A guide to conducting speech
audiometry testing
Overview of this guide
Welcome to this guide on conducting speech audiometry testing. It will help
you to:
•
understand the purpose of speech audiometry
•
clarify what client information you need
•
outline the equipment you need
•
conduct the test
•
record and interpret the results, and
•
determine if your client needs a referral to either a general
practitioner or ear, nose and throat specialist.
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Speech audiometry
Speech audiometry is an important part of audiological assessment. We use
it to evaluate:

speech perception threshold

speech reception threshold, or SRT

speech discrimination ability, and

to check the validity of pure tone audiogram test results.
With this information the clinician can build up a picture of the client’s
needs to determine appropriate hearing aids.
Information needed before conducting
the test
There are some key pieces of information you will need before conducting
speech audiometry testing.
Ultimately, you are trying to work out if speech masking is required and if
so to what level.
Our ears can compensate for each other especially if the hearing in one ear
is better than the other. An audiometer can generate noise in the non-test ear
to mask or remove it from the test. This prevents the good ear from affecting
the accuracy of the results.
To determine speech masking follow these steps:
Step 1 - Obtain a pure tone audiogram for the client.
Step 2 - From the audiogram calculate the three frequency average hearing
level, or 3FAHL. This is calculated from the hearing threshold level, or
HTL, at frequencies of 500Hz, 1000Hz and 2000Hz.
Step 3 - The three frequency average is then used to calculate the
presentation level, or PL, for each ear.
Step 4 - Find the minimum discrimination score level, or MDSL, for the test
audiometer.
Step 5 - Use the three frequency average hearing level, the presentation
level, the minimum discrimination score level and the interaural attenuation,
or IA, to calculate the cross-heard signal. The cross-heard signal tells you if
the good ear is helping the bad ear.
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Step 6 - Find the effective speech masking level, or ESML, for the test
audiometer.
Step 7 - Calculate the level of masking required.
Understanding the audiogram
Pure tone audiograms contain several key features you need to understand to
be able to perform speech masking calculations.

the results for the right ear are shown as circles

the results for the left ear are shown as crosses

the horizontal or x-axis indicates frequency in hertz (Hz)

the vertical or y-axis indicates the hearing threshold level in decibels
(dB)

additional symbols are used to show left and right ear bone
conduction.
Calculating the 3FAHL and PL
To calculate the three frequency average hearing level and the presentation
level follow these steps:
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
Do the calculation for one ear at a time. Typically you start with the
ear showing the most hearing loss. In this example the left ear.

Read from the pure tone audiogram the hearing threshold levels, for
500Hz, 1000Hz and 2000Hz. These three frequencies are always
included in the test. Using the example audiogram start with the left
ear which has the lower level of hearing. Find 500Hz, drop down to
the hearing threshold, then look across at the value in decibels. In
this case it is 30dB. At 1000Hz the hearing threshold is 40dB. At
2000Hz the hearing threshold is 50dB.

Add all three hearing threshold levels together. The result in the
example is 120dB. Now divide by three to get the average. The
example three frequency average hearing level for the left ear is
40dB.

To calculate the presentation level add 30dB. 30dB is a standard
used to bring the presentation level up to a comfortable starting
point. In this example add 30dB and the resulting presentation level
for the left ear is 70dB.

Repeat these calculations for the other ear. In this example the right
ear shows 10dB for all three frequencies, so the average is 10dB.
Add 30dB to get a presentation level for the right ear of 40dB.
Calculate the cross-heard signal
The cross-heard signal is a measurement to determine if any of the test
sounds will cross-over and be heard by the non-test ear.
To calculate the cross-heard signal you need the following:
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
The three frequency average hearing level and presentation level for
each ear.

The interaural attenuation, or IA. This indicates the loss in energy as
sound passes from one side of the head to the other. For supra-aural
earphones the interaural attenuation is 40dB. For insert earphones
the interaural attenuation is 60dB.

The minimum discrimination score level, or MDSL. The MDSL is
pre-determined for each audiometer. If there is no value available
use -5.
The formula is - cross-heard signal equals presentation level of the test ear,
minus the interaural attenuation, minus the three frequency average hearing
level (bone conduction) in the non-test ear, minus the minimum
discrimination score level.
In the example, the cross-heard signal equals the presentation level of the
left ear which is 70dB, minus 40dB interaural attenuation for supra-aural
headphones, minus the three frequency average hearing level for the right
ear which is 10dB, minus minus 5 or plus 5 for the minimum discrimination
score level.
The resulting cross-heard signal is 25dB.
Does this level of cross-heard signal require masking? This is determined by
asking if the cross-heard signal is greater than or equal to the three
frequency average hearing level (bone conduction) of the non-test ear. In
other words will the non-test ear help the test ear?
In the example, the 25dB cross-heard signal is greater than the 10dB three
frequency average hearing level in the non-test ear. Therefore masking will
be required.
How much masking is required?
To calculate the level of masking required you will need the following:

The three frequency average hearing level, air conduction, for the
non test ear.

The cross-heard signal, and

The effective speech masking level for the audiometer you will be
using. The ESML is pre-determined for each audiometer. If there is
no value available and the audiometer uses speech-weighted noise,
use a value of 10.
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The formula is…masking level equals, the three frequency average hearing
level (air conduction) for the non-test ear, plus the cross-heard signal, plus
the effective speech masking level.
In the example, when testing the left ear, the masking level equals the three
frequency average hearing level (air conduction) for the right ear which is
10dB, plus 25dB for the cross-heard signal, plus 10dB for the effective
speech masking level.
The resulting masking level for the right ear is 45dB.
You now have all of the information required to conduct the speech
audiometry test.
What equipment will you need?
To conduct speech audiometry testing you need the following equipment:

An audiometer.

A pair of earphones - the example image shows a pair of supra-aural
earphones but you might also use insert earphones, and
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
Recordings of word lists. You may also provide the words to the
client through the audiometer microphone but you must ensure that
the client does not ‘lip read’ as you say the words.
Conducting the speech audiometry test
Here is an overview of the steps you need to take when performing speech
audiometry testing:
Step 1 - Make sure the client is seated comfortably before starting.
Step 2 - Give the client an overview of how the test will be carried out and
give them an opportunity to ask any questions.
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Step 3 - Place the earphones on the client and set the audiometer to the
presentation level for the test ear. Test one ear at a time and start with the
good ear.
Step 4 - Instruct the client through the headphones for any further
instructions.
Step 5 - Test the first word list. Use AB (Arthur Boothroyd) word lists
which consist of ten words per list and each word has three phonemes or
speech sounds. Also be aware that the words you use must be culturally and
age appropriate.
Step 6 - Record the client’s response as they repeat each word. If the client
gets all three phonemes correct, give a score of 10. Two phonemes correct, a
score of 7. One phoneme correct, a score of 3. If they cannot repeat the
word, a score of 0. Adding together all the scores in the ten word list will
give you a total score as a percentage.
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Step 7 - Determine the client’s speech reception threshold, or SRT. This is
done by incrementally decreasing the presentation level until the score is
close to 50%. Each decrease should be of 10dB and a new word list should
be used.
Step 8 - Determine the client’s PB maximum score, or PBmax. This is done
by returning to the starting presentation level and incrementally increasing
the level until the score is 80% or above. Each increase should be of 10dB
and a new word list should be used. A person with normal hearing would be
expected to score 100%. However, some people with hearing loss might
only score up to, say, 70%.
Step 9 - Determine the client’s PB minimum score. Once you have
determined the PBmax raise the presentation level by 10dB and test with a
new word list. If the client’s score decreases, raise the presentation level by
another 10dB and score again with a new word list. Continue this process
until the highest presentation level for the audiometer is reached. The lowest
score obtained is the PBmin and will be used to detect rollover.
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Step 10 - Repeat the test on the other ear, usually the worse ear. You may
have to apply masking on the other ear, so remember to set the audiometer
for speech noise for the non-test ear. Remember also that the worse ear will
likely have a different initial presentation level.
Step 11 - Create a performance intensity function graph, or PI graph.
Step 12 – Calculate the rollover ratio.
Remember to tell the client
You will need to provide the client with test instructions. Proper instruction
helps ensure that the test results are accurate and valid. There are a few
important things to remember to tell the client:
•
they will hear words through the earphones
•
one ear (the better ear) will be tested first
•
they need to repeat each word after they hear it
•
if they are unsure, they still need to repeat what they think they heard
•
if they cannot make out the word, they need to let you know
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•
each word list will be at a different volume
•
ignore any rushing sound in the other ear
•
they need to tell you if they are not comfortable, and
•
encourage the client to ask questions.
Here is an example of an audiologist instructing a client before a test:
“Okay Audrey, we’ve finished your audiogram now. We’re going to do
some speech testing now. I’m going to put some words into your ears and
I’d like you to repeat each word as you hear it. If you’re not quite sure or
you think you missed a little bit, that doesn’t matter, I’d like you to repeat
just exactly what you heard.”
Performance intensity function
A performance intensity function graph shows the percentage scores from
the speech discrimination test (the performance) against the presentation
levels (the intensity). This graph can provide useful information towards an
accurate diagnosis.
A minimum of three word lists must be tested for each ear before creating
the graph. This should be done at the initial presentation level, 20dB below
and 20dB above. Where possible four word lists per ear are preferable.
In the example graph the blue line shows the normal increase in speech
discrimination scores as the presentation level increases and soon, responses
are 100% correct.
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Even with normal responses, you can still use PI function graphs to detect
possible central lesions. Compare the PI graph of each ear to check if there
is a significant difference between ears. ‘Significant’ means 20 to 30 percent
difference and indicates that the client has a central lesion.
The red line also shows a normal response but shifted to a higher dB range
indicating conductive hearing loss.
The purple line shows slight rollover, where an increase in presentation
level does not have a corresponding increase in speech discrimination score.
The green line shows significant rollover. Note the difference between the
performance at 70dB (PBmax) and at 90dB (PBmin).
Rollover
Rollover occurs when a client’s speech discrimination score decreases even
though the presentation level is increased.
The presence of rollover can indicate a lesion on the side of the brain
opposite the ear with the roll-over, or 8th nerve lesions on the same side.
Calculating the rollover ratio can give you a better idea of which lesion type
is present.
The formula for rollover ratio is: PBmax, minus PBmin, divided by PBmax.
In the example PI function graph (the green line) the rollover ratio equals,
65, minus 35, divided by 65, which equals 0.46.
A rollover ratio of 0.4 suggests cochlear lesions.
A rollover ratio of 0.45 or greater is a significant rollover and suggests 8th
nerve lesions.
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Cross-checking the results with the
audiogram
Cross-checking the results obtained from speech audiometry tests with a
pure tone audiogram can help validate your test results. This is particularly
useful if you suspect a client is malingering or exaggerating their hearing
loss. It is quite hard to fake a speech test to the same extent that you can
fake a pure tone audiogram.
The three frequency average hearing level from the audiogram should
closely match the speech reception threshold from the speech audiometry
tests.
In the example results both the three frequency average hearing level and
the speech reception threshold are 40dB. This helps validate the results and
shows that the hearing loss is real.
Explaining the results to the client
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Here is an example of an audiologist explaining the results of a pure tone
audiogram and speech audiometry tests to a client.
“Now that we’ve done all the testing, I need to explain to you what we’ve
done. We have the audiogram here, that’s a graph of your hearing. The red
circles demonstrate the levels at which we recorded your right ear, that’s
the levels you can just hear sound and the blue crosses show the levels for
your left ear. As you can see the left ear is a little bit worse than the right
ear. Anything down to this 20 dB line would be considered within the
normal limits, so your right ear is completely within normal limits, where
we expect it to be. Your left ear is a little bit below that, and we would call
this a mild to moderate hearing loss – and it’s a permanent type of hearing
loss.
When we did the speech, we tested you at different levels and in the right ear
you did very well all along. Everywhere we expected you to score. In the left
ear, we had to turn the sound up a little bit for you to hear the same amount
but you’re still hearing relatively well in that ear, as long as we turn up the
volume for you. Sounds you particularly had problems with, were the high
frequency sounds so for example the word fake you said fate, for chime you
said time, that’s very common, so in this speech banana you can see that the
high frequency sounds which are words like “th”, “ter”, “ker” are in the
high frequencies and therefore, you’re having trouble hearing those in the
left ear.”
Further tests
Following speech audiometry testing you may conduct further tests include
tympanometry and acoustic reflex testing. They are tests to see if the middle
ear is functioning properly.

Tympanometry (or impedance testing) is conducted to test the
volume of the ear canal, the air pressure of the middle ear, and the
compliance of the tympanic membrane.
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
Acoustic reflex testing checks the function of the stapedius muscle
tightening the stapes. This is done by subjecting the ear to a loud
noise to test the reflex function of the muscles.
Remember that your referral decisions should not be made on the basis of
speech scores alone. Speech testing is part of a battery of hearing tests and
all test results should be analysed in conjunction with each other.
Credits
Published by the Centre for Learning Innovation (CLI).
CLI would like to acknowledge the following people and organisations who
have contributed to the development of this resource:
Subject consultants:

Signe Peitersen

Bettina Turnbull
Reviewer: Peter Robinson
Location photographs taken at Connect Hearing, Lane Cove.
Copyright
© State of New South Wales, Department of Education and Training 2008
Copyright of this material is reserved to the Crown in the right of the State
of New South Wales. Reproduction or transmittal in whole, or in part, other
than in accordance with provisions of the Copyright Act, is prohibited
without the written authority of the Centre for Learning Innovation (CLI).
This resource has been developed under the agreements and sponsorship of
TAFE NSW. Copyright of this material is reserved to the Crown in the right
of the State of New South Wales. Reproduction or communication in whole,
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or in part, other than in accordance with the provisions of the Copyright Act
is prohibited without written authority of the copyright owners.
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resource, CLI has used its best endeavours to ensure that the information is
correct and current at the time of publication but takes no responsibility for
any error, omission or defect therein.
To the extent permitted by law, the Department of Education and Training
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