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ComD 3700 Basic Audiology
Lesson 5
Pure Tone Audiometry I
Highlighted information refers to a change between the audio recording
(using 10th edition) and the 11th edition of the textbook
1. ComD 3700 for distance education. This is lesson 5, Pure Tone
Audiometry I. This is the first of two lessons dealing directly with pure tone
audiometry. We will be covering chapter 4, pages 71-87. Hopefully we have
learned enough to lay a foundation for moving into pure tone audiometry.
We’ll be discussing delivering a test with the proper equipment and test
procedures.
2. The five factors need to be aware of when performing audiometric testing
are: the test equipment, environment, the patient, the clinician and the test
procedure. We'll discuss more specific elements to each of the categories.
Usually if these five are in order, we'll end up with a successful pure tone
audiometric result.
3. First, we need to consider our testing equipment, our audiometer and
other ancillary equipment. One concern is calibration of equipment. Is the
equipment functioning as it was intended and as the specifications
indicate? We have reviewed the ways of checking our calibration. There are
set rules and recommendations we have discussed of how to accomplish
those calibration procedures. We also discussed audiometers in lesson 4.
The audiometer is your testing instrument. This is what the examiner will
be using to examine a patient's hearing. We have looked at drawings and
pictures of a basic pure tone audiometer, like the picture on the top right.
There are times when a portable audiometer is necessary. The smaller
picture is a portable audiometer. You can see if the lid is shut down; there is
a handle on the front of the audiometer. It appears as a small case that you
can put in your car and run off to a school or other location to test hearing.
However, most of the testing audiologists perform will be done with a
diagnostic audiometer. The testing we will be discussing from now on will
require a diagnostic or clinical audiometer. These audiometers have the
capability of delivering a number of audiometric tests for the examiner. As
you can see from the picture, the diagnostic audiometers in use today are
much more sophisticated than the audiometer drawings we have been
using to learn the basics.
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4. One thing we haven’t discussed about the audiometer are the output
limits in terms of intensity or dB. As you can see, I've divided this into the
lower intensity limits and the higher intensity limits. Audiometers can
deliver tones at the different frequencies, at the minimum of zero dB and
most can deliver a tone at minus ten dB. As we test a person's hearing
acuity in the clinic, it is not general practice to investigate whether or not
they can hear tones at minus five and minus ten dB. Usually, if the person
can perceive the stimuli at zero dB, that is sufficient and usually marked on
the audiogram at zero dB. But there are times when the threshold is
determined into the negative level. Note the higher intensity limits. Here I
have delineated the different frequencies down the left hand side from 125
Hz to 8000 Hz. If you have your audiometer set to deliver the sound via air
conduction, there are some limiting constraints on the audiometer to the
upper or higher intensity level units that are available. For instance, you
can see that at 500, 1000, 2000 and 4000 Hz, the maximum output of the
audiometer is 110 dB HL. However, if you go down to 125 and 250 Hz, you
can see the levels vary. Now if I were to put another audiometer in place of
this one, the limits might vary slightly. This is just an example. Between 125
and 250, you can see this audiometer has an upper higher intensity limit of
75 dB HL at 125 Hz and 90 dB HL at 250 Hz. Then if you go all the way to
the bottom at 8000 Hz, you can see this audiometer will produce 90 dB at
its higher intensity level of 8000 Hz. Now, observe the bone conduction
limits. This particular audiometer just doesn't deliver a stimulus at 125 Hz.
Some audiometers don’t. On this audiometer, the upper limit for bone
conduction is 40 dB at 250 and then 65 dB HL at 500, 1000, 2000 and
4000 Hz. At 8000 Hz, this audiometer doesn't deliver a tone at all via bone
conduction. So, between air and bone conduction, the upper limits are
higher using air conduction. The audiometer is capable of producing
greater dB outputs for air conduction outputs overall than it is for bone
conduction vibrators on the side of the head.
5. As I mentioned in the previous slide, if you compare air conduction and
bone conduction upper intensity limits for the audiometer, you will note the
audiometer produces lower intensity limits for bone conduction than it
does for air conduction. The reason for this mostly is that more power is
needed to drive a bone conduction oscillator than the diaphragm in the air
conduction outputs. When bone conduction is driven at high intensity
levels, harmonic distortion can result. What that means is if we're putting
into the system 1000 Hz, and we're overdriving the system to a point of
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harmonic distortion then we might actually see at the output not only of the
1000 Hz we put in but we would see outputs at 1500 and 2000 Hz also. In
addition to all of this, there is the problem of tactile sensation, which can
occur. This means you drive the bone oscillator so strongly it moves
physically to the point the person can detect the movement on the side of
the head and may misinterpret that as the delivery of a pure tone stimulus
or hearing stimulus instead of a tactile stimulus.
6. In discussing the test environment, the greatest concern is the
background noise that may be present. This can affect the results by
elevating the thresholds of the patient. There are 3 major ways that the
ambient noise in the room can be attenuated: earphone enclosures, receiver
inserts and sound treated chambers. On the right, we have a picture of an
earphone enclosure device. It is hard to tell, but the supra-aural earphone
and cushion is mounted within a larger cup, which assists in the
attenuation of background noise. On the left are insert earphones. There
are advantages to insert earphones, particularly the exclusion of external
noise. They also have some effect on cross hearing masking and delivery of
the stimulus that we will discuss later.
7. The other factor is the room where the testing will take place. As you may
well understand it would be hard to accomplish a valid audiometric test
result in a noisy environment, like a street corner or park. You would rather
have a quiet environment or an environment conducive to good hearing.
Ideally, every hearing test should be done in a controlled environment,
either a sound booth or sound treated room. In any other environment,
every precaution should be taken to ensure that the test environment is as
quiet as possible. Turn off fans, unplug appliances, do whatever you can to
improve the validity of the test results. However, in audiometric
evaluations, particularly a clinical situation, the patient is placed in an
environment that we most often call sound treated rooms. I emphasize
sound treated. Some people call them sound proofed rooms, but they're
not. The room patients are tested in have some noise floor to be dealt with
or recognized. But the environment of a sound treated booth has been
designed, manufactured, and available for audiometric testing. There are
audiometric booths that are single walled and others that are double walled
booth. The double walled booth will to a help to attenuate as much external
noise as we can. There are also one-room and two-room audiometric suites.
The picture on the left is a one-room booth. So the patient is inside of the
booth and the clinician sits outside of the booth in the room. In a two-room
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suite, the patient is in one sound-isolated chamber and the clinician is in
another chamber. There is a window that provides visual communication
between the two rooms. There are also electrical connections that pass
through between the two rooms so that the signals can be directed from the
audiometer to the earphones. There will also be a talkback device that
consists of a microphone, amplifier and speaker and/or earphone that
enables the examiner to hear the patient when they speak. It's not as
imperative that the examiner room be double walled as the room that
houses the examinee. However, if possible, it is preferred.
8. The patient is another factor we have to deal with in getting a good pure
tone audiometric result. Patients come in a great spectrum of variety from
those who are highly motivated and respond well, understand the test
procedure well, and are alert and ready to be tested, to the other end of the
spectrum, to a patient that may be inadequately motivated for a variety of
reasons. Some patients may be physically or mentally disabled. There are
patients who are consciously trying to not be motivated and are trying to
bias the results of the exam. The patients come from all age groups from
very young to very old. In this course we are only discussing the testing of
adults. As we attempt to get a good audiometric result from a patient, we
need to have an assessment of the patient and their capabilities and some
opinion as to what type patient we're dealing with and what their
capabilities are. Most of the time there will be a place on the audiogram
where you indicate the reliability of the exam; good, fair or poor. This
indicates whether the patient was really performing adequately or whether
there was doubt as to the validity of the test result. The patient needs to
communicate with the clinician to let them know that they have heard the
stimulus. This can be done by having the patient raise their hand, raise
their finger, push a signal button or verbally answer that they have heard
the tone. There are positive and negative aspects to each. I prefer to use a
signal button as long as the patient is physically able to push the button. I
have found that it is the fastest way to get the response from the patient.
9. The next factor is the examiner or clinician. Usually this will be an
audiologist. We assume this is a sophisticated examiner. When we say
sophisticated, we mean the examiner has been properly trained,
understands all of the factors that come into play on a successful
audiometric test result: the patient, the equipment, the test procedure, and
other factors that may come to bear. If the examiner is poorly trained or
does not understand test procedure protocol or the patient and the
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environment, it's almost certain the test result will not be accurate.
Therefore, the patient's hearing will not be properly examined. As we have
proceeded through the course of history and the sophistication of
equipment from tuning forks to our modern day electronic devices,
different test procedures have been developed, advanced, and
recommended for our use in evaluating hearing or hearing disorders of
patients. Not only have new test procedures been developed, but older test
procedures have also been modified. These test procedures have been
researched thoroughly. Some of the inadequacies in test procedures have
been exposed and the test procedures have been refined over time. If they
are not followed as indicated or taught the test result can be different. This
can be a hazard to the patient, the audiologist, and the others involved. So
it's quite important that the examiner understands test procedures and test
protocol and carries them out properly. Before conducting threshold
testing, the clinician should obtain a complete case history and otoscopy
needs to be performed. Visual inspection of the pinna and ear canal,
including otoscopy, should precede audiometric testing to rule out active
pathological conditions and the potential for ear canal collapse caused by
audiometric earphones. The ear canal should be free of excessive cerumen
before testing. The audiologist should be able to monitor the listener's
alertness and physical condition at all times. The clinician also needs to
make sure that the patient is in the correct position for testing. It is best if
the patient is seated facing slightly away from the clinician and audiometer.
The patient should not be able to observe visual cues from the clinician
while they are being tested. But the clinician should be able to observe the
responses of the patient. So, it is recommended that the patient be seated at
a right angle to the clinician, like shown in this picture. The other
responsibility of the clinician is giving proper instructions to the patient.
10. Giving proper instructions to the patient are extremely important and
cannot be over-emphasized. Depending on the instructions given, the
patient’s audiogram can differ by as much as 10 dB. Once you place the
headset is on their ears it is difficult to communicate with the patient.
Shouting is not an effective method. So either instruct the patient prior to
putting on the headphones or through the microphone. Too many people
tend to over instruct the client. We get into a professional mode and have
learned a professional language, then face people who are coming in who
are not educated to this in house language we use. In our instructions, we
over instruct or make their understanding almost impossible. For instance,
in our instructions, we may use the term frequency. “Mr. Jones, you'll be
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hearing a number of different frequencies.” What we should probably say
is, “Mr. Jones, you'll be hearing a number of different tones. Those tones
will have different pitches”. Also we could say, “Mr. Jones, you'll hear tones
with different intensity levels”. But it might be better to say, “Mr. Jones,
you'll be hearing a number of different tones with different loudness levels.
Some will be loud or more intense, and some will be rather soft”. Tell the
client what you expect of them in terms of a response. In most normal
audiometric settings, the response is a raised hand. If using the raise hand
method, then I like to instruct them to, “raise your hand each time you hear
a tone and when the tone goes away, put your hand down”. Some clients
will raise a hand and when the tone is stopped, the client sits in the other
room with their hand in the air for a period of time. It is important to
instruct them to raise their hand (or push the button) every time they hear
the tone, no matter how quiet it is. It is also recommended that the clinician
ask the patient if they understood. So an example of proper instructions
may sound like this, “Beginning with your right ear first, you will hear a
tone, a buzzing sound. Some of the tones will be loud and some will be soft.
They will vary in pitch. I want you to raise your hand when you think you
hear the tone and lower it when the tone goes away. Please raise your hand
whenever you think you hear a tone, no matter how quiet it is. Do you have
any questions?” After the instructions have been given and understood,
then you will have the patient remove their glasses, hearing instruments (if
wearing them) and large earrings if using supra-aural headphones. If using
insert receivers then glasses and earrings will not interfere. It is standard
practice to begin testing with the better ear first, if it is known. This is not
vital. You can test either ear, but usually, you'd like to get a result from the
best ear before you attempt to test the poorer ear. The client is asked,
“Which is your better ear?” Many times, they can tell you this. Sometimes
they will not. If the patients is unsure which ear is best, then most clinicians
begin testing in the right ear, but there's nothing to say you have to start
with one or the other. But it seems logical we'd start by testing the better
ear. When a patient fails to respond to a stimulus this is called a negative
response. If the signal has actually not been heard this is a true negative. If
the patient hears the signal but does not respond this is a false negative and
can be caused by a variety of factors.
11. When placing the earphones on the patient's head make sure the center
of the earphone or diaphragm over the external auditory meatus or the ear
canal is not pressed up against a portion of the pinna or another part of the
head. Also, ensure that the tragus is not pushed inward blocking the sound,
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which would not be good. Sometimes the client will adjust the ear phone a
bit after you've placed it on his head. I don't see that as problematic if
they're not adjusting it dramatically out of place. They may feel it needs to
be centered more or it's more comfortable in a different position, which is
fine. It's not going to change the test result unless it's a dramatic change in
the way you placed the earphone on the head. Here is a picture with a
young man with a set of supra-aural earphones in place. You can see an
earphone on each side with the cord coming down. The headband goes up
across the head. It's not greatly noticeable but those headbands and
earphones have an adjustment. You see that metal stem running above and
to the right of the earphone. That can be adjusted to fit the head
comfortably. This puts the earphone in a proper position. Below that is a
picture of him with the bone oscillator placed in a proper position with the
headband running up across the head and the other side has the white
plastic plug so it doesn't dig into the head. You can see the plastic box
placed down behind the auricle on the mastoid process, then the cord
running off down to the audiometer. This picture is interesting, the way this
headband is placed to hang on, due to the density of this client's hair.
Usually the headband is placed a little more forward than that (unless you
have a patient with this fine hairstyle!) But this is a good placement, you
just need to make sure that the headband is going to stay on and keep that
bone oscillator in place.
12. Another important factor in audiometric testing is 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. The
use of disposable acoustically transparent earphone covers or disposable
insert earphone tips is recommended. Hand washing should be routine for
the audiologist between patients.
13. So now that the patient has been adequately instructed and is placed in
a proper environment with a clinician prepared to use the equipment, then
the testing can begin. The purpose of pure tone air conduction testing is to
determine the threshold of the patient at every test frequency. I think we've
mentioned the word threshold a lot, but I want to make sure that it been
defined for you. Threshold is the quietest level the patient can hear the tone
50% of the time, just half or more of the times that you present it. To play
on this a little bit, particularly with pure tone audiometry, we are interested
in finding the client's threshold. So, at a given frequency, for now, let's say
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1000 Hz, we would like to learn how that client hears at 1000 Hz. So we will
present pure tones to the client at different intensity levels under a
procedure. Then we will increase and decrease the intensity of the stimulus
tone. We find a place where the client can hear and indicate that he hears
the stimulus fifty percent of the time. In testing, we lower the intensity of
the stimulus until the client would no longer be able to perform at fifty
percent response. And of course if we raise the intensity level, the client will
not only probably be able to give us a fifty percent level but probably a
hundred percent if we are above threshold. The minimum number of
responses needed to determine the threshold of hearing is two responses
out of three presentations at a single level. The objective is to find a level
that satisfies the requirement. We will be learning how to obtain a
threshold in the next lesson.
14. The threshold is then charted on an audiogram. These are examples of
charts where we place the results of the audiometric pure tone testing. We
use pure tones as the stimulus to test an individual's hearing acuity. As we
do, we place the results on the graphs so we have a picture or record of their
hearing. I know we studied the audiogram already, but I want to review it
and give you some additional information. The audiogram on the left is
more typical of one that would be used in a clinic. Let's review the
audiogram. The vertical lines on the audiogram represent the frequencies
corresponding to the audiometer dial. The lowest test frequency is 125 Hz.
However on this audiogram, the frequencies begin at 250 Hz. You will see
this sometimes. The highest frequency is 8000 Hz, on the right. Octaves are
arranged in numerical order across the top of the audiogram. Remember an
octave is when the higher frequency is double the lower frequency. When
you double 250 Hz, then the interval between 250 Hz and 500 Hz becomes
one octave. One octave is from 250 Hz is 500 Hz. There are six octaves from
125 Hz to 8000 Hz. The half octaves are also represented on the bottom of
the audiogram, 750 Hz, 1500 Hz, 3000 Hz and 6000 Hz. There is also a
doubling from half-octave to half-octave. The horizontal lines of the
audiogram represent the intensity in dB HL, from minus 10 dB HL at the
top to 110 dB HL at the bottom. That's as intense as we'll usually test,
although some audiograms will list until 130 dB. I included the audiogram
on the right to help you understand the frequency and intensity of some
environmental and speech sound. This audiogram of familiar sounds can be
used in counseling the patient, so that they understand the impact that
their hearing loss has and what sounds they are missing. If their hearing
thresholds are below a certain environmental sound or speech sound, they
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will not hear it.
15. In describing the audiogram, sometimes the terms ordinate and
abscissa or X axis and Y axis are used. Dr. Laws taught me this hint about
remembering which is the X axis and which is the Y axis. The Y axis is the
ordinate and the X axis is the abscissa. So, it can be helpful when you're
trying to remember which is the abscissa and which is the ordinate, you
pronounce or-din-ate. You tend to put your lips in a position where they are
vertical. When you say abscissa, you put your lips into this pulled back from
ear to ear or side to side or this horizontal position, which represents the
abscissa on the left to right axis. This is a great piece of information, which
I’m sure you’ll carry throughout your life.
This is listed incorrectly on the slide: Frequency should be listed as being
recorded on the X-axis. So it should read:
X axis=abscissa=frequency in
Hertz
and Y axis=ordinate= intensity in dB HL.
16. In a clinic, when you ask for a patient's audiogram, you're usually asking
for a form similar to these examples with this information printed on it.
Even though you probably can't read these very well, we'll review some of
what is included, so don't get frustrated. These are just samples to give you
a general idea. Every clinic will have a version of its own. Somewhere on the
audiogram will be the clinic information; their name, the telephone
number, and address. Information about the patient will also be listed.
Usually included at a minimum is the patient's phone number, address,
date of birth, and the date of the examination. There are also places is
where we put different test results that are not particularly pure tone
audiometry but speech audiometry, tympanometry results, and information
such as that. The audiogram on the left is set up so you have a right ear and
a left ear test result charted separately. On the right, you'll see another
arrangement where both ears are placed on one chart. For teaching
purposes, I really like the two chart arrangement. But in most clinics, the
audiogram is one chart, and the symbols are placed on the one chart. Even
thought the worksheets may look different, there are similarities among
audiograms.
17. Here is a copy of the audiogram that we use at the Utah State University
Hearing Clinic.
18. Audiograms usually have a symbol legend. This is a sample of a legend
or the key to symbols on an audiogram. These symbols are used to mark the
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thresholds of the patient. Usually there is a right column and a left column
under the legend. Mark threshold with a circle “O” in red for the right ear,
and an “X” in blue for the left ear. The easiest way to remember these
symbols and colors is by the three R’s- Red, Right and Round. The symbols
for air conduction are uniform worldwide, as is the color code, red for the
right ear and blue for the left. Below the O and X, notice the triangle and
the box. These symbols are used if you have used masking while testing. If
you are masking the best ear, you would use a triangle in the right ear
indicating the left ear was masked. We would use a box on the left ear
where the stimulus is going to be delivered to indicate that that's the result
of their hearing while the right ear was masked. Go down below the triangle
and the box to the next two symbols, those that look like greater and less
than. Those are bone conduction symbols without masking. So if we put the
bone oscillator on the head and are going to deliver a tone and will get
hearing results by a bone conduction, we will record those hearing results
on the right audiogram with the symbol that is open to your right. We will
place them accordingly on the right ear audiogram. We will take the other
symbol that is open to the left and use it on the left ear audiogram to
indicate the bone conduction thresholds on that ear. Below that, you can
see the bone conduction symbols for when masking has been used. The
next symbol, the letter “S” indicates that testing has been done in the sound
field. This means that testing was done using the speaker system rather
than headphones. An “A” is used if testing is done with the patient’s hearing
instruments. Missing from this chart are the no response symbols. They can
be found on page 94 of your book. Basically you can attach an arrow
pointing down to the left or right to the symbols above to indicate that
you've reached the limit of the audiometer for that frequency and you have
not been able to obtain a response from the patient. The little man at the
top is a good reminder of the right and left symbols for air and bone
conduction. If you go back and review this, it will be good for you. Your task
is to continue to review until you feel good about knowing those symbols
and which ear they go to and if they're an air conduction or bone
conduction symbol.
19. Now we will learn how to record the symbols. The threshold is recorded
on the frequency line where the frequency and the intensity in dB HL
intersect. Here's an audiogram where you place the results from both ears
on the same chart. You don't have a legend so you'll have to remember the
O's are for right ear air conduction and the squares are for left ear air
conduction masked. Then you put the little open boxes on there for the left
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ear for masked bone conduction and the open triangle for the right ear bone
conduction. Remember, blue for left ear and red for right ear. This is a
typical audiogram with the threshold of both ears charted on the same
graph. What I want you to do is notice the actual placement of the symbols.
Let's start with the right ear. Look at air conduction at 500 Hz. If the
threshold was 10 dB, then we would place the O at the junction of 500 Hz
and 10 decibels. Look under 4000 Hz, if the threshold was 25 dB, we would
place the O halfway between 20 and 30. That is the correct placement. Now
refer to the left ear, you can see the square over 40 dB at 500 Hz and 55 dB
at 1000 Hz. For bone conduction first let's go to the right ear at 1000 Hz. If
the threshold was 20 dB, we would place the symbol for bone conduction so
that the open triangle was right at 20 dB. If threshold happened to be 25
dB, we would place the bone conduction symbol halfway between 20 and
30, like it is placed at 2000 Hz. Take note that we place the symbol on the
left side of the ordinate line. The symbol is just to the left of the line. On
the left ear, the bone conduction symbols are placed just to the right of the
ordinate lines. Let's go back to the right ear for air conduction, the O at ten
dB at 500 Hz. If the bone conduction happens to be at the same dB level,
you don't place the symbol for bone conduction level right on top of the O.
You place it off to the left side. Hopefully this will help you to understand
the proper placement of the symbols on the audiogram.
20. Once you have determined the thresholds of each frequency you can
begin to classify the degree of hearing loss. The first step of this is to
determine the pure tone average or PTA, not to be confused with the parent
teacher association. The pure tone average is usually found by averaging
500, 1000, and 2000 Hz. I don't know if I've said this before, but the
speech frequencies are between 500 and 2000 Hz. So those three
frequencies are on the pure tone audiogram but also represent the speech
frequencies for good reason. Most speech sounds we utter have a frequency
that would fall into that corridor between 500 to 2000 Hz. There are
certain conditions, such as when there's a 50 dB difference between
adjacent frequencies, that the pure tone average might be computed
between the high two frequencies of these three. Let's not worry about that
now. Let's focus on the pure tone average. Once we have an audiogram and
have found the threshold for all frequencies in both ears, we are going to
look at their threshold at 500Hz, 1000 Hz, and 2000 Hz. Then we'll
compute our pure tone average from that. When we look at the audiogram
on this slide, at 500 Hz, the client's threshold in the left ear is 10 dB. At
1000 Hz, the threshold is 15 dB. At 2000 Hz, the threshold is 30 dB. If we
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add those up, we’ll get 55. Then divide that by three, which is 18. So 18 dB is
the PTA for the left ear of this client. If you look at the right ear, you can
determine that the PTA is 57 dB. The PTA is useful for predicting the
threshold for speech as well as establishing the degree of communication
impact imposed by a hearing loss. So one of the ways we use the pure tone
average is to help define the degree of hearing loss.
21. We can often assume that someone has a hearing loss because we have
to talk at a louder level than normal in order for them to hear us. Even
though we cannot directly experience the degree of that person’s hearing
loss, we can appreciate its magnitude in terms of how loudly we must speak
to be heard. This is certainly not the only manifestation of a hearing
impairment, but it does highlight an important point: we can quantify the
degree of a patient’s hearing loss in terms of the level of the stimulus
needed for them to respond to it. This is known as the classification of loss.
This is used for reporting the degree of hearing loss to the patient and also
in the diagnostic reports that are written. This can help to define the degree
of communication impact of a given hearing loss. This classification will
help when we begin to define the degree and type of hearing loss based on
the audiometric results. So we can use our audiogram and the pure tone
average to define the degree of loss. There are several different scales that
vary slightly. But we will refer to the scale used in this slide. The scaling
gives us the different degrees of impairment; this is how we speak to each
other. We say the client has a mild sensorineural hearing loss or a
moderately severe hearing loss or a moderate conductive hearing loss. We
can see the dB categories you fall into to get a degree of hearing loss on the
right. Anyone with minus 10 to 15 is normal. 16-25 you have a slight hearing
loss and on down. Anything greater than ninety dB is a profound hearing
loss. So let's take our patient from the previous audiogram. We calculated
that their PTA was 18 dB in the left ear. This would be considered a slight
hearing loss. In the right ear, the PTA was 57 dB. So they would have a
moderately severe hearing loss in the right ear, based on the pure tone
averages. It is important to remember that a person with hearing loss
usually has a different amount of loss at each frequency across the range of
hearing. For example, a person may have normal hearing in the lower
frequencies, a moderate loss in the mid-frequencies and a severe hearing
loss in the higher frequencies.
22. As we have discussed audiometric testing and will continue to discuss it
in more detail in this lesson, I am hopeful that you will start to determine
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associations that are made between the anatomy of the ear, the test results
or type and degree of hearing loss and possible disorders. So, if you test a
patient and get a certain type of test results, your mind should shift into
thinking about the anatomy of the auditory mechanism. In other words, if I
give you an audiogram that indicated conductive hearing loss, you would
think of a disorder that affects the outer and/or middle ear. We will discuss
specific disorders later in the course. But if I gave you a disorder, then you
should be able to think of the anatomy and also be able to associate a test
result. So you need to be able to associate between these three. Start
thinking this way and it will help you in the future.
In conclusion, in this lesson we learned about the five factors we work
with in audiometric testing: the test equipment, environment, the patient,
the clinician and the test procedure. In the next lesson we'll discuss more
specific elements about the testing procedure. We will learn about proper
procedures for air-conduction audiometry, bone-conduction audiometry
and audiogram interpretation.
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