Download Certificate IV in Audiometry HLT02-8–3064

LEARNER RESOURCE
Certificate IV in
Audiometry
HLT02-8
3064-8/HLSP
Version No. 1
Community Services, Health,
Tourism and Recreation
Curriculum Centre
Health and Life Sciences
Programs
3064-8/HLSP Certificate IV in Audiometry - Equipment V1
3064-8/HLSP Certificate IV in Audiometry - Equipment V1
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Acknowledgments
TAFE NSW - Community Services, Health, Tourism and Recreation Curriculum Centre
would like to acknowledge the support and assistance of the following people in the
production of this resource package:
Writer:
Gloria Armstrong
Audiometrist
Clinical Practice and TAFE NSW
Project Manager:
Gary Wood
Program Manager
Health and Life Sciences Programs
Enquiries
Enquiries about this and other publications can be made to:
TAFE NSW - Community Services, Health, Tourism and Recreation Curriculum Centre
Locked Bag No. 6
MEADOWBANK NSW 2114
Tel: 02-9942 3200
Fax: 02-9942 3257
T:\Health and Life Sciences\Courses\Audiometry 2004\equipment hlt02 8 audiometry.doc
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TAFE NSW, 2004.
Copyright of this material is reserved to Community Services, Health, Tourism and Recreation
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without the written authority of Community Services, Health, Tourism and Recreation Curriculum
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ISBN 0 7348 1589-1
© 2004, TAFE NSW
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3064-8/HLSP Certificate IV in Audiometry - Equipment V1
3064-8/HLSP Certificate IV in Audiometry - Equipment V1
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RESOURCE EVALUATION FORM
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3064-8/HLSP Certificate IV in Audiometry - Equipment V1
3064-8/HLSP Certificate IV in Audiometry - Equipment V1
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TABLE OF CONTENTS
GENERAL INTRODUCTION TO THIS LEARNING RESOURCE ........................... 7
MODULE OVERVIEW ........................................................................................................... 7
MODULE LEARNING OUTCOMES......................................................................................... 8
MODULE ORGANIZATION ................................................................................................... 8
LEARNING OUTCOME 1 ....................................................................................................... 9
CHECKING AND MAINTAINING AUDIOMETRIC EQUIPMENT AUDIOMETER ................................................................................................................. 11
PRACTICAL – 1 HOUR ........................................................................................................ 20
LEARNING OUTCOME 2 ..................................................................................................... 21
MAINTENANCE AND CALIBRATION OF THE TYMPANOMETER ................... 23
SUMMARY ........................................................................................................................ 27
PRACTICAL – 1 HOUR ........................................................................................................ 28
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3064-8/HLSP Certificate IV in Audiometry - Equipment V1
3064-8/HLSP Certificate IV in Audiometry - Equipment V1
7
GENERAL INTRODUCTION TO THIS LEARNING
RESOURCE
This learning resource introduces some of the equipment you may use when performing
clinical hearing assessment. This is one of the recurring themes in the audiometry units of
competency that are aligned to the Certificate IV in Audiometry HLT41302, which is a
qualification of the Health Training Package HLT02. The units of competency that include
the theme of Equipment are;
HLTAU1A - Conduct screening hearing tests for children
HLTAU2A - Conduct screening hearing tests for adults
HLTAU3A – Conduct hearing assessment
HLTAU4A – Dispense hearing devices
Equipment is part of the required knowledge that underpins the development of
competence. Some equipment is fundamental to the audiometry clinic, some items are
optional. The type of equipment you will be regularly using will depend on the situation in
which you will be performing audiometry. It is worthwhile to have some knowledge of the
more widely used apparatus.
Whilst using this learning resource it may also be necessary for you to access resources at
your TAFE college or library. These resources may include computer facilities and
software, library material and videos. The resources are listed under the heading Suggested
Learning Resources for this learning resource.
This learning resource is designed to complement your class or individual learning
activities. You should use this resource as a guide to identify areas of learning.
Module Overview
The purpose of this module is to provide you with basic knowledge about the
type of equipment you will come in contact with as you progress to the practicum
elements of this course. By understanding basic maintenance procedures and implementing
routine equipment checks, the clinician helps ensure the validity of the test results. In this
module the two most fundamental pieces of equipment are discussed however, it is worth
noting that there are a significant number of other types of equipment peculiar to specific
clinical situations. Each of the two learning outcomes will relate to a specific piece of
equipment and at the end of each section there will be some assessment of the student’s
competence.
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Module Learning Outcomes
At the end of this module you will be able to;

Perform biological calibration of an audiometer.

Examine audiometer for faults.

Assess and implement strategies to correct equipment failure.

Perform biological calibration of a tympanometer.

Examine tympanometer for faults.

Implement strategies to correct equipment failure.
Module Organization
There are two learning outcomes for the module, Equipment. Each learning outcome
addresses a different item of basic equipment that the student needs to know about in order
to perform clinical audiometric assessment with surety. The contents are grouped into the
following topics;
Learning Outcome 1
Check and maintain audiometric equipment - Audiometer
Learning Outcome 2
Biological calibration and maintenance of the Tympanometer
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3064-8/HLSP Certificate IV in Audiometry - Equipment V1
Learning outcome 1
Check and maintain audiometric equipment - Audiometer
Assessment criteria:
You will have achieved this learning outcome when you can;

Perform biological calibration of an audiometer.

Examine audiometer for faults.

Assess and implement strategies to correct equipment failure.
To complete this topic you will need
Access to an audiometry laboratory or equivalent clinical environment to complete the
practical component.
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CHECKING AND MAINTAINING AUDIOMETRIC
EQUIPMENT - AUDIOMETER
Recommended Time - 5 hrs
Introduction
Maintaining test equipment is essential if the reliability and validity of test results is to be
ensured. Usually a technician will repair any faults with equipment however the clinician
plays a major role in ensuring the maintenance and daily care of clinical apparatus.
What is an audiometer?
This piece of equipment has been discussed from time to time - just exactly what is
an audiometer? We know it is an instrument for assessing a person’s hearing levels. Most
audiometers can be used to test via air conduction and bone conduction methods. Some
audiometers have functions for testing speech discrimination and reception levels. Some
can be set to administer hearing assessment automatically as well as manually.
An audiometer consists of an audio oscillator which enables the instrument to generate
pure tones at different frequencies, (usually between 250Hz to 8000Hz). An amplifier is
also included to allow variation in the loudness levels for each tone presented. Most
audiometers range in amplitude from -10dB to 110dB.
On the audiometer you will have noticed the decibel (or amplitude) control and the
frequency control. There will also be an on-off switch, usually on the side or back section
of the audiometer and an interrupter (or tone presenter) switch. These controls are on all
audiometers and, apart from these basic functions; audiometers will vary from model to
model.
For those audiometers whose amplitude range is not as high as 110dB, there may be an
output switch that, when activated, allows an additional increase in amplitude of 10 - 20dB
if required. Some interrupter switches have the ability to present the tone in a ‘pulsed
tone’, (warble), as well as a single tone burst. If the audiometer has the functionality to test
both air and bone conduction there will be a switch or button enabling the clinician to
change between either modes of testing. A single channel audiometer has a switch to
change the test ear from left side to right.
Diagnostic audiometers will have ‘masking noise’ available, so there will be an attenuator
to activate the masking noise and vary the level of presentation. On some audiometers the
switch marked ‘reverse’ will need to be turned on for the masking noise to be heard
continuously in the non-test ear. This same switch may be used with speech audiometry.
Some audiometers have a microphone allowing you to speak to the client through the
earphones. There will be a ‘talk over’ or ‘talk forward’ switch which, when pressed, will
activate the ‘talk forward’ microphone. A VU meter will be present on machines with
speech audiometry facilities. This is a glass cased needle meter which tracks the volume of
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the speech presentation, (pre-recorded tape, CD, or by using live voice) through the
microphone to the client.
A panel light display may be present on some audiometers. Usually a light will indicate
when a tone is being presented (this will pulsate with a pulsed tone presentation). When the
client response button is pressed a light will appear on the audiometer for each response
made by the client. If the ‘reverse’ button is activated, a red continuous light will be
activated until it is cancelled by the operator.
Some audiometers may have only the basic functions and some may have more than are
mentioned. Becoming familiar with all the controls on available equipment is important.
This allows the clinician to achieve accurate test outcomes using the most appropriate
types of tests required.
Definition of calibration
The Macquarie Dictionary describes the word calibrate as “to check the accuracy of any
instrument”. Calibration therefore is described as “the act or process of calibrating”. In
Martin’s “Introduction to Audiology” calibration is explained as “The electro-acoustic or
psycho-acoustic determination that an audiometer is performing properly in terms of its
acoustic output, attenuator linearity, frequency accuracy, harmonic distortion, and so on.”
(Martin, 1997: 108). So when we send off an audiometer for calibration, the technician
will be checking the accuracy of the machine and judging this accuracy against a
previously defined standard. In most cases, for Australian audiometry, this standard will
be the International Standard Organisation (ISO).
The audiometer is used to test hearing thresholds in the measure known as Hearing Level
(HL) or Hearing Threshold Level (HTL). The letters HL or HTL will often be seen on the
decibel dial of the audiometer.
Do you remember the curve showing audiometric zero? This curve represents the average
sensitivity of normally hearing adults to the frequencies shown on the audiogram. This
curve is represented by 0dB on the audiogram and is called HL or HTL.
The aim of calibration is to set the audiometer at the level that is audiometric zero for each
frequency.
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3064-8/HLSP Certificate IV in Audiometry - Equipment V1
Activity 1.1
Define dBHTL (dBHL) and state the comparison between dBHTL and dBSPL.
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The comparison between dBHTL and dBSPL is as follows:
Frequency
250Hz
500Hz
1000Hz
2000Hz
4000Hz
8000Hz
Decibels HTL
Decibels SPL
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Comments on Activity 1.1
When we test an individual’s hearing we relate the measure of intensity needed to dBHTL
or dBHL. These terms are synonymous and represent, Decibels Hearing Threshold Level
or Decibels Hearing Level. These are in turn related to dBSPL Decibels Sound Pressure
Level.
Decibels Hearing Threshold Level is the amount of sound in dBSPL that is needed by a
majority of young people with no history of hearing problems (otologically normal) to only
just hear a presentation tone at a particular frequency. That level of dBSPL becomes
0dBHTL, which is called audiometric zero. For example, at 1000Hz the majority needed
7.5dBSPL to just hear that sound, so at 1000Hz 0dBHTL=7.5dBSPL.
On average we need more pressure/intensity to hear the lower frequencies and the higher
frequencies. In other words, our ears are more sensitive at the mid range. So the
comparison between dBHTL and dBSPL is as follows;
Frequency
250Hz
500Hz
1000Hz
2000Hz
4000Hz
8000Hz
Decibels HTL
0
0
0
0
0
0
Decibels SPL
26.5
13.5
7.5
11.0
10.5
13.0
The steps for biological calibration
A technician is able to calibrate the audiometer to ISO standards whenever it is sent for this
service. There are some things the clinician can do on a regular basis to ensure the good
working condition of the audiometer.
When setting up the audiometer each day some standard practices need be observed.
Clean the headphones with appropriate wipes and ensure all leads are plugged into the
correct place on the patch plate and/or directly into the audiometer. Ensure the tones can be
heard through the earphones and bone conductor with the correct correlation.
In an earlier unit the AS/NZS 1269 Standards for workplace audiometry were discussed
including what is required for a ‘daily listening check’ of the audiometer.
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3064-8/HLSP Certificate IV in Audiometry - Equipment V1
Activity 1.2
Describe the steps that might be included in a ‘daily listening check’ (or ‘biological
calibration’).
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Comments on Activity 1.2
The steps involved in a full daily listening check are;

Checking earphone cushions for hardened rubber or cracks.
This involves inspecting the cushions on the earphones and feeling them for cracks and
hardness. If the cushions are not in good condition, extra ambient noise may seep in
through the earphones

Checking the tension of the headband for the earphones and that all leads are
untangled and straightened.
If the headband on the earphones is too loose ambient noise may seep in, or if the band
is too tight the testing will be very uncomfortable for the client. When leads are
tangled potential problems may occur with the tones being sent through to the
headphones. There is a risk of creating an unprofessional appearance if the audiometric
equipment is untidy.

Checking for loose dials and/or clicks when turning the dials on the audiometer.
When turning the dials or pressing the buttons on the audiometer, no sound, except the
pure tone being presented, should be passed through to the earphones. If clicks can be
heard from the dials by the client, this could give clues as to when the tones are being
presented resulting in an unreliable test.

Checking that the sound through the earphones is free of static or noise due to
faulty leads. Turn the attenuator dial to 40 dB at 1000 Hz and listen to the tone
while twisting the leads of each earphone separately.
Having static in the earphones can indicate a fault in the audiometer and will be
disturbing for the client when being tested. They may be confused as to what noise
they are meant to be listening for and respond to sounds other than pure tones.

Checking for gross linearity at 1000 Hz by setting the attenuator at 10 dB and
then increasing it in 10 dB steps up to 90 dB. Listener should check that the
increases in loudness are roughly equivalent from one 10 dB increment to the
next. This should be done for each earphone.
If the decibel level does not increase in loudness in even steps there is a fault with the
audiometer and it should be serviced immediately. Any testing with an audiometer that
has gross linearity problems will be unreliable.

Checking for 'cross-talk'. This is done by positioning one only earphone up to the
ear and presenting a tone through the OTHER earphone. No sound should be
heard in the one held to the ear. Repeat procedure for opposite earphone.
If sound is leaking from one earphone to the other, the clinician cannot be sure which
ear is actually being tested. If this fault is detected, arrangements for the audiometer to
be repaired must be made immediately.
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
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Subjective calibration check established by assessing the tester’s own thresholds.
The clinician need have their own hearing checked regularly and know what the levels
are. A daily listening check to ensure the audiometer is within 10dB of normal levels at
every frequency is standard practice. If the subjective test fails these criteria the
audiometer cannot be used and must be sent off for calibration and repair.
Activity 1.3
Look at the audiometer you have access to in your clinical practise placement. The controls
and functions should be more familiar now. Answer the following questions;
1. What is the dB limit at 1000Hz for air conduction on the audiometer?
2. What is the dB limit at 500Hz for bone conduction on the audiometer?
3. How many channels does the audiometer have?
4. What is a ‘pulsed tone’ used for?
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Maintenance of equipment
Carrying out biological calibration on the audiometer goes a long way in ensuring its good
working condition. However other important factors must be taken into consideration.
Yearly calibration is vital for reliable and valid results to be attained while testing. In fact
if a test is carried out on a machine that is out of calibration date, the results CANNOT be
accepted. This is particularly important if carrying out any audiometry for compensation
or pre-placement medicals.
When a machine is sent for calibration it must be packaged securely, with all leads,
earphones and bone conductor pieces included. Wrap each piece of equipment in bubble
wrap or foam and pack in a box if the audiometer does not have its own padded travel case.
The box must then be marked ‘HANDLE WITH CARE’ or ‘FRAGILE’. If transporting
the machine to the technician personally place the box in the car and secure it with a
seatbelt.
When the audiometer returns from the calibration centre, check all the pieces have been
returned with it. Included with the machine should be a calibration certificate outlining all
the frequencies checked and a calibration sticker indicating the next due date for
calibration.
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It is important to remember when caring for the audiometer and ensuring its reliability to
always keep the same earphones and bone conductor with the audiometer. It may be
tempting to swap earphones and bone conductors between machines in a clinic where a
number of audiometers are available - especially if a fault is found. This is not allowable.
Each machine is calibrated to the earphones and bone conductor that come with it. The
audiometer cannot therefore be used with a different set unless it is recalibrated for that set.
Under no circumstances swap sets as results will be invalid.
Activity 1.4
If possible, visit a centre where audiometers are calibrated and obtain permission to watch
the calibration process. Note how the technician checks for faults and what they are
looking for when calibrating each frequency.
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Equipment failure and detecting faults
Sometimes during testing, it may become apparent that all is not right with the audiometer.
Even if a listening check has been carried out prior to the day’s testing, problems may
occur or something may have been missed in the checking procedure.
How will a fault during testing be detected? The fault may or may not be very obvious.
For example, the client may say “I’m not hearing any tones in my left ear” or they may
simply not be responding to presentation sounds that may otherwise have been expected to
be heard reasonably easily. If this happens you must stop the test immediately and check
the machine.
How should the audiometer be checked at this point?
Follow the steps listed below;
1. Check all leads are pushed into their sockets properly – they may have been knocked
out during testing.
2. Check the leads for kinks – straighten them if any are found.
3. Put the earphones on and present the tones – can anything be heard?
4. Keep listening to the tones and twist the leads to try and detect any static or intermittent
fault.
5. If no fault can be found, re-instruct the client and replace the earphones carefully.
Remember the fault may not be with the machine, it may be with the client or the
tester. Is the client motivated to do the test correctly? Does the clinician know what
they are doing?
6. If a fault is found the testing must be stopped and the machine sent for repair – stating
the problem detected.
If one earphone is working correctly, testing may continue but the earphones will need
to be rotated when changing ears. This is not an ideal procedure but can be used in
emergencies.
Sometimes a fault is not detected until after testing has been completed. What do we mean
by this? How can a fault be detected after the test has finished?
When a number of tests have been completed during the day and the results are being
reviewed prior to report writing, it may be noticed that all left ears have an unusual loss at
2000Hz or that all bone conduction results are unusually good at all frequencies.
When this sort of pattern is discovered, check the audiometer by doing a biological selfcalibration. If a fault is found the audiometer will need to be sent for repair. Most
importantly however, is the validity of the tests carried out that day. These clients must be
re-tested when the audiometer has been repaired. If they are not re-tested their results are
invalid.
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Practical – 1 hour
There is one hour allocated to the practical component for the topic of checking and
maintaining audiometric equipment – audiometer. Arrangements may need to be
confirmed with the teacher.
The practical component involves practising biological calibration of an audiometer.
Check Your Progress Self
Evaluation Questions
Question 1:
When a technician ‘calibrates’ the audiometer, what are they trying to do?
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Question 2:
Explain how to check for ‘cross-talk’.
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Question 3:
What should be done if a fault is detected during testing?
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3064-8/HLSP Certificate IV in Audiometry - Equipment V1
Learning outcome 2
Check and maintain audiometric equipment - Tympanometer
Assessment Criteria:
You will have achieved this learning outcome when you can;

Perform biological calibration of a tympanometer.

Examine tympanometer for faults.

Implement strategies to correct equipment failure.
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MAINTENANCE AND CALIBRATION OF THE
TYMPANOMETER
Recommended Time - 3 hrs
Introduction
As part a routine check of equipment, the tympanometer should also be calibrated
biologically. This is a quick way of establishing whether the tympanometer is in good
working order. A biological calibration means that rather than basing the readings on a set
of data produced by another machine, it is based on the particular result gained from a
person. Therefore a biological calibration should always be done by the same person.
Essentially it means performing a self- test once a week and checking that the results are
not different to the previous week’s results (providing of course that they were normal to
start with).
What is a tympanometer?
A tympanometer measures the ‘compliance’ or ‘admittance’ of the tympanic membrane
while different pressures are being applied to the external ear canal. A probe is inserted
into the ear canal and emits a sound signal under different pressure conditions. The
tympanometer measures the sound energy signal reflected by the tympanic membrane
when these different pressures are applied.
Four basic measurements are made using the tympanometer or acoustic impedance
machine.
1.
Static acoustic compliance measures the mobility of the tympanic membrane
when a particular value of air pressure is applied to the external ear canal.
2.
Tympanometry is a measurement of the middle ear pressure and is determined
by the mobility of the tympanic membrane when various amounts of positive
and negative pressure are applied to the external ear canal. Particularly useful
for determining the condition of the Eustachian tube functionality.
3.
Volume is a measurement of the external auditory canal and varies from
approximately 0.5cc in young children to 1.5cc in adults. The volume of the ear
canal may appear higher in the presence of a perforation of the tympanic
membrane.
4.
Acoustic reflex measures the contraction of the middle ear muscles in response
to intense sounds being introduced to the external ear canal. As the muscles
contract, the middle ear system stiffens decreasing its static acoustic
compliance.
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Conducting biological calibration
To conduct a biological calibration, the same size probe should be used each time. This
helps to keep the volume differences to a minimum (the volume will be dependant on what
depth the probe is inserted into the canal). Run a sweep and calculate the height of the
curve. It should be the same each time. Reflexes should also be present at the same levels
each time the self- test is conducted. Listen to the test tones. Feel the pressure changing,
check that the volume is consistent.
The types of faults that may be expected are;
1.
No pressure change – check pressure tube for cerumen blockage or leak
2.
Sound is too soft, unclear or absent – check for cerumen blockage
3.
Reflex tones are absent – check headphone cables
In order to avoid moisture entering the tubes ensure that all parts are dry before usage. A
common way for moisture to enter the tube is if probe tips are sterilised by using an
alcohol wipe, or using a probe tip which is still wet from sterilisation solution. If a wet tip
is used, the moisture will be sucked up into the tube when the pressure is decreased.
Cerumen is the other common blockage. If possible, request that the clients attend their GP
to have any residual cerumen removed prior to their first appointment for hearing
assessment. Clear auditory canals will benefit all aspects of audiometric assessment.
It is useful to keep spare tubing in the clinic so that it can be replaced if it is leaking or too
blocked. Most tympanometers will be supplied with some type of cleaning implement.
Other faults may be avoided by looking after the cables and interface connections of the
set, (no winding cables around the base or head piece), keeping spare cables and a
sufficient supply of probe tips in an assortment of sizes. Any other faults will have to be
seen to by a qualified technician.
Conducting a self-test once a week is not just good for checking that the equipment is
working appropriately it also provides practise for those students who do not routinely
perform tympanometry. Some people do not readily tolerate the variation of air pressure in
their ears and others find the loud beeps used for registering the acoustic reflexes quite
uncomfortable. By conducting the self-test, it should serve to remind the student to explain
exactly what the test feels like and what to expect. The clients will be more at ease.
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Activity 2.1
Conduct a biological calibration of a tympanometer the next three times you are at a clinic
and write down the results. Look for significant differences. Would it make a difference if
you had a head cold one week? What might you expect to see?
Comments on Activity 2.1
The results of the biological calibration should be fairly close to identical each time. If you
had a head cold you may see a type ‘C’ tympanogram with normal tympanic compliance
and significant negative middle ear pressure. You may see increased or have absent
acoustic reflexes. If the cold were to cause prolonged negative middle ear pressure, you
might see a type ‘B’ tympanogram with no tympanic compliance and normal middle ear
volume.
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Developed by Community Services, Health, Tourism and Recreation Curriculum Centre
© 2004, TAFE NSW
3064-8/HLSP Certificate IV in Audiometry - Equipment V1
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SUMMARY
This unit has discussed the two basic pieces of audiometric encountered in the clinical
environment. It is worth noting that in the course of clinical practise the student may
encounter a variety of diagnostic equipment.
Otoacoustic emissions record the measurement of the sounds that the human cochlea
produces in the absence of any external stimulus. There are a variety of measurements;
SOAE
Spontaneous otoacoustic emissions
EOAE
Evoked otoacoustic emissions
TEOAE
Transient-evoked otoacoustic emissions
Auditory evoked potentials are measured using a test known as electrocochleography,
(ECoG). When acoustic stimuli reach the inner ear a neuroelectric event is triggered and
transmitted along the auditory nerve to the brain. Because hearing is a function of the brain
this test was developed to measure the changes produced in the electrical activity of the
brain.
Auditory brainstem responses (ABR) audiometry measures responses from the brain. A
series of electrodes are placed on the mastoid process behind the client’s ear and a battery
of clicks is presented producing a wave form response.
Real Ear Measurement (REM) machine is designed to make objective measurements of
human ear resonance with and without a hearing instrument in place. This device also has a
built in test box to assist in the verification of hearing instrument settings.
Developed by Community Services, Health, Tourism and Recreation Curriculum Centre
© 2004, TAFE NSW
28
3064-8/HLSP Certificate IV in Audiometry - Equipment V1
Practical – 1 hour
There is one hour allocated to the practical component for the topic of checking and
maintaining audiometric equipment – tympanometer. Arrangements may need to be
confirmed with the teacher.
The practical component involves practising biological calibration of a tympanometer.
Developed by Community Services, Health, Tourism and Recreation Curriculum Centre
© 2004, TAFE NSW