ear (e.g., from upper respiratory infections, otitis media, or serous otitis media);
• poor eustachian tube function;
• perforated tympanic membrane;
• benign tumors;
• head trauma-physical head injury can lead to skull fractures, a hole in the tympanic membrane, and damage to middle ear structures;
• otosclerosis;
• impacted cerumen;
• infection in the ear canal (external otitis);
• swimmer's ear (otitis externa);
• presence of a foreign body;
• absence or malformation of the outer ear, ear canal, or middle ear.

Mixed Hearing Loss

Mixed hearing loss is caused by a combination of one or more causes of conductive hearing loss and one or more causes of sensorineural hearing loss.

Sensorineural Hearing Loss

Causes of sensorineural hearing loss include:

• Noise - the type as well as the level of noise and the length of time spent listening to the noise can create risk for noise-induced hearing loss. See the U.S. Department of Labor Occupational Safety and Health Administration (OSHA) standards for occupational noise exposure, the National Institute for Occupational Safety and Health (NIOSH) criteria [PDF], and the World Health Organization - International Telecommunication Union standard [PDF] for recommendations.
• Genetics-disorders can be autosomal recessive or autosomal dominant. Other, rarer, types of genetic hearing loss include X-linked (related to the sex chromosome) or mitochondrial inheritance patterns. Genetic disorders that include hearing loss include neurofibromatosis 2 and Waardenburg Syndrome (Smith, Shearer, Hildebrand, & VanCamp, 2014).
• Ototoxicity-drugs known to be ototoxic include
  • drugs used in chemotherapy regimens (cisplatin, carboplatin, and nitrogen mustard),
  • aminoglycoside antibiotics (streptomycin, neomycin, and kanamycin),
  • salicylates in large quantities (aspirin),
  • loop diuretics (lasix and ethacrynic acid).
• Head trauma-physical head injury can lead to traumatic brain injury (TBI), skull fractures, and damage to the inner ear.
• Autoimmune inner ear disease (AIED)-AIED occurs when the body's immune system attacks cells in the inner ear that are mistaken for a virus or bacteria and can happen in isolation (as just labyrinthine disease) or as part of other systemic autoimmune disorders. Systemic immune diseases known to have caused AIED include
  • Cogan syndrome,
  • lupus,
  • relapsing polychondritis,
  • Wegener's granulomatosis,
  • polyarteritis nodosa,
  • Sjogren syndrome,
  • lyme disease.
• Bacterial, viral, or parasitic infections, including
  • meningitis,
  • mumps,
  • measles,
  • CMV,
  • labyrinthitis,
  • herpes,
  • toxoplasmosis,
  • syphilis.
• Acoustic neuroma
• Large vestibular aqueduct
• Meniere's disease
• Vascular deficits, including
  • vascular disease associated with mitochondriopathy,
  • vertebrobasilar insufficiency (high blood pressure and diabetes),
  • red blood cell deformability,
  • sickle cell disease,
  • cardiopulmonary bypass.

Relationship Between Hearing Loss and Dementia

Approximately one-third of Americans between ages 65 and 74 and nearly half over the age of 75 have hearing loss (NIDCD, 2010). Many older adults will have both hearing impairment and cognitive loss, and together these losses will affect communication, social participation, and quality of life (Pichora-Fuller, Dupuis, Reed, & Lemke, 2013).

Lin et al. (2013) found that individuals with baseline hearing loss had greater rates of cognitive decline over time than did individuals with normal hearing. Further investigation is needed to clarify this relationship and to determine whether hearing loss is a risk factor for dementia or a sign of early-stage dementia. One hypothesis is that when a hearing loss is present, greater cognitive resources are dedicated to auditory processing, leaving fewer resources for other cognitive processes, like working memory (Peelle, Troiani, Grossman, & Wingfield, 2011). Recent research suggests the possibility of a shared etiological pathway responsible for both hearing loss and dementia (Gallacher et al., 2012).

It is important for clinicians to differentiate between hearing loss and cognitive impairment and to identify when one or both of these conditions are present. See dementia.

Roles and Responsibilities of Audiologists

Audiologists play a central role in the screening, assessment, diagnosis, and treatment of persons with hearing loss. The professional roles and activities in audiology include clinical/educational services (diagnosis, assessment, planning, and treatment), prevention and advocacy, education, administration, and research. See ASHA's Scope of Practice in Audiology (ASHA, 2018).

Appropriate roles for audiologists include:

• educating other professionals on the needs of persons with hearing loss and the role of audiologists in diagnosing and managing persons with hearing loss;
• participating in the development, training of personnel, and management of screening programs;
• conducting a comprehensive assessment of hearing, auditory function, balance, and related systems;
• administration and interpretation of tests for central auditory processing, including behavioral and electrophysiologic measures;
• diagnosing the presence or absence of hearing loss;
• referring the patient to other professionals as needed to rule out other conditions, determine etiology, and facilitate access to comprehensive services;
• evaluating individuals with hearing loss for candidacy for amplification and other sensory devices and assistive technology;
• developing a culturally appropriate audiologic rehabilitative management plan;
• fitting and maintaining amplification and other sensory devices and assistive technology for optimal use;
• evaluating the effectiveness of hearing assistive technology in home, work or school settings;
• creating documentation, including interpreting data and summarizing findings and recommendations;
• providing (re)habilitation services including auditory training and speech reading;
• training and ongoing supervision of support personnel;
• advocating for the communication needs of all individuals, including advocating for the rights and funding of services for those with hearing loss or auditory and/or vestibular disorders;
• counseling persons with hearing loss and their families on the psychosocial aspects of hearing loss and other auditory dysfunction, modes of communication, and processes to enhance communication competence;
• providing prevention information, promoting hearing wellness, and monitoring the acoustic environment;
• collaborating with professionals, family members, caregivers, and others and serving as an integral member of an interdisciplinary team working with individuals with hearing loss and their families and caregivers;
• remaining informed of research in the area of hearing loss and helping advance the knowledge base related to hearing aids;
• remaining informed of federal and state mandates and initiatives (e.g. IDEA, 504 plans, Common Core State Standards, Universal Design for Learning, Multi-Tiered Systems of Support, and approved accommodations) that impact educational programming for students with hearing loss;
• remaining current on new classroom technology and accommodations designed to facilitate access to classroom instruction for students with hearing loss;
• consulting about accessibility for persons with hearing loss in public and private buildings, programs, and services and on the development of products and instrumentation related to the measurement and management of auditory function;
• case management and serving as a liaison for consumers, families, and agencies in order to monitor audiologic status and management and to make recommendations about educational and vocational programming;
• consulting to industry on the development of products and instrumentation related to the measurement and management of auditory function.

As indicated in the Code of Ethics (ASHA, 2010), audiologists who serve this population should be specifically educated and appropriately trained to do so.

Roles and Responsibilities of SLPs

Speech-language pathologists (SLPs) play a role in the identification, screening, assessment, and rehabilitation of individuals with hearing loss and refer individuals suspected of having hearing loss to an audiologist for a complete audiologic assessment. Professional roles and activities in speech-language pathology include clinical/educational services, prevention and advocacy, education, administration, and research. See ASHA's Scope of Practice in Speech-Language Pathology (ASHA, 2016). As indicated in the Code of Ethics (ASHA, 2010), SLPs who serve this population should be specifically educated and appropriately trained to do so.

SLPs have the specialized preparation, experiences, and opportunities to address communication effectiveness, disorders, differences, and delays that result from a variety of factors, including those that may be related to hearing loss. SLPs have the knowledge and skills to address the complex interplay of the areas of listening, speaking, signing, reading, writing, and thinking. Furthermore, they understand how skill expansion in one of these components enhances performance in another area, ultimately contributing to the overall development of literacy and learning.

Appropriate roles for speech language pathologists include:

• understanding the effects of hearing loss on communicative development;
• assessing communication skills and intervention with individuals with hearing loss;
• establishing augmentative and alternative communication techniques and strategies, including developing, selecting, and prescribing such systems and devices;
• providing services to individuals with hearing loss and their families/caregivers (e.g., auditory training, speechreading, speech and language intervention secondary to hearing loss, visual inspection and listening checks of amplification devices for the purpose of troubleshooting, and verification of appropriate battery voltage);
• using instrumentation to observe, collect data, and measure parameters of communication in accordance with the principles of evidence-based practice;
• selecting, fitting, and establishing effective use of prosthetic/adaptive devices for communication.

The purpose of the audiologic assessment is to

• assess the integrity of the auditory system in each ear,
• measure hearing sensitivities across frequencies,
• determine the type of hearing loss,
• establish a baseline for future monitoring,
• provide ear-specific information needed to initiate amplification device fitting,
• assess the impact of the degree of hearing loss on functionality and/or quality of life.

Audiologic assessment typically includes

• case history;
• otoscopy;
• acoustic immittance procedures, including tympanometry, static immittance, and acoustic reflex measures;
• otoacoustic emissions (OAEs) screening;
• pure tone audiometry-
  • air conduction,
  • bone conduction;
• speech audiometry-
  • speech reception thresholds or speech detection/awareness thresholds,
  • word recognition measures.

Additional tests may include

• self-assessments, including communication inventories and needs assessment inventories,
• auditory brainstem response (ABR).

Case History

Accurate diagnosis of hearing loss relies on the audiologist's interpretation of a test battery within the context of the individual's medical and/or developmental history. Case history information may indicate a need for modification of evaluation procedures. For example, the audiologist may include evaluation of the high-frequency region of the cochlea (above 4000 Hz) for an individual with a history of ototoxic drug exposure. Modification of routine assessment procedures also may be necessary to adequately evaluate individuals with multiple disabilities.

Examples of questions that might typically be included on a case history are listed below. The specific questions may vary, based on the age and circumstances of the patient.

Case history typically includes information related to

• family history of hearing loss;
• medical history, including
  • general health history;
  • history of ear infections;
  • medication use (prescriptions and/or over-the-counter medications);
  • presence of other disabilities;
  • previous hearing screening and testing results;
  • presence of pain or discharge from ears;
  • history of dizziness, balance problems, or falls;
  • presence of tinnitus;
• speech and language development;
• noise exposure, including during recreational and occupational activities;
• changes in social interaction;
• changes in academic performance;
• experience with social/emotional bullying;
• hearing history, including
  • when the difficulty with hearing was first noticed;
  • whether the onset of hearing loss was gradual or sudden;
  • types of difficulties experienced (i.e., more difficulty hearing women's, men's, or children's voices; having to frequently ask people to repeat; hearing people speak, but not understanding what is being said);
  • whether there are situations where it is more difficult to follow a conversation, such as a noisy restaurant, a theater, large groups, cars, etc.;
  • feedback from others (e.g., comments regarding speaking too loudly in conversations or turning up the volume on the television).

Case history is recorded using a standard format. See the cultural competence Practice Portal page for information regarding gathering a case history.

Otoscopy

Visual inspection of the pinna and ear canal, including otoscopy, precedes audiometric testing to rule out active pathological conditions and the potential for ear canal collapse caused by audiometric earphones. The audiologist ensures that the external auditory canal is free of excessive cerumen before testing.

Acoustic Immittance Testing

Acoustic immittance testing is useful in localizing the site of lesion for the hearing loss. Acoustic immittance testing may include tympanometry and/or acoustic reflex testing.

Tympanometry

Tympanometry is performed with a 226 Hz probe signal. Parameters of tympanograms to be investigated include

• tympanometric peak pressure,
• tympanometric width,
• static immittance,
• ear canal volume,
• tympanometric shape.

A tympanogram is a graphic representation of the relationship of acoustic impedance and air pressure of the middle ear and the mobility of the tympanic membrane. Various middle ear pathologies (otitis media, otosclerosis, and tympanic membrane perforations) yield distinctive tympanograms. Compliance is plotted vertically on the tympanogram and is measured in ml or mmho. Maximum compliance of the middle ear system occurs when the pressure in the middle ear cavity is equal to the pressure in the external auditory canal. The maximum compliance value (static acoustic admittance) occurs at the highest peak of the curve on the graph (Figure 1). Pressure is indicated on the horizontal axis of the graph and is measured in decapascals.

Figure 1. Tympanogram Showing Maximum Peak Compliance

(Duffey, 2007)

There are three main types of tympanograms: A, B, and C. In a Type A tympanogram, peak compliance occurs at or near atmospheric pressure, indicating a normal middle ear system, free of fluid or physiological anomalies that would prevent the admittance of sound from the middle ear into the cochlea. Figure 1 shows an example of a Type A tympanogram.

Type B tympanograms have no sharp peak and little or no variation in impedance over a wide sweep range. A Type B tympanogram (Figure 2) is indicative of middle ear pathology, such as fluid or infection behind the tympanic membrane. In some cases, these tympanograms are seen when there is a hole in the tympanic membrane with the difference being the ear canal volume: a larger ear canal volume indicates a perforation in the tympanic membrane.

Figure 2. Type B Tympanogram

(Duffey, 2007)

Type C tympanograms (Figure 3) are similar in shape to Type A tympanograms, but are shifted negatively on the graph, with peak compliance significantly below zero (usually less than -200), indicating negative pressure within the middle ear space. This finding is often consistent with sinus or allergy congestion or the end-stages of a cold or otitis media.

Figure 3. Type C Tympanogram

(Duffey, 2007)

Acoustic Reflexes

Ipsilateral and contralateral acoustic reflexes are performed to assess the integrity of the acoustic reflex pathway. Acoustic reflex thresholds (ARTs) are measured at 500, 1000, and 2000 Hz. Testing at 4000 Hz is not recommended, because many people with normal hearing have elevated reflexes at this frequency (Gelfand, 1984; Silman & Silverman, 1991).

Normal ARTs range from about 85 to 100 dB SPL for pure tone stimuli (Gelfand, 1984).

• Conductive pathology: acoustic reflexes are
  • typically absent in the probe ear, because the pathology prevents the ability to monitor changes in immittance at the probe tip, or
  • typically elevated in the stimulus ear, because the stimulus reaching the cochlea is reduced by the amount of the air-bone gap.
• Sensorineural pathology: ARTs are dependent on hearing sensitivity.
• Retrocochlear pathology: pathology is associated with ARTs that are either elevated above what they would have been in sensorineural hearing loss (above the 90th percentile) or absent.

Reflex Decay

Acoustic reflex decay is the reduction in the magnitude of the acoustic reflex during a prolonged stimulus. Reflex decay is measured at 500 and 1000 Hz only, because rapid adaptation is common at higher stimulus frequencies. Reflex decay is typically measured contralaterally. Reflex decay is abnormal if the reflex is reduced more than 50% over the first 10 seconds. Abnormal reflex decay is associated with retrocochlear pathologies.

Otoacoustic Emmissions

Otoacoustic emissions (OAEs) are used to assess cochlear function and are useful in differential diagnosis. OAEs are best measured in a quiet environment (e.g., in a quiet room with no one speaking and minimal background noise). A snug probe fit is essential for valid and reliable recordings. Ears are tested one at a time. Acceptable OAE protocols include

• Transient Evoked Otoacoustic Emission (TEOAE): One level (e.g., 80 dB pSPL) click stimulus. Normal distributions for this condition for normal hearing are documented in the literature (Hussain, Gorga, Neely, Keefe, & Peters, 1998).
• Distortion Product Otoacoustic Emission (DPOAE): One level of L₁ and L₂ 65/55 dB SPL for at least four frequencies. Normal distributions for this condition for normal hearing are documented in the literature (Gorga et al., 1997).

Pure Tone Audiometry

General Considerations

The audiologist is responsible for ensuring regulatory compliance prior to conducting testing. Regulatory requirements identify specifics and required documentation. Familiarization to the test tone before threshold measurement is not recommended.

If unilateral hearing loss is suspected, the audiologist uses appropriate masking, rules out testing errors, and verifies proper function of the audiometer and transducers. In instances of atypical threshold responses, such as identical thresholds in both ears or unusual configurations, the audiologist considers reinstruction and/or retest to verify threshold accuracy and verifies proper function of the audiometer and transducers.

Air-Conduction Measures

Stimuli: Continuous, warble or pulsed tone signals are used. Pulsed tones have been shown to increase a test participant's awareness of the stimuli (Burk & Wiley, 2004).

Transducer: Earphones (supra-aural, circumaural, and insert) used for pure tone audiometry shall be appropriate to the test technique used. Transducers are matched to the audiometer and should not be interchanged without recalibration. Supra-aural and insert earphones are appropriate for air-conduction threshold measurements from 125 Hz through 8000 Hz, while circumaural earphones are used for extended high-frequency measurements within their respective frequency and intensity response ranges.

• Diagnostic testing: Thresholds are typically assessed at 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz, except when a low-frequency hearing loss exists or is suspected, in which case the hearing threshold at 125 Hz is also measured. Inclusion of 3000 Hz and 6000 Hz frequencies in routine testing of air-conduction thresholds may provide the audiologist with a more complete profile of the patient's hearing status for prevention and diagnostic purposes (Fausti et al., 1999; Holmes, Niskar, Kieszak, Rubin, & Brody, 2004; Humes, Joellenbeck, & Durch, 2005).

When abrupt differences of 20 dB or more occur between adjacent octave frequencies, additional frequencies may be added at the discretion of the tester (ANSI, 2009).

Order: The better ear, when known, is tested first. Initial test frequency is typically 1000 Hz. Following the initial test frequency, the audiologist tests at, in order, 2000, 3000, 4000, 6000, and 8000 Hz, followed by a retest of 1000 Hz before testing at 500, 250, and 125 Hz. A retest at 1000 Hz is not necessary when testing the second ear. Presentation order of frequencies does not significantly influence test results (ANSI, 2009). The above order is an arbitrary choice that will ensure consistency of approach and minimize risk of omissions.

Masking: Air-conduction pure tone audiometry can be confounded by crossover or contralateralization of the signal, which occurs when a signal presented to one ear, if it is of sufficient magnitude, is perceived by the other ear. Interaural attenuation is the reduction in sound energy of a signal as it is transmitted by bone conduction from one side of the head to the opposite ear. Interaural attenuation for air conduction can range between 40 and 80 dB. Masking should be used if the difference in air conduction in the test ear and bone conduction in the non-test ear is 40 dB or greater. The type and level of masking are noted on the form on which the test results are recorded.

Bone-Conduction Measures

Transducers: Bone vibrators are used for bone-conducted threshold measurements for frequencies within their respective frequency response ranges and must meet the specification of Mechanical Coupler for Measurement of Bone Vibrators (ANSI, 2002). Standard bone-conduction vibrator placement should allow mastoid or forehead placement with proper force applied (Dirks, 1964). The test ear should never be covered or occluded for standard bone-conduction measurements. The contralateral ear will be covered or occluded when masking is being used.

Frequency: Thresholds are measured at octave intervals from 250 to 4000 Hz and at 3000 Hz. When testing is performed for bone conduction at 250 Hz and 500 Hz and thresholds are obtained in the 35 and 55 dB HL range, there is a high probability that the responses were a result of tactile rather than auditory stimulation (Roeser, Valente, & Hosford-Dunn, 2007). Suspected vibrotactile responses are noted on the audiogram form. Higher frequencies may be tested if the transducer has sufficient frequency-response characteristics.

Order: The initial frequency used for testing should be 1000 Hz. After the initial test frequency, the audiologist should test at 2000, 3000, and 4000 Hz, followed by a retest at 1000 Hz before testing at 500 and 250 Hz.

Masking: Typically, if the unmasked bone-conduction threshold is 10 dB or greater than the air-conduction threshold at that frequency in either ear, masking is used. Because the threshold values on which the calibration of bone vibrators is based were measured with masking noise in the contralateral ear, the audiologist may prefer to always use masking in the testing procedure. The type and magnitude of the masking sound should be noted on the form on which the test results are recorded.

Modifications of Pure Tone-Audiometry

The chart below offers potential test modifications for issues encountered during pure tone audiometry. The modifications are not intended to be comprehensive in scope or ideal for all situations. Sound clinical judgment is always paramount.

Speech Audiometry

Speech audiometry includes speech awareness/detection thresholds, speech recognition thresholds, word recognition testing, and sensitized speech testing (filtered, compressed, speech in noise, etc.) and is used to evaluate hearing sensitivity and speech perception ability and for site-of-lesion testing.

Speech Thresholds

A speech threshold test quantifies an individual's hearing threshold level for speech. Agreement between the speech threshold and the PTA should be -/+7 dB. The option to substitute a Fletcher average (the two best frequencies) is appropriate when the hearing loss is sloping (>15 dB/octave) in configuration. Clinically, the primary purpose of a speech threshold test is to serve as a validity check for the pure tone audiogram.

Speech Threshold Definitions

Speech Recognition Threshold (SRT). The speech recognition threshold is the minimum hearing level for speech (ANSI, 2010) at which an individual can recognize 50% of the speech material. Speech recognition thresholds are achieved in each ear. The term speech recognition threshold is synonymous with speech reception threshold. Spondaic words are the usual and recommended test material for the speech recognition threshold. Other test materials can be used. If so, then the test material should be noted in recording and reporting the results.

Speech Detection Threshold (SDT)/Speech Awareness Threshold (SAT). The SDT/SAT is the minimum hearing level for speech at which an individual can just detect the presence of speech material 50% of the time. The listener does not have to identify the material as speech, but must indicate awareness of the presence of speech sounds. The material used to obtain a speech detection threshold should be noted in recording and reporting the results.

General Considerations for Clinical Determination of the Speech Threshold

When circumstances or individual capabilities prevent determination of a speech recognition threshold (SRT), the speech detection threshold (SDT), sometimes referred to as speech awareness threshold, may be determined instead. The SDT will occur at a lower level than the SRT, because the SDT depends on audibility alone, whereas the SRT requires that a patient both hear and identify the speech signal. Threshold of detection can be expected to be approximately 5 to 10 dB better than threshold of recognition.

The type of speech material is not as critical for this measure, because it reflects detection and not recognition. Some common materials are speech babble, running speech, or familiar words. Nevertheless, specification of the type of material helps to ensure test-retest reliability and may be useful information for future hearing evaluations.

The usual response mode for obtaining the speech recognition threshold is repetition of the stimulus item. For patients for whom it is not possible to obtain verbal responses, alternative response modes are needed. Many alternatives are acceptable but must convey recognition of test items from a closed set of choices. For example, response modes can take the form of picture pointing, signing, or visual scanning. In addition, if a picture-pointing task is used for obtaining the speech recognition threshold, then the clinician should be cautious in choosing the number of response items. Too few items increase the probability of chance performance, and too many items may be distracting and increase response time (e.g., a number between 8 and 12 words is usually appropriate). The audiologist considers behavioral, cognitive, and language issues that may impact a patient's testing results.

For assessing the speech detection threshold, a number of response modes can be used to convey signal detection. Usually, these response modes are nonverbal. Whenever a response mode other than repetition of a spondaic word is used, it should be specified in recording and reporting the results.

The basic procedure for determining speech recognition thresholds consists of instructions, familiarization, a single series of descending threshold determinations, and calculation of threshold hearing level.

Either a recorded or a monitored live voice technique can be used to obtain the speech threshold. Recorded presentation of the test material is the preferred procedure. When monitored live voice is used, it should be noted with the test results.

Techniques for establishing an SRT include:

Technique A (after Downs & Minard, 1996)

• Familiarize the patient with the spondees.
• Present one spondee at the lowest attenuator setting (or 30 dB below an SRT established during a previous evaluation). Ascend in 10 dB steps, presenting one word at each level, until the patient responds correctly.
• Descend 15 dB.
• Present up to five spondees until (a) the patient misses three spondees, after which you should ascend 5 dB and try again, or (b) the patient first repeats two spondees correctly. This level is the SRT.

Technique B (after Huff & Nerbonne, 1982)

• Familiarize the patient with the spondees.
• Present one spondee at a level approximately 30 dB above estimated threshold. If the patient does not respond correctly, increase the intensity by 20 dB. If the patient responds correctly, decrease the level by 10 dB.
• Continue to present one word until the patient does not respond correctly. At this level, present up to five words. If the patient identifies fewer than three words, increase the level by 5 dB. If the patient identifies three words, decrease the level by 5 dB.
• Threshold is the lowest intensity level at which three out of five words are identified correctly (Stach, 2010).

Masking: When the obtained speech recognition threshold (or speech detection threshold) of one ear exceeds the apparent speech recognition threshold (or speech detection threshold) or a pure tone bone conduction threshold at either 500, 1000, 2000, or 4000 Hz in the contralateral ear by 40 dB or more, masking should be applied to the non-test ear. The appropriate masker for a speech stimulus must have a wideband spectrum (e.g., white noise or speech-spectrum noise). The level of effective masking used should be sufficient to eliminate reception by the non-test ear without causing overmasking and should be recorded on the same form as that used to record audiometric results.

Word Recognition

Word recognition scores are obtained for each ear using phonetically balanced (PB) monosyllabic words and are expressed as a percent correct. There are several word lists available.

Testing may be terminated after 10 words, if no errors occur, or after 25 words, if there are no more than four errors. Otherwise, the full 50-item list is administered (Runge & Hosford-Dunn, 1985).

Masking: Masking is used for word recognition testing when the presentation level in the test ear exceeds the best bone conduction threshold in any of the speech frequencies for the non-test ear (500, 1000, and 2000 Hz) by 35 dB or more (Roeser et al., 2007).

Either a recorded or a monitored live voice technique can be used to obtain the word recognition score. Recorded presentation of the test material is the preferred procedure, as it standardizes the composition and presentation of the test list, allows for better control of the intensity of the test items, and ensures that the speech pattern of the recorded talker will be consistent for each client. When monitored live voice is used, it should be noted with the test results.

Specific considerations are given when evaluating the speech recognition skills of non-English and limited English proficient (LEP) speakers. Monolingual audiologists may not be able to appropriately administer and monitor tests developed in other languages, whether presented in live voice or pre-recorded. Reducing the test set size by including only familiar words may result in inaccurate threshold measurements. Alternative measures of speech recognition have been developed, such as using paired digits as stimuli. This measure has been found to accurately evaluate the hearing threshold for speech in non-native English speaking adults and to closely match the pure tone average (PTA) threshold. The services of a trained interpreter/translator may be needed to obtain the most accurate word recognition scores. However, it is not appropriate to simply translate English materials. Test materials must reflect the phonetic balance of the patient's language.

Self-Assessments

A number of self-assessments are available to measure the level of disability or handicap caused by the hearing loss in a patient's everyday life and provide an individualized assessment of specific situations that cause communication difficulty to the patient. Measuring the extent to which a hearing loss is limiting or restrictive provides the audiologist with additional information about the patient's communication needs and motivation and serves as an outcomes measure or as a baseline assessment against which to compare the eventual benefits gained from hearing aid amplification. See self-test for hearing loss.

Auditory Brainstem Response

Auditory brainstem response (ABR) testing is used mainly to diagnose hearing loss in difficult-to-test patients and for differential diagnosis of cochlear hearing loss versus retrocochlear hearing loss, specifically tumors of cranial nerve VIII. Auditory evoked potentials, originating from cranial nerve VIII and auditory brainstem structures, consist of five to seven identifiable peaks that represent neural function of the auditory pathways and nuclei. The ABR is a sensitive indicator of functional disorders of the VIIIth nerve and lower auditory brainstem and is often the first test of choice if a disorder is suspected.

The ABR component waves, especially Waves I, III, and V, are easily recordable in many cases and are very reliable in terms of their latency. Although absolute numbers will vary across clinics, the latencies are relatively stable across individuals. The I-V interpeak interval in most adults is approximately 4 msec, and the standard deviation of this interval is about 0.2 msec. Thus, 95% of the adult population have I-V interpeak intervals of 4.4 or less. If the I-V interval exceeds this amount, it can be considered abnormal (Stach, 2010).

Click stimuli at a high level (e.g., 80-90 dB nHL) is adequate in most situations to identify Waves I, III, and V. If no response is obtained at the maximum output level, the audiologist obtains one run of rarefaction clicks and one of condensation clicks to distinguish between cochlear and neural dysfunction. A catch trial (i.e., signal running but not delivered to the ear) can rule out a stimulus artifact that may be misinterpreted as the cochlear microphonic (CM).

Latency Measures

Measurements that are used include

• comparison of Wave V latency with distribution of normal values;
• interaural comparison of peak latencies
  • If the difference in value of the Wave V peak latency between ears is greater than .2 ms, test is positive for a tumor (Selters & Brackmann, 1977);
• comparison of interpeak latencies (I-V and I-III) with distribution of normal values;
• interaural comparison of interpeak delays.

Note: Cochlear pathologies are typically associated with a delay of Wave I.

Amplitude Measures

Measurements that are used include

• comparison of Wave V amplitude with distribution of normal values,
• interaural Wave V amplitude comparison,
• comparison of Wave V/I amplitude ratio with distribution of normal values,
• interaural Wave V/I amplitude ratio.

Threshold Testing

When behavioral audiometric tests are judged to be unreliable (i.e., non-organic hearing loss), ear-specific thresholds cannot be obtained, or results are inconclusive regarding type, degree, or configuration of hearing levels, threshold testing-such as ABR, bone conduction, or ASSR-may be used as part of the assessment process to predict hearing thresholds.

Frequency-Specific ABR

Predicting hearing sensitivity using ABR involves determining the lowest intensity level at which an auditory evoked potential can be identified. Click or tone-burst stimuli are presented at an intensity level that evokes a response. The level is then lowered, and the response is tracked until an intensity is reached at which the response is no longer observable. This level corresponds closely to behavioral threshold.

Stimuli: Frequency-specific stimuli are tone bursts of low, mid, and high frequencies.

Transducer: A complete audiologic evaluation includes both an air-conduction and bone-conduction ABR, when indicated. Insert earphones are recommended, unless contraindicated, for air-conduction testing.

Bone Conduction

Bone-conduction thresholds are established in a manner similar to air-conduction thresholds, but with a different transducer. A bone vibrator is used to generate vibrations of the skull and stimulate the cochlea directly. In theory, thresholds by bone conduction reflect function of the cochlea, regardless of the status of the outer or middle ears.

Note: Responses are typically attempted down to 20 dB nHL in at least 10 dB steps.

ASSR

The auditory steady-state response (ASSR) is an auditory evoked potential, elicited with modulated tones that can be used to predict hearing sensitivity in patients of all ages (Dimitrijevic et al., 2002; Rance & Rickards, 2002). The response itself is an evoked neurological potential that follows the envelope of a complex stimulus. It is evoked by the periodic modulation of a tone. The neural response is a brain potential that closely follows the time course of the modulation. The response can be detected objectively at intensity levels close to behavioral thresholds. The ASSR can yield a clinically acceptable, frequency-specific prediction of behavioral thresholds.

Stimuli: Frequency-specific stimuli are amplitude- and frequency-modulated pure tones with typical carrier frequencies of 500, 1000, 2000, and 4000 Hz.

Transducer: Insert earphones are recommended, unless contraindicated, for air-conduction testing. A bone-conduction transducer will be needed if air conduction is elevated (i.e., if air-conduction thresholds are greater than 20 dB nHL, bone-conduction testing is completed to assess the type of hearing loss).

Note: ASSR analysis is mathematically based. The specific method of analysis to define threshold is dependent on the manufacturer's statistical detection algorithm.

Equipment and Test Environment

It is essential that all audiometric equipment be calibrated, be functioning properly, and be used in an acceptable test environment to ensure accurate test results as specified in American National Standards Institute/Acoustical Society of American (ANSI/ASA) Standard s3.6-2010.

Equipment And Calibration

Equipment and transducers are to meet applicable specifications of ANSI/ASA S3.6-2010 (ANSI, 2010), ANSI S3.39-1987 (ANSI, 1987), and manufacturer specifications and be appropriate to the test technique being used. In addition, exhaustive electroacoustic calibrations are to be performed annually using instrumentation traceable to the National Institute of Standards and Technology; functional inspection, performance checks, and bioacoustic checks are conducted daily to verify equipment performance prior to use (ANSI, 2010).

Transducers

• Use of specific transducers may be dictated by a particular regulatory standard, such as the use of insert earphones for audiometric monitoring under the Occupational Safety and Health Administration (OSHA) hearing conservation amendment (1983). The applicable regulation should be consulted before testing to ensure compliance.
• The audiologist controls placement of the transducers on the listener.

Test Environment

Test environments should meet the specifications detailed in Maximum Permissible Ambient Noise Levels for Audiometric Test Rooms (ANSI, 2003). In addition,

• audiometric test rooms typically include visual and/or auditory warning systems connected to the building warning system (fire, civil defense) and are equipped with an emergency telephone or a panic button to signal for emergency assistance;
• mobile phones, pagers, radios, and other communication devices are silenced or turned off during the audiometric evaluation;
• the test room and audiologist's work area provide for proper control of temperature, air exchange, and humidity.

Confirmation of an acceptable test environment should be documented at least annually.

Infection Control

Adherence to universal precautions and appropriate infection control procedures should be in place. Instrumentation coming into physical contact with the patient must be cleaned and disinfected after each use. Disposable acoustically transparent earphone covers or disposable insert earphone tips are recommended, and clinician hand washing between patients should be routine (Siegel, Rhinehard, Jackson, Chiarello, & the Healthcare Infection Control Practices Advisory Committee, 2007). See OSHA standards relating to occupational exposure to bloodborne pathogens and the Centers for Disease Control and Prevention's universal precautions for preventing transmission of bloodborne infections.

Service provision for patients with hearing loss begins soon after the diagnosis is made and comprises audiologic rehabilitation, including the selection, fitting, and evaluation of technology (if amplification is selected as a treatment approach). When selecting any treatment approach, the audiologist considers and incorporates the individual's and his/her family's goals, preferences, values, beliefs, and cultural and linguistic background.

Treatment approaches include

• medical referral for evaluation;
• counseling regarding the nature of the hearing impairment and the effects of the impairment on communication and well-being;
• counseling to address specific interpersonal, psychosocial, educational, and vocational implications of hearing impairment for the patient, family members, and/or caregivers;
• counseling regarding the use of effective coping and compensatory skills to minimize the effect of the hearing impairment;
• selecting and fitting of amplification devices and assistive technologies and education regarding the use, benefits from, and adjustments to these systems;
• training in selected modalities to maximize receptive communication skills and performance environments relevant to the patient;
• periodic review of short- and long-term treatment goals and specific objectives determined from self-assessments and interactive decision making;
• regularly scheduled outcomes measures to identify need for modifications to the treatment plan;
• follow-up to monitor treatment benefit and outcomes;
• involvement of family members and/or caregivers in the rehabilitative process;
• referrals to speech-language pathologists for individuals whose speech and/or voice production may be affected by their hearing impairment;
• referrals to other professionals as necessary.

Individual Practice Portal pages on amplification, cochlear implants, audiologic rehabilitation, and aural rehabilitation are being developed; links will be provided in the future.

Hearing Assistive Technology Systems

Hearing assistive technologies systems (HATS) include a large variety of devices designed to improve audibility in specific listening situations. HATS may be designed for use with hearing aids or cochlear implants or to be used alone and may be intended for personal use or group use. See classroom acoustics.

The American Academy of Audiology Task Force (2011) suggests several steps for the provision of HATS. While the guidelines are specific to remote microphone HATS for children, these steps may also be relevant to adults and to other forms of HATS. They include:

• evaluating the client's candidacy for HATS;
• considering the acoustics of the client's daily environments, social/emotional factors, functional abilities, and external support;
• selecting the most appropriate device;
• fitting and verifying the HATS;
• implementing and validating the HATS.

Examples of HATs include

Frequency Modulation (FM) Systems—radio waves are used to transmit sound from the source to a receiver worn by a person. FM systems are often used in large settings (e.g., classrooms, restaurants, nursing homes, theaters, places of worship, museums).

Infrared Systems—sounds are converted into infrared waves then back to sounds by the listener's infrared receiver. These systems are often used in the home with television sets, but can also be used in large settings, such as theaters or classrooms.

Induction Loop Systems—hard-wire loops are placed under floors or around walls, and sounds are converted to magnetic forces. Cochlear implants and hearings aids with telephone switches or t-coils pick up these forces and convert them to sounds.

Telephone Amplifiers—speech heard over the phone is amplified. Telephone amplifiers are useful for people who don't wear hearing aids.

Voice Carryover Telephones (VCO)—VCO telephones connect a person with hearing loss to a local relay service.

Text Telephones (TTD or TTY)—this telephone works like a typewriter and sends and receives typed messages through telephone lines.

Alerting Devices—devices that provide a signal in response to sound may use strobe lights, regular lights, or vibrating systems to alert a person with a hearing loss that a sound has occurred. Examples include

• doorbell, knock-at-the-door, or telephone alerting devices;
• fire alarm/smoke alarm devices;
• baby-crying or room-to-room sound alerting systems;
• vibrating clock alarms, paging systems, and watch alarms.

Personal Amplification Systems—systems such as streamers (Bluetooth), mini remote microphones, and apps are designed for individuals with hearing loss.

HATS system selection considerations include

• the need for, and potential benefits of, HATS as determined by the patient;
• compatibility of HATS when used in conjunction with hearing aids, cochlear implants, and other devices;
• appropriateness of the electroacoustic characteristics of HATS for the patient's hearing impairment;
• compatibility of HATS in different environments (e.g., church, home, school);
• self-reports of successful use and satisfaction with HATS.

• Roles and Responsibilities of SLPs in Schools (2010)
• School Setting Resources for Audiologists
• Resource Guide for Educational/Pediatric Audiologists

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Acknowledgements

Content for ASHA’s Practice Portal is developed through a comprehensive process that includes multiple rounds of subject matter expert input and review. ASHA extends its gratitude to the following subject matter experts who were involved in the development of the Hearing Loss: Ages 5+ page:

• Carmen Brewer, PhD, CCC-A
• Karen Farmer, MS, CCC-A
• Susan Gordon-Hickey, PhD, CCC-A
• Gail Linn, AuD, CCC-A
• Margaret McCabe, AuD, CCC-A
• Robert Moore, PhD, CCC-A
• Carrie Spangler, AuD, CCC-A

Citing Practice Portal Pages

The recommended citation for this Practice Portal page is:

American Speech-Language-Hearing Association (n.d.). Hearing Loss: Ages 5+ (Practice Portal). Retrieved month, day, year, from /Practice-Portal/Clinical-Topics/Hearing-Loss/