1. Introduction to Audiology
How to Read an Audiogram
Degrees of Hearing Loss
Types, Causes and Prevalence of Hearing Loss
Types of Tests
Today we will introduce basic audiology procedures. We will touch on the components of sound, how to read an audiogram, how the threshold of hearing is determined, the types of tests available for various age groups, the types of hearing loss you may see on an audiogram, as well as try to provide more information about just what it is we do in a soundbooth.
Most people are surprised to learn that audiologists can test hearing on essentially everyone, regardless of the level of cooperation provided. As a general rule, the less cooperation we get, the more involved the testing process, but that isn’t always the case.
We’ll discuss tried and true methods of hearing testing, including assessments in the soundfield, as well as the latest method we have to assess function of outer hair cells, the Otoacoustic Emissions Test.
We will view examples of normal hearing, as well as different configurations of hearing loss. After the presentation today, it shouldn’t be difficult to comprehend an audiogram and understand what it means to the communicative ability of the patient.

2. How to Read an Audiogram
Terminology Used
Hertz (Hz) is used to describe frequency or pitch, cycles per second
Decibel (dB) is the unit that describes the intensity, or loudness, of the sound
Hearing is measured in decibels, and recorded across the frequency spectrum. Frequencies are measured in Hertz, sometimes thought of as cycles per second. The audiogram reads left to right, from low pitch or frequency to high pitch or frequency.
The unit of loudness is called the decibel, and is read on the graph from top to bottom. The softest, or least intense, sounds are charted near the top of the graph, and the louder sounds are represented by the larger numbers toward the bottom of the graph.
Let’s now look at the symbols on the graph. These symbols are used around the world. An audiogram performed in Spain or Germany looks very similar to one performed in Canada or America.

3. Audiometric Symbols(1)
Look for the Key on Chart
Air
Right
Left
Bone
Forehead
Every audiogram should have a legend. It is possible to interpret the results based on the key to the symbols, found on the chart. Some may be printed in color, while some are black and white. Historically, the color RED has been used to indicate responses from the RIGHT ear. Many people can remember the phrase “Red Round Right” to help understand results.
Results from soundfield testing are generally indicated by a large “s” and indicate the frequency of the test signal…recommended stimuli are Warbled Tones or Narrow Bands of Noise. S
Soundfield

4. Masked Audiometric Symbols(1)
Masked Left Ear Masked Right Ear
Air
Bone
Masking is performed during air conduction tests when there is a given difference between ears. There is a chance the sound directed to the poorer ear might be heard by the better ear. Masking during bone conduction allows responses to be obtained from each ear. With young patients this can be challenging, and the success is often dependent on the developmental age and attention level of the child.
Masking noises during pure tone tests are narrow bands of noise centered around the test frequency, and during speech tests, the noise is a wide band of noise which incorporates the speech frequencies.
The idea behind masking is to keep one ear “busy” while testing the opposite side

5. Audiometric Symbols Universally Used
Pure Tone Air Conduction
Pure Tone Bone Conduction
May be Masked or Unmasked
Tests in Soundfield (Narrow Band Noises, Warble Tones, or Speech)
May obtain responses to Speech via Air and/or Bone Conduction pathways
Sound can either be conducted via airwaves through the ear canal, middle ear and into the inner ear (actually, the energy changes to mechanical in the middle ear, then to hydraulic)…or we can stimulate the inner ear mechanism directly by use of bone conducted signals.
We can mask the opposite ear, to isolate the responses from the test ear. In essence, we are keeping the non-test ear out of the picture while we determine the hearing ability of the test ear.
Testing in soundfield is performed when the patient will not, or cannot, tolerate placement of headphones It can also be used to determine the functional improvement of a person using hearing aids.
Testing with speech stimuli can be performed via air or bone conduction pathways.

6. Normal Hearing(2)
This is a good example of normal hearing in both ears. You will notice that tests via air and bone conduction were performed. The key to the symbols used is on the right side in this example.
A frequent area of confusion occurs relative to the “zero line”. Zero decibel does not mean the absence of sound, but rather the softest sound that can be detected by the normal adult human ear at that frequency. Studies to determine this were begun in the 1930s, and have been used to determine the ANSI and ISO current standards for calibration of audiometric equipment.

7. Determine Hearing Level
Establish Hearing Threshold Level
(HTL or simply HL)
What is threshold?
With earphones or via bone, softest sound detected 50% of time
In the soundfield, tests reveal response of better ear
To determine hearing level we must determine the threshold of hearing. Conventionally defined as 50% of tones or words heard, and that concept is a bit tricky. It is important to understand the threshold of hearing means the ability to BARELY hear the sound, a concept difficult to understand by many adults, let alone children!
Testing can be accomplished under earphones or in soundfield. Stimuli used are pure tones, words, narrow bands of noise, and warbled tones. A test performed in soundfield reveal how the BETTER ear is performing, as both ears participate in soundfield testing.
Speech Reception Threshold (SRT) is softest level possible to hear closed set of bi-syllabic words
Thresholds are measured in decibels (dB) at various frequencies, reported in Hertz

8. Speech Reception Threshold
Softest level of speech that can be understood 50% of the time
Bi-syllabic vocabulary may include words tailored for pediatric patients
Ear specific, if earphones used
Obtained via air and/or bone conduction
Correlates closely with pure tone average at 500 Hz, 1000 Hz and 2000 Hz
Provides estimate of hearing for speech
With some children, the SRT is the first and only test that can be obtained. The SRT gives a snapshot of the child’s hearing, and can serve as a basis to decide which tests to perform next.
The SRT is performed with adults as an internal check or cross-check for the pure tone results. We expect an SRT to agree within 5dB of the Pure Tone Average (PTA) of 500 Hz, 1000 Hz, 2000 Hz.

9. Determine Amount of Loss (3)
Hearing impairment is documented unilateral or bilateral sensorineural, mixed, or conductive hearing levels greater than 20dB HL
The term impairment is considered “any loss or abnormality of psychological or physiological function. It implies that some functional aspect of an organ, system or mechanism is outside a normal range.” (3)
This point is stressed because various audiologists define Normal Hearing differently…either 0-25dB HL or 0-20dB HL. Rather than using absolute numbers, it is likely best that we get in the habit of thinking of the true handicap to the individual that is imposed (or not) by the hearing thresholds on the audiogram, and consider the function of that individual in school, work or society as we recommend habilitative or rehabilitative measures.

10. Determine Amount of Loss
Minimal, or mild, hearing loss is from
25dB - 40dB HL(4,5)
Moderate loss is from 40dB - 70dB HL
Severe loss is from
70dB - 90dB HL
Profound loss is greater than 90dB HL
Historically, 0-25dB HL was considered normal hearing, and many audiologists still refer to that range as normal. In fact, you’ll see it depicted that way on the following slide. A more conservative approach is to think of 0-20dB HL as being in the normal range.
Traditionally termed mild or minimal hearing loss, 25dB to 40dB HL, has been shown to have significant impact on the communicative and educational development of young children. Tharpe and Bess point out that while otitis media is considered a common childhood ailment, there exists mounting evidence that OM is not always benign and may negatively contribute to difficulties by the child, both in educational and social settings. Studies show some children with very mild bilateral or unilateral hearing loss demonstrate problems in communicative development, social and/or emotional function. (4)
(Continued on next slide)

11. Determine Amount of Loss
Minimal, or mild, hearing loss is from
25dB - 40dB HL(4,5)
Moderate loss is from 40dB - 70dB HL
Severe loss is from
70dB - 90dB HL
Profound loss is greater than 90dB HL
Likewise, many adults complain of difficulty in hearing or understanding when a so-called minimal hearing loss is present. Adults have been shown to seek hearing aids to deal with what used to be thought of as borderline hearing problems. Drs. Martin and Champlin published a paper in the Journal of the American Academy of Audiology which clearly describes why we call normal what we do, and how our traditional description of normal may not be appropriate, after all.(5)

12. Determine Amount of Loss
From bass to treble, or low to high pitch
From
faint to
intense, or
soft
loud
This slide depicts traditional ranges of hearing impairment. Most audiologists would agree on these ranges, with the exception of normal, as just explained.
(Note to speaker: Slide taken from graphic in Audiologists’ Desk Reference, Vol I, which is reference #12)

13. Types of Hearing Loss Conductive Sensorineural Mixed
Bone Conduction better than Air Conduction
Sensorineural
Bone Conduction equal to Air Conduction
Mixed
Some amount of Air and Bone Conduction loss
Conductive hearing problems may arise from otitis media, otosclerosis, tympanosclerosis, disarticulated ossicles, perforated tympanic membranes, retracted tympanic membranes, impacted cerumen; essentially any problem that prevents the efficient transmission of energy to the inner ear.
Sensorineural hearing problems, if listed in detail, could go on for pages! The most commonly thought of include genetic or familial causes, presbycusis or normal aging, hazardous noise exposure, barotrauma, ototoxic medications, Meniere’s disease, auto-immune disorder…we literally could name these for hours.
A mixed hearing loss contains some component of conductive AND sensorineural loss.

14. Prevalence of Hearing Loss
Prevalence data vary by study and by age range, but hearing loss is more prevalent than any other condition(5)
6:1000 infants(6)
25-40% > 65 years(7)
70-80% > 80 years(7)
There is no easy way to report numbers…epidemiological studies generally report on a given age range, or a given type of hearing loss. It has been reported that more hearing loss is present in the population than all other serious diseases combined (cancers, heart disease, HIV)…and that most of these cases go untreated and undiagnosed. “Hearing loss is the most prevalent health problem in North America and has a pervasive impact on almost every aspect of an individual’s life”…(15)
The effect of the impact of the hearing loss is dependent upon age at onset, degree of loss and age of diagnosis.

15. Causes of Hearing Loss
This forum doesn’t allow adequate discussion of this topic(8)
Presbyacusis (aging) is #1 cause of hearing loss(7)
Hazardous noise exposure is #2
Just a few other causes include genetics, teratogens, otitis media, idiopathic hearing loss, fistula, congenital anomaly, prenatal or perinatal exposures (syphilis, CMV, rubella), syndromes, head injury, among hundreds of others!
Only one type of hearing loss is preventable
AVOID NOISE Hazardous noise damages hearing
12.5% of children aged 6-19 have some amount of noise induced hearing loss(9)
This lesson is not intended to provide a broad exposure to causes of hearing loss. However, it should be noted that aging and noise exposure account for most hearing loss in all patients seen. To give a glimpse of how large this topic is, more than one hundred different causes exist which are believed to trigger sudden idiopathic sensorineural hearing loss (8)
EDUCATION is the key to preventing one of the leading forms of hearing loss, overexposure to hazardous noise! If exposed to noises greater than 85dB, use hearing protection. A quick and easy rule of thumb is this “if you have to shout to be heard at 3 feet (arm’s length) chances are that is hazardous noise, and ear protection should be used”. Hearing protection can be purchased at drugstores, sporting goods stores, while custom-made is available from an audiologist. Talk to everybody about preventing hearing loss by avoiding overexposure to noise!!

16. Tests Frequently Used Speech Reception Threshold Tests in Soundfield
Air Conduction
Bone Conduction
Immittance or Tympanometry
Various Screening Tests
OAE, AABR, Hand-held audiometer
The upcoming slides will explain various tests that can be used by an audiologist to determine the status of the hearing.

17. Tests in the Soundfield
Test infants as young as 6 months
Assess Localization Skills(10)
Assess Auditory Ability(11)
VRA
COR
TROCA
VROCA
BOA
A variety of tests can be used with infants and young children in the soundfield. Some of the most popular include:
VRA=Visual Reinforcement Audiometry
COR=Conditioned Observed Responses
TROCA=Tangibly Reinforced Operant Conditioning Audiometry
VROCA=Visually Reinforced Operant Conditioning Audiometry
BOA=Behavioral Observation Audiometry
Some of the most basic and simple tests we do can provide a wealth of information about auditory development of the young child. Results are obtained in a play type environment, can utilize motorized toys or a remote controlled reward mechanism to condition the child to respond to the sound.
We are not able to capitalize on the localization response for auditory testing until infants are approximately 6 months of age. (13)
The ability to localize assesses the integration of the hearing from each ear. This is truly valuable information and can be obtained in the soundfield.

18. More Soundfield Tests(12)
Tests may be performed while patients wear hearing aids to determine word recognition in quiet or noisy backgrounds
Tests may be useful to determine amount of noise reduction provided by Hearing Protection Devices (HPD)
Estimation only, not formal assessment
Other tests that may be performed include measured functional improvement with hearing aids, or estimation of noise reduction from hearing protection devices.

19. Tests Via Air Conduction
May be as simple as a tuning fork
Most precise is with earphones
Audiologists can obtain results with earphones in children as young as 6 months
With children, thresholds obtained at a high frequency in each ear, a low frequency in each ear, then additional frequencies as attention permits
Goal is to obtain as much information as quickly as possible, short attention of child limiting factor
Several different types of stimuli may be used to attract and keep the attention of the child. Warble tones, narrow bands of noise and speech can be routed routed into the soundfield speakers via the microphone/speaker set up. These tests can be used to determine unaided hearing ability, as well as responses with hearing aids.

20. What is Conditioned Play Audiometry? (11)
Term covers a lot of ground!
Tactics used to engage the child to respond to a sound stimulus by putting block in bucket, placing peg in board, clapping their hands, etc
Maintains the interest, seems like fun, allows more information to be obtained
A special type of audiometry that can be quite successful is termed play audiometry. A child is taught to play a simple game which assists in the determination of the hearing ability. This technique is useful and beneficial for children who might otherwise be considered too young or too active to test via conventional methods. Generally this works for children aged 2 to 2 1/2 years and over.

21. Tests Via Bone Conduction
Obtain speech awareness and/or speech reception threshold, pure tone thresholds
Vital to determine middle ear status
Infants as young as 6 months can be tested behaviorally, even younger if assessment involves physiologic tests (evoked potentials)
Bone conduction tests can be carried out in the soundbooth, or with evoked potential measures, for example auditory brainstem response (ABR).
Tests using bone conducted pure tones are accomplished to assess cochlear function, and as one way to determine middle ear status. These tests can be performed with conditioned play audiometry, or more conventional methods of pushing a button or raising the hand in response to the sound.

22. Tympanometry/Immittance Measures(13)
Tympanometry provides objective results to determine status of middle ear
Acoustic reflexes are part of the test, add diagnostic information
May be obtained ipsilaterally and/or contralaterally
A(d) A
A(s) B C
Regardless of the age of the patient, many audiologists begin each evaluation with this simple, quick and effective test.
A Tympanogram is a visual representation of reflected sound waves which allows evaluation of the movement of the tympanic membrane and middle ear system.
The Acoustic Reflex occurs when the stapedial muscle contracts in response to a loud acoustic stimulation. The muscle, attached to the stapes footplate, causes the footplate to become less mobile, limiting the movement of the ossicles. Information obtained from this simple test can aid in identification of conductive hearing loss, sensorineural hearing loss, retrocochlear lesions, facial nerve disorders, and middle ear disorders.(13)

23. Immittance Tests(12)
Five classifications of results, referred to as Modified Jerger Classification System
Type A(d), A, A(s), B and C
A(d) A
Here is a graph with the five types of tympanogram results.
Type A(d) is consistent with disarticulated ossicles, overly compliant middle ear system, or monomeric tympanic membrane,
Type A is consistent with normal pressure of
(-100 mmH20 to +100 mm H20),
Type A(s) is consistent with stiffened middle ear system (may be seen with scarred TM or otosclerosis),
Type B is consistent with serous effusion,
Type C is consistent with retracted Tympanic Membrane and is commonly referred to as negative middle ear pressure. This is often seen with Eustachian tube dysfunction.
A(s) B C
-400
-200
+200

24. Otoacoustic Emissions(14)
Evoked OAE (EOAE) are sounds that come out of the cochlea upon stimulation
Spontaneous emissions (SOAE) are found in 60% of ears, 2:1 females to males
OAEs should not be confused with TINNITUS
EOAE indicate movement of Outer Hair Cells
Corresponds to thresholds <40dB HL
Presently used to screen newborns, monitor patients on ototoxic medication
Shows potential as tool to monitor noise exposure damage in cochlea
A thorough discussion of Otoacoustic Emissions could take several hours. A complete explanation is obviously beyond the scope of today’s discussion. The OAE are sounds that come out of the cochlea either spontaneously or in response to a stimulation.
It has been shown that 60% of normal ears have spontaneous emissions, and this is more than twice as likely to occur in females than in males.
The presence of Evoked OAE correlates with auditory thresholds that are better than 40dB HL.
This finding has made the Evoked OAE test a valuable screening in the newborn nursery, and shows promise in monitoring ototoxicity in patients. Evidence also indicates there may be a use for Evoked OAE to monitor cochlear function in noise exposed workers.

25. Audiology Screening Tests(3, 15)
Several screening applications exist that are totally microprocessor driven and are applicable for use in a newborn nursery or physician’s office
OAE - Otoacoustic Emissions (Transient Evoked or Distortion Product Evoked)
AABR - Automatic Auditory Brainstem Response
Hand-held audiometer, presents sounds across frequencies, patient indicates number detected
Provide “Pass” or “Refer” results
Screening equipment has been designed to be used by non-audiology staff. More and more states are requiring Universal Newborn Hearing Screen prior to age 6 months, and many communities are testing infants before they first go home from the hospital. If a screen is not passed, whether OAE or AABR, further audiological tests to determine degree and configuration of the hearing loss will then be performed. This forum does not address these methods fully, but mention is made to expose the audience to the existence of such equipment and methods.

26. Results Reveal the Story(15)
Child/Family History
Speech Reception Threshold (SRT)
Soundfield
Tympanogram
Air Conduction
Bone Conduction
Otoacoustic Emissions
Evoked Potentials
Test battery may be accomplished over several visits
Results may fluctuate over time, check for history of serous effusion in children
The Joint Committee on Infant Hearing Year 2000 Position Statement recommends that audiologic evaluation to confirm the existence of a hearing loss in infants must include physiologic measures and developmentally appropriate behavioral techniques. Adequate information cannot be obtained from a single test alone, but rather must be accumulated from a battery of tests which provide a cross-check of the auditory system. These tests serve three functions: 1) to assess the integrity of the auditory system 2) to estimate hearing sensitivity, and 3) to identify all intervention options. (15)

27. Normal Hearing
This audiogram shows air conduction values obtained with earphones at pure tone frequencies. These test results show hearing within the normal range.

28. Low Frequency Loss
(Ask the audience whether this example shows sensorineural or conductive loss?)
Since only air conduction values are noted, there is not not enough information to determine the type of hearing loss.
Further testing would include bone conduction, OAE and immittance, and would help pinpoint location of the problem.

29. Conductive Hearing Loss
An example of a left moderate low frequency conductive hearing loss. Hearing in the right ear is in the normal range.

30. High Frequency Sensorineural Hearing Loss
Example of high frequency sensorineural hearing loss of moderate degree.

31. Mixed Hearing Loss Left ear is within normal limits.
Right ear has a mixed loss in the low frequencies of moderate to severe degree, and a moderate high frequency sensorineural loss.

32. Some Closing Thoughts Components of Sound Audiometric Symbols
Hertz
Decibel
Audiometric Symbols
Unmasked and Masked
Determine Amount of Loss
Normal, Mild, Moderate, Severe, Profound
Types of Hearing Loss
Conductive
Sensorineural
Mixed
We certainly have covered a lot of ground today! Let’s briefly review what we discussed and address any lingering questions.
--The components of sound, both pitch and intensity, which are described on the audiogram in Hertz and decibels.
--The symbols used on the audiogram are universal, and can be interpreted via the legend on the form.
--We discussed the ranges of normal, mild, moderate, severe and profound hearing loss, as well as the three main types of peripheral hearing loss, conductive, sensorineural and mixed.

33. More Closing Thoughts Tests Used SRT Soundfield Air, Bone
Play Audiometry
Immittance
Screening audiometry, AABR, OAE
--We spent a great deal of time talking about the tests available to an audiologist. Some of those we discussed were Speech Reception Threshold to obtain an estimate of hearing for speech, tests commonly used in Soundfield include Visually Reinforced Audiometry and Behavioral Observation Audiometry.
--We also talked about play audiometry, where the child is encouraged to respond to the sound in a fun way, such as by putting pegs in a board, or blocks in a bucket.
--Immittance tests include tympanometry to show the compliance of the middle ear system, and acoustic reflexes which indicate presence or absence of the reaction by the Stapedial muscle to loud stimulation. We talked about the Otoacoustic Emissions, and noted that they reflect movement of the outer hair cells in the cochlea.
--Some tests are available in screening equipment; the AABR, OAE and handheld audiometer. The first two may be used in the newborn nursery, and the last may be used with older patients in the physician’s office.
The specialty of audiology encompasses far more than we were able to discuss today, but I hope you have been able to gain a greater understanding of the basics of this field.
Any questions?