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E. Kösemihal et al.
Table 8.1 Denitions of the
terms used in audiometric
evaluation
Name Denition
Audiometry Measurement of hearing range
and hearing sensitivity
Audiometer Name of the test equipment
Audiogram Chart with marked hearing
thresholds
lowest levels of sensitivity, which are called hearing thresholds, are plotted on an
audiogram graph. Relevant terms are listed in Table8.1.
Pure-tone audiometry involves air conduction measurement and bone conduction measurement. In the air conduction test, the stimulus is presented with either a
supra-aural or an insert earphone. For these transducers, sound travels through the
external ear canal and middle ear system to the cochlea. In the bone conduction test,
a bone oscillator (vibrator) is used as a transducer. The oscillator is placed on the
mastoid process of the temporal bone. It vibrates the bones of the skull, stimulating
the right and left cochleae directly (causing displacement of the basilar membrane),
thereby activating the auditory system bilaterally [8, 9].
For pure-tone audiometry, rst, a sound that the patient can hear comfortably
(typically 30–40dB HL for people with normal hearing) is presented. This is called
the familiarization phase. The patient is instructed to press a button on hearing this
sound (signal). According to age, the responding method can change (e.g., raising
the hand). It is important for the patient to respond to the softest sound they can
hear. If the patient responds, the intensity level is decreased by 10dB.If there is no
response, the intensity level is increased by 5dB to determine the threshold. This is
referred to as the “down−10, up-5” method. At least two correct responses from up
to three presentations during an ascending series of tone presentations are required
at the same intensity level to establish that the hearing threshold is at that intensity level.
The hearing test begins with a familiar tone, at 1000 Hz (mid-frequency).
However, the test may begin at lower frequencies, such as 250Hz if a severe-toprofound loss is suspected. If the test begins at 1000Hz, it will progress sequentially to higher frequencies. Lower test frequencies (500, 250, and 125Hz) are then
measured. The rst frequency measured may be reevaluated to ensure patient consistency. For behavioral audiometry, the audiologist starts with measures of the air
conduction thresholds for the right and left ears, followed by bone conduction puretone audiometry. The same procedure is used to determine thresholds [9].
Hearing thresholds are plotted on an audiogram. This graph represents the range
of −10 to 120dB HL intensity levels on the vertical axis and the frequency range of
125–8000Hz on the horizontal axis (Fig. 8.1a). Three pieces of information are
used to dene the hearing level obtained after the test. These are the degree, type,
and conguration of hearing loss.
A conguration is described as a at, curved, rising, sloping, cookie bite, or corner audiogram. A at audiogram shows thresholds within 20dB at all frequencies
tested. A sloping audiogram is characterized by thresholds worsening by 20dB or
more from low to high frequencies. In a rising audiogram, hearing thresholds are
a
b
8 Behavioral andElectrophysiological Tests inAudiology
129
Fig. 8.1 (a) An example of an audiogram showing mild-to-severe hearing loss. The speech banana
includes the frequencies and intensities of speech sounds that individuals can hear. (b) Examples
of audiometric congurations that vary according to the type of hearing loss
worse at lower frequencies, with a difference of more than 20dB relative to higher
frequencies (Fig.8.1b). A notched audiogram conguration is characterized by a
signicant decrease in one frequency compared to adjacent octave frequencies. If a
130
E. Kösemihal et al.
notch is seen at 2000Hz for bone conduction, this is called Carhart’s notch (indicative of ossicular xation). The corner-type audiogram is characterized by having a
high-intensity hearing threshold only at low frequencies and no response at high
frequencies. This is characteristic of profound hearing loss.
Audiometric congurations are essential for determining etiologies and diagnoses. Conductive hearing loss (CHL) typically has a rising conguration in middle
ear infections. Otosclerosis, another cause of CHL, is associated with a bone conduction notch at 2000Hz. A sensorineural notch in the 4000-Hz region is critical for
diagnosing noise-induced hearing loss, which may also include a drop at 3000 or
6000Hz. A presbycusis (age-related hearing loss) conguration is typically characterized by gradual, sloping sensorineural hearing loss (SNHL) at higher frequencies. An SNHL with a rising conguration may relate to the possibility of acquired
hearing loss due to Meniere’s disease, but it is also seen in some forms of hereditary
hearing loss.
The degree of hearing loss is used to classify hearing ability. Normal hearing
refers to thresholds from −10 to 25dB HL.Thresholds >25dB HL are outside the
normal range [10]. Some professional bodies, including the American Speech–
Language–Hearing Association (ASHA), more strictly dene the normal hearing
range as −10 to 15 dB HL (https://www.asha.org/public/hearing/Degree- of-
Hearing- Loss). In children, the upper limit for the normal range is 15 dB
HL.Different researchers have developed classications for the degree of hearing
loss. Table8.2 shows the classications developed by Goodman (1965), Jerger and
Jerger (1980), and Clark (1981). The classication developed by Northern and
Downs in 2002 can be primarily used to highlight slight hearing loss [7, 11–14]. The
type of hearing loss can be determined by comparing air conducted and bone conducted thresholds as either conductive, sensorineural, or mixed hearing loss. Further
assessment with speech audiometry and electrophysiological tests can help differentiate cochlear from retrocochlear types of sensorineural hearing loss.
The term “speech banana” shows the power distribution of the phonemes used in
speech plotted on the audiogram (Fig.8.1a). It is called thus because the area where
the vowel formants and the main energy of consonants are located resembles the
shape of a banana. Although the use of speech changes, the physiological process of
sound production remains the same across languages, and, hence, the speech banana
Table 8.2 Classications of hearing loss
Goodman
Degree of hearing loss
(PTA)
Normal <26 <21 -10 to 15 <16
Slight 16–25 16–25
Mild 26–40 21–40 26–40 26–30
Moderate 41–55 41–60 41–55 30–50
Moderately severe 56–70 56–70
Severe 71–90 61–80 71–90 51–70
Profound >90 >80 >90 >70
(1965)
Hearing loss range (dB)
Jerger and Jerger
(1980)
Clark
(1981)
Northern and Downs
(2002)
8 Behavioral andElectrophysiological Tests inAudiology
131
can be considered universal, with some caveats. For example, differences in the
phonetic structure across languages can cause differences in the nature and distribution of speech sounds within the speech banana [14].
The pure-tone average (PTA) is routinely calculated to determine the degree of
hearing loss. It is determined by averaging the threshold values at 500, 1000, and
2000Hz (PTA1). PTA2 is determined by the average of four frequencies: 500, 1000,
2000, and 4000Hz. PTA2 may be preferred, especially for high-frequency hearing
losses, to monitor how the hearing loss affects the audibility of speech sounds. PTA
helps measure and determine the degree of hearing loss by assessing the difference
in pure-tone thresholds and speech audibility between the ears.
When the audiometric assessment is completed, it is important to explain the
patient’s hearing status based on the audiogram. The following are examples of
phrases that can be used to explain the hearing status of a patient with increased
hearing loss at higher frequencies.
We gave you a hearing test in a quiet testing room and found the softest levels (hearing
thresholds) that you heard each tone, and plotted these levels on this graph. This graph is
called an audiogram. The audiogram has tones (frequencies) from low to high pitch on the
X-axis and intensity levels from softest at the top to loudest at the bottom on the Y-axis. Red
indicates thresholds for the right ear and blue indicates thresholds for the left ear [6]. Blue
and red symbols in the 0 to 25 decibels (or 15 decibels) range show normal hearing.
However, as you can see, you are not hearing well enough to detect high-pitched sounds in
both ears. This makes it difcult for you to hear speech sounds such as /s/, /sh/ and can
cause complaints such as ‘I can hear, but I can't understand.’
8.4.1.1 Masking
A “mask” is the term used in audiology to describe a distinct stimulus that raises an
acoustically obtained threshold. Masking is the presentation of noise to the non-test
ear (better ear) during audiometry to make it “busy” while assessing the test ear.
This is necessary when there is asymmetry in air conduction thresholds or a gap
between air and bone conduction thresholds. In these cases, when the stimulus is
presented to the ear being tested, it may be at an intensity level that can be heard by
the better ear. To prevent this, acoustic masking is required of the non-test ear. To
test hearing thresholds when masking is being used, the patient is instructed to
ignore the masking noise and respond only to the tones.
The noise used for masking is typically narrow-band noise in the frequency
range of the pure-tone signal. While the stimulus is presented to the test ear, the
noise is presented to the non-test ear. The air and bone conduction thresholds of the
poorer ear can be determined by carefully presenting the stimulus and noise at the
appropriate levels. Accurate masking levels are critical for accurate hearing threshold measurements. The “masking dilemma” occurs in cases with bilateral conductive hearing losses with an air-bone gap >40dB, where it is possible for the masking
in the non-test ear to cross over through the skull and affect the hearing threshold in
the test ear. Masking can also be difcult for certain patients, such as young children, who may not understand the instructions [4, 10].
132
E. Kösemihal et al.
The test signal may be heard in the non-test ear under the following conditions,
and, in these cases, masking should be performed for the non-test ear:
– For supra-aural headphones, when there is 40dB (60dB for insert earphones) or
greater threshold difference between the air conduction threshold of the test ear
and the bone conduction threshold at that frequency in the non-test ear.
– If both air conduction thresholds are 15dB or greater than the bone conduction
threshold at a given frequency (an “air–bone gap”).
Three essential variables must be known in order to perform masking correctly.
These are interaural attenuation (IA) for the transducers being used, threshold levels, and effective masking levels. Stimuli presented through the air undergo IA
(attenuation in sound energy across the skull) as they travel to the non-test ear. If the
stimulus is loud enough to be heard by the cochlea of the non-test ear, cross-hearing
occurs. For example, in the case of severe unilateral hearing loss, the unmasked air
conduction audiogram will reect a shadow of the normal ear, misleadingly indicating a much lower degree of hearing loss in the ear with severe hearing loss.
There are signicant differences in IA values depending on the type of transducer. The IA of supra-aural headphones commonly used in the clinic (e.g., TDH39)
is considered to be 40dB.Insert earphones have the highest IA of 60dB and therefore have less need for masking [8]. Disposable foam probes, which are attached to
the end of insert earphones and changed from patient to patient, provide comfort
and effectively prevent the spread of infection in the ear. However, insert earphones
may only be available in some clinics, and their use requires the ear canal to be clear
of signicant wax obstruction. Supra-aural headphones may cause the ear canal to
collapse in pediatric and geriatric populations. This can create a pseudo air–bone
gap, especially at high frequencies. Because the insert headphones are placed in the
ear canal, this collapse does not occur, which is another advantage over supra-aural
headphones.
The IA value for oscillator (vibrator) bone conduction transducers is 0dB.The
contralateral and ipsilateral cochleae can receive stimuli delivered by a bone vibrator placed on either mastoid with little or no attenuation. Masking is usually required
to determine ear-specic bone conduction thresholds when the air–bone gap exceeds
10dB [4, 8, 15].
Generally, air and bone conduction thresholds must be determined for both ears
to determine which ear and frequencies to mask and the minimum/maximum mask
noise levels to avoid under- and over-masking. The difference between the bone
conduction threshold of one ear and the air conduction threshold of the other ear, the
difference between the bone conduction thresholds of the two ears, and the difference between the air and bone conduction thresholds of the same ear can be used to
determine which thresholds require masking in order to establish the true threshold
[4, 15]. For symmetrical bilateral hearing losses, where the bone conduction threshold for one ear is within 10dB of the air conduction threshold at that frequency in
both ears, masking is not required as neither ear shows an air–bone gap and the
8 Behavioral andElectrophysiological Tests inAudiology
133
symmetrical hearing loss means that recorded thresholds do not reect “crosshearing” from a better ear.
The amount of effective masking is also important. The masking level is calibrated so that an increase in masking noise by 5dB in the non-test ear will raise
the threshold by 5dB in the test ear, if the response is coming from the non-test
ear. In the plateau masking method, the noise level is raised several times until a
stable test ear threshold is recorded. Narrow-band noise is used for masking to
determine accurate air and bone conduction thresholds in diagnostic audiology [4,
15]. Audiometers should be calibrated by the manufacturer or the calibration lab-
oratory to deliver appropriate levels of masking, known as “effective masking
levels.” The level of narrow-band noise required to effectively mask a tone is usually a few decibels above the level of the tone and is specied in audiometric
standards.
8.4.2 Speech Audiometry
Speech audiometry is a valuable method for assessing the functional perception and
hearing ability of people with hearing loss. It more accurately reects the individual’s hearing function during daily listening than pure-tone audiometry. It is evaluated using speech stimuli and tests that include threshold and supra-threshold
measurements. It can be used to cross-check thresholds obtained with pure-tone
audiometry, to indicate the location of the lesion causing the hearing loss, to evaluate the efcacy of hearing aids and/or cochlear implantation, and to assess central
auditory processing abilities. Testing can be done by monitored live speech or by
using recorded words. The use of recorded materials standardizes the testing procedure and is preferred to eliminate speaker variability and standardize intensity levels. Testing supra-threshold speech recognition with recorded materials has become
more accessible with the use of digital recordings that can be delivered via an external device such as a laptop or incorporated directly into audiometer software. The
use of carrier phrases is common for speech testing using recorded words. A carrier
phrase such as “Say the word ...” is used to draw attention to the word to be repeated.
The carrier phrase is present in the recorded material but can also be included when
using monitored live speech. The carrier phrase that precedes the test word should
cause the audiometer volume unit (VU) meter to peak at 0dB, with the test word
then delivered at the same level.
Three basic tests of speech audiometry are routinely used in conjunction with
pure-tone audiometry: Speech Awareness Threshold (SAT), Speech Reception
Threshold (SRT), and Word Recognition Score (WRS). The intensity levels used for
speech testing are expressed in dB HL.If both supra-aural and insert earphones are
used for speech testing, they should be calibrated separately as the threshold levels
for speech vary between these transducers. A description of the routinely used tests
is provided in Table8.3.
The SRT and PTA should correlate closely, with a maximum difference of ±7dB
between thresholds. If there is a larger discrepancy between PTA and SRT, it must
134
Table 8.3 Basic speech audiometry tests
Test name Explanation
Speech
Awareness
Threshold
(SAT)
Speech
Reception
Threshold
(SRT)
Word
Recognition
Score (WRS)
Most
Comfortable
Level (MCL)
Loudness
Discomfort
Level (LDL)
The lowest hearing level is when the presented sounds, syllables, or words
are noticed. Speech stimuli such as “ba-ba,” “da-da” /a/, /u/, /sh/, and //s/ are
presented. The frequency characteristic of the stimulus is used to determine
the individual’s hearing threshold at that frequency. For example, the /sh/
phoneme reects around 3000Hz
The SRT is the lowest intensity level at which the subject can repeat 50% of
the words presented. The words typically consist of two syllables with equal
stress on both syllables (spondees). The test begins at a comfortably
recognizable level. The intensity level is decreased by 10dB after each
correct repetition. The speech reception threshold is the lowest intensity that
can be repeated. The SRT usually correlates with pure-tone thresholds at 500
and 1000Hz
The WRS is determined using an open-ended test that evaluates speech
recognition. Approximately 40dB is added to the PTA or SRT, and stimuli
consisting of 25 monosyllabic words are presented to the patient through the
audiometer. Words are presented via a microphone (live audio) or as recorded
material. The number of words repeated correctly is counted, and the result is
expressed as a percentage. The WRS is 80% when 20 of the 25 words are
repeated correctly
Loudness rating is used to determine the most comfortable listening level for
the patient. The test begins by adding 25–40dB to the speech understanding
threshold. The patient is asked to listen to the audiologist’s voice by either
increasing or decreasing the intensity. The comfortable level is determined
using the phrase “The sound is low, loud, or most comfortable.” The WRS
test is performed at this level
LDL is the level at which the patient cannot tolerate the presented sound and
becomes uncomfortable. It is also referred to as the uncomfortable level
(UCL). It is performed with both speech and pure-tone stimuli. The patient is
told that the sound level will gradually increase and is asked to indicate the
level at which he or she becomes uncomfortable. LDL is approximately
100–110dB HL for people with normal hearing. It is used in hearing aid
tting and auditory rehabilitation planning
E. Kösemihal et al.
be investigated to rule out patient-related or technical problems. Repeating the test
instructions to the patient may be the rst step in the investigation [16].
The WRS test evaluates speech recognition rather than language comprehension
or understanding. Hearing losses vary in WRS based on the type of pathology,
degree of hearing loss, and hearing conguration. The WRS test is not designed to
distinguish between two similar sounds or words; this test simply requires the
patient to recognize the word. For this reason, it is more accurate to use the term
“word recognition,” rather than “speech discrimination.”
Phonemically balanced (PB) word lists are typically used for WRS.These lists
are designed to represent how vowels and consonants occur naturally in a given
language. Historically, 20 lists of 50 words called phonetically balanced (PB-50)
[17] were used in English. There are a number of different word lists, including
those created by the Central Institute of Deaf-22 (CID W-22) in the 1950s [18]; 4
phonetically balanced lists of 50 words (200 words in total) were created using
8 Behavioral andElectrophysiological Tests inAudiology
135
words from this list. Using the Northwestern University Number 6 (NU No. 6) test,
Lehiste and Peterson (1959) produced 4 different lists of 50 phonemically balanced
words in a consonant–nucleus–consonant (CNC) structure [19]. Both lists are still
in use today.
In addition to word recognition tests, nonsense syllable/phoneme recognition
tests can be used to test speech perception, reducing the advantage of word content
and word familiarity for patients with more advanced language skills. Nonsense
syllables are used in the consonant–vowel (CV) or vowel–consonant (VC) format.
The most prominent of these materials are the City University of New York
Nonsense Syllable Test (CUNY-NST) [20] and the Nonsense Syllable Test
(NST) [21].
Sentence tests are also widely used—sentences better reect everyday communication in which listeners have access to semantic, syntactic, and lexical cues, in
contrast to monosyllabic or nonsense syllables. For this reason, sentence materials
are widely preferred for hearing aid/cochlear implant applications. The most common of these sentence tests is the CID Everyday Sentences [22], developed by
Silverman and Hirsh (1955), consisting of 10 lists of 10 sentences, with each containing questions, commands, and statements with 50 keywords in each list. This
test is scored by calculating the percentage of keywords correctly identied. In addition to these tests, which are administered in a quiet environment, there are also
sentence tests that are administered in noise.
Speech testing in noise has become increasingly popular. The most common
problem for people with hearing loss is understanding speech in noise. People with
hearing loss require a higher signal-to-noise (SNR or S/N) ratio to understand
speech than people with normal hearing, and this effect is even greater for children
with hearing loss. There is variation across tests; however, studies have shown that
in general, for every 1-dB increase in speech signal over background noise, there is
a 3% improvement in signal recognition. Increasing the S/N ratio by 10 or 12dB
improves speech understanding by 30% [23].
The Hearing in Noise Test (HINT) and the Quick Speech in Noise (QuickSIN)
are common sentences in noise tests [24, 25], and the AzBio Sentence Test is
becoming increasingly popular [26]. The Synthetic Sentence Identication Test
(SSI), the Speech Perception in Noise Test (SPIN), and the Connected Speech Test
are additional sentence tests with specic applications [27–29].
The Matrix Test is an innovative approach to sentence testing developed in
Swedish by Hagerman in 1982, which has been translated and made available in
many languages on the basis of validity and reliability studies [30]. It uses an adaptive psychophysical method that measures speech recognition ability in either quiet
or noise using sentence materials that are syntactically consistent but semantically
unpredictable. The speech recognition threshold in noise is determined using an
adaptive signal-to-noise method to measure the S/N ratio in decibels. This and other
speech in noise tests can be performed via headphones or through loudspeakers in a
free eld, with speech and noise presented from the same or different directions.
Testing in the free eld better reects the communication environment and skills
needed for listening in real life.
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E. Kösemihal et al.
The developmental, rather than chronological, age of the child determines
which speech test to administer. Speech tests can be administered to children
similarly to adults, but tests administered to infants and toddlers who cannot
cooperate are different. In infants, speech stimuli can be presented during behavioral observation audiometry (BOA) and visual reinforcement audiometry (VRA).
During BOA testing, reexive or other behaviors can be observed in response to
moderately loud speech stimuli (e.g., stop suckling, startle, eye widening); however, these behaviors are difcult to observe and reect the minimal response
rather than threshold levels in young infants. VRA can be used to measure speech
detection thresholds in children who are able to make a reliable conditioned head
turn. Preschool children who recognize a speech stimulus but cannot repeat it can
be given instructions such as “Show me your mouth, show me your nose.” Using
a closed-set testing method, children can be asked to point to pictures or objects
when they hear a word. The sounds /a/, /i/, /u/, /s/, /sh/, and /m/, known as Ling
sounds, include low-, medium-, and high-frequency speech regions [31]. The
Ling test is often used to assess the audibility of speech sounds in individuals with
suspected or conrmed hearing loss or in those using hearing aids or implants.
VRA or play audiometry can be used to check detection of Ling sounds in young
children.
Word recognition ability is usually good in CHL, when speech stimuli are presented at sufciently loud intensity levels because normal cochlear function is present. By increasing the stimulus intensity, it should be possible for the word
recognition score to be either close or equal to normal hearing at a level that is
comfortably loud for the patient.
Cochlear dysfunction is associated with a lower WRS compared to CHL.Patients
with retrocochlear dysfunction typically have exhibit poorer word recognition performance, depending on the degree of neural hearing loss. Speech audiometric tests,
especially word recognition tests, are more sensitive to neural hearing loss than
pure-tone audiometry. WRS decreases when the signal intensity level increases
when there is neural pathology, which is known as the “rollover phenomenon.” The
intensity level at which the WRS is at its highest is called PB max. The intensity
above PB max at which the WRS is lowest is called PB min. Rollover can be calculated by determining (PBmin-PB max)/PB max. The results are consistent with
neural abnormalities when the ratio exceeds 0.35 or 0.45. This may vary depending
on the test material used [16].
Central auditory processing disorders (CAPDs) can result in difculties in
understanding speech or other complex sounds such as music in the absence of
reduced hearing sensitivity. In auditory processing disorders (APDs), the auditory
brain is unable to distinguish between certain sounds and to interpret some or all of
the sound information received by the auditory system. Differences may be
observed in speech tests depending on the location and degree of pathology.
8 Behavioral andElectrophysiological Tests inAudiology
137
Signicant differences can be observed between speech tests performed in quiet
and noise. For this reason, it is important to use speech in noise tests when CAPD
is suspected.
8.4.3 Pediatric Assessment
Developmentally appropriate testing techniques and strategies should be used in
the pediatric population. Age-appropriate behavioral assessment techniques can
be used for children older than about 6months of age (VRA, play audiometry)
and for adults with normal cognitive function. Objective measures are needed to
assess hearing in very young children and in children or adults with impaired
cognitive function. If infants and young children are unwilling to wear headphones, tests can be conducted with free-eld loudspeakers; however, every
attempt should be made to obtain separate ear information. Insert earphones are
preferred when testing young children as they are more comfortable and easier to
place on small heads. For free-eld testing, a loudspeaker in the soundproof
room can deliver signals to the patient sitting in the calibrated, marked location
[32]. The thresholds obtained in the free-eld loudspeaker tests are the thresholds of the better ear. Hence, hearing loss can be underestimated or overlooked
in the presence of asymmetric or unilateral hearing loss. For this reason, it is
essential to evaluate both ears separately using the OAE and auditory brainstem
response (ABR) tests described on the following pages if behavioral thresholds
have not been obtained for separate ears. In addition to the diagnostic hearing
evaluation, free-eld assessment of hearing thresholds with cochlear implants
can be performed. If multiple loudspeakers are available, evaluating localization
of sound is a useful test of functional hearing for people with hearing aids or
implants.
Infants and young children respond to sounds at different levels depending
on their age. For example, infants aged 0–6weeks may respond to a warble,
modulated tone at 78dB HL, while children aged 21–24months may respond to
the same tone at 26dB HL or softer levels. These are the minimum response
levels observed in behavioral assessment. The ABR test provides estimated
hearing thresholds close to the behavioral hearing threshold, even in newborns [33].
The techniques used to assess infants and young children vary according to
developmental age and/or cognitive ability and are grouped as follows. Even if
infants and very young children have normal or near-normal hearing, their response
level may be above the threshold. These responses are referred to as the “minimum
response level” to avoid confusion with the hearing threshold. Table8.4 lists the
behavioral tests that can be used according to age.
The protocol for administering the audiological test battery to children of different ages is provided in Table8.5 [34–36].