otometrics Madsen AccuScreen PRO User manual

AccuScreen PRO
Otoacoustic Emissions and Automated
ABR Screener
User Manual
Doc no. 7-26-6810/08
Part no. 7-26-68100
0124 1275

FM template version: 01-02-2010
Copyright notice
No part of this Manual or program may be reproduced, stored in a retrieval system, or transmitted, in any form
or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written con-
sent of GN Otometrics A/S.
Copyright©2011, GN Otometrics A/S
Printed in Denmark by GN Otometrics A/S, Denmark
All information, illustrations, and specifications in this manual are based on the latest product information
available at the time of publication. GN Otometrics A/S reserves the right to make changes at any time with-
out notice.
Warranty/Disclaimer
The warranty of GN Otometrics A/S and the manufacturer, Fischer-Zoth Diagnosesysteme GmbH/ Natus Eu-
rope GmbH with regard to operation, quality or functionality of the AccuScreen does not apply if:
• The equipment is not installed and used in accordance with the instructions in the manual.
• Installation, assembly, extensions, readjustments, modifications, service and repair are performed by per-
sonnel other than those authorized by GN Otometrics.
• The electrical installation of the equipment is not connected to earth and does not comply with IEC require-
ments.
Version release date
8. September 2011
Technical support
Please contact your supplier.
GN Otometrics A/S
9 Hoerskaetten
DK-2630 Taastrup Denmark
T: [phone], F: [phone]
www.otometrics.com

GN Otometrics A/S 3
Contents
1 Introduction
1.1 The AccuScreen PRO .................................................................................................................. 9
1.1.1 Intended Use .................................................................................................................. 10
1.1.2 AccuLink ......................................................................................................................... 10
1.2 About this manual ....................................................................................................................... 10
1.3 New Features ............................................................................................................................. 11
1.4 Typographical conventions ......................................................................................................... 11
2 Test Methods
2.1 About Otoacoustic Emissions ..................................................................................................... 13
2.1.1 Recording OAEs.............................................................................................................13
2.1.2 Types of OAEs ............................................................................................................... 14
2.1.3 Applications of OAEs...................................................................................................... 15
2.1.4 How the AccuScreen PRO T-module determines a PASS............................................. 15
2.1.5 How the AccuScreen PRO D-module determines a PASS ............................................ 16
2.2 About Auditory Brainstem Response (ABR) ............................................................................... 17
2.2.1 How the AccuScreen PRO A-module determines a PASS ............................................ 18
2.2.2 Advantages of combined OAE/ABR-Screening.............................................................. 19
2.3 The different versions of the AccuScreen PRO .......................................................................... 19
3 The AccuScreen PRO
3.1 Front view ................................................................................................................................... 21
3.2 Top view ..................................................................................................................................... 22
3.3 Bottom view ................................................................................................................................ 22
3.4 Reverse side view....................................................................................................................... 23
3.5 Display & control panel ............................................................................................................... 24
3.6 Ear probe .................................................................................................................................... 25
4 Before You Start
4.1 Safety.......................................................................................................................................... 27

User Manual AccuScreen PRO
4GN Otometrics A/S
4.2 Unpacking the AccuScreen PRO................................................................................................ 27
4.3 Operating temperature................................................................................................................ 28
4.4 Storing the AccuScreen PRO ..................................................................................................... 28
4.5 Battery ........................................................................................................................................ 28
4.5.1 Battery test ..................................................................................................................... 28
4.5.2 Removing and recharging the battery ............................................................................ 29
4.5.3 The charger .................................................................................................................... 30
4.5.4 Battery safety information............................................................................................... 30
4.5.5 Increasing service life ..................................................................................................... 31
4.5.6 Environmental Protection ............................................................................................... 31
4.6 Data/printer interface .................................................................................................................. 31
5 Preparing for testing
5.1 Connecting the probe ................................................................................................................. 33
5.2 Connecting the electrode cable for ABR testing ......................................................................... 33
5.3 Connecting the Y-cable for ABR testing ..................................................................................... 33
5.4 Preparing the test environment................................................................................................... 34
5.5 Preparing the patient .................................................................................................................. 34
5.5.1 Placing electrodes for ABR testing ................................................................................. 35
5.5.2 Fitting the eartip on the probe......................................................................................... 36
5.5.3 Fitting the Ear Couplers.................................................................................................. 36
5.6 Preparing the AccuScreen PRO .................................................................................................38
6 Tests
6.1 Test methods .............................................................................................................................. 41
6.1.1 Test process TEOAE...................................................................................................... 41
6.1.2 Test process DPOAE ..................................................................................................... 42
6.1.3 Test process DPOAE Diagnostic.................................................................................... 45
6.1.4 Test process ABR...........................................................................................................47
6.2 Monitoring the test ...................................................................................................................... 50
6.2.1 TEOAE tests................................................................................................................... 50
6.2.2 DPOAE tests .................................................................................................................. 51
6.2.3 DPOAE Diagnostic tests................................................................................................. 52
6.2.4 ABR tests........................................................................................................................ 53
6.3 After the test ............................................................................................................................... 53
6.3.1 Adding comments to a test ............................................................................................. 53
6.4 Interpretation of the results ......................................................................................................... 54
6.4.1 TEOAE ........................................................................................................................... 54

AccuScreen PRO User Manual
GN Otometrics A/S 5
6.4.2 DPOAE ........................................................................................................................... 56
6.4.3 ABR ................................................................................................................................ 56
7 Quick Test
7.1 Performing a Quick Test ............................................................................................................. 59
8Printing
8.1 The "Print results" menu ............................................................................................................. 61
8.1.1 Types of printout............................................................................................................. 62
9 View Results
9.1 Viewing test data ........................................................................................................................ 65
10 The Transfer/Delete Data Menu
10.1 Data transfer ............................................................................................................................... 67
10.1.1 Transfer via cable ........................................................................................................... 67
10.1.2 Transfer via infrared ....................................................................................................... 68
10.2 Delete data ................................................................................................................................. 68
11 Options
11.1 Self Test...................................................................................................................................... 71
11.1.1 Probe test ....................................................................................................................... 72
11.1.2 Discharge battery ........................................................................................................... 73
11.1.3 Codec test ...................................................................................................................... 73
11.1.4 LCD display test ............................................................................................................. 73
11.1.5 Keyboard test ................................................................................................................. 73
11.2 Settings 1.................................................................................................................................... 74
11.2.1 Language........................................................................................................................ 74
11.2.2 Date/Time ....................................................................................................................... 75
11.2.3 Date/Time format............................................................................................................ 75
11.2.4 Background Lighting (Display)........................................................................................ 75
11.2.5 Sounds ........................................................................................................................... 75
11.2.6 Default test ..................................................................................................................... 76
11.3 Settings 2.................................................................................................................................... 76

User Manual AccuScreen PRO
6GN Otometrics A/S
11.3.1 User login ....................................................................................................................... 77
11.3.2 Patient list mode ............................................................................................................. 77
11.4 ABR configuration....................................................................................................................... 78
11.4.1 Notch filter setting........................................................................................................... 78
11.4.2 ABR stimulus level setting .............................................................................................. 79
11.5 Memory Used ............................................................................................................................. 79
11.6 Version information..................................................................................................................... 80
12 Maintenance
12.1 Probe cleaning and maintenance ............................................................................................... 81
12.1.1 Cleaning and disinfecting the probe tip .......................................................................... 81
12.1.2 Changing the acoustic filter disc..................................................................................... 83
12.1.3 Eartips ............................................................................................................................ 83
12.1.4 Cleaning and disinfecting procedures ............................................................................ 83
12.1.5 Cleaning and disinfecting the test cavity ........................................................................ 84
12.2 Cleaning the Y-cable .................................................................................................................. 84
12.3 Battery maintenance................................................................................................................... 84
12.3.1 Safety information........................................................................................................... 84
12.3.2 Increasing service life ..................................................................................................... 85
12.3.3 Environmental protection................................................................................................ 85
12.4 Cleaning the AccuScreen PRO .................................................................................................. 85
13 Safety Information
13.1 Safety.......................................................................................................................................... 87
13.1.1 Safety Symbols............................................................................................................... 87
13.2 Warranty ..................................................................................................................................... 87
13.3 Repair, after-sales service and regular checks........................................................................... 88
13.3.1 Declaration ..................................................................................................................... 88
13.3.2 Service and repair .......................................................................................................... 88
14 Status and error Messages
15 Technical Specifications
15.1 Device......................................................................................................................................... 91
15.2 Battery and charger .................................................................................................................... 91
15.3 Probe .......................................................................................................................................... 92

AccuScreen PRO User Manual
GN Otometrics A/S 7
15.4 Measurement techniques ........................................................................................................... 92
15.5 Device class................................................................................................................................ 93
15.6 Applied standards ....................................................................................................................... 93
15.7 Manufacturer............................................................................................................................... 94
15.8 Distributor ................................................................................................................................... 94
16 Index

User Manual AccuScreen PRO
8GN Otometrics A/S

AccuScreen PRO User Manual Introduction
GN Otometrics A/S 9
1 Introduction
Thank you for purchasing the AccuScreen PRO handheld Otoacous-
tic Emissions and Automated ABR Screener.
This manual is your guide to the use and maintenance of your
AccuScreen PRO.
We strongly recommend that you read it carefully through before
using your AccuScreen PRO for the first time.
We also recommend that you take particular note of the cleaning and
maintenance instructions. Failure to use and maintain the Accu-
Screen PRO correctly may void your warranty.
1.1 The AccuScreen PRO
The AccuScreen PRO is a fast, reliable, easy to use, and lightweight
hearing screener, optimised for neonatal screening. The AccuScreen
PRO closes the gap between electrophysiological assessment, which
is time-consuming and expensive, and behavioural observation.
The AccuScreen PRO uses TEOAE (Transiently Evoked Otoacoustic
Emissions) and DPOAE (Distortion Product Otoacoustic Emissions)
technologies, which are highly effective for neonatal hearing screen-
ing. Otoacoustic Emissions measure cochlear mechanics and indi-
cate whether the cochlea is functioning correctly or not. Children's
emissions are typically strong, which makes them easy and fast to
detect. Emission strength usually decreases with age.
Automated ABR (Auditory Brainstem Response) is also available in
the AccuScreen PRO. This technology measures responses to sound
in the auditory pathways. It provides a valuable supplement to TE-
OAE and DPOAE screening, and is an essential tool for screening of
infants at risk of hearing loss.
The simple, yet reliable technology ensures that hearing loss can be
detected, and intervention can be implemented, at an early age.
With early intervention, hearing-impaired children are given the
possibility of developing normal speech and language skills.

10 GN Otometrics A/S
Introduction AccuScreen PRO User Manual
1.1.1 Intended Use
The AccuScreen PRO TEOAE is optimised for use with neonates and
the paediatric population, while DPOAE test is appropriate for all
patients. The AccuScreen PRO probe is extremely lightweight (only
4 grams), and comes with comfortable, easy to insert probe tips. This
makes it ideal for use with infants and children, as well as older pa-
tients.
The TEOAE tests are directed at children less than 6 years of age. The
ABR and DP tests are directed at all age groups.
Important:
GN Otometrics A/S does not guarantee the accuracy of the test re-
sults or the tests themselves, if other accessories than those supplied
by GN Otometrics A/S are used for this device (i.e. eartips, elec-
trodes, Ear Couplers, etc.).
1.1.2 AccuLink
For details concerning the AccuLink software please see AccuHelp
in the AccuLink software.
1.2 About this manual
Important:
Please note that menu selections and screen shots in this manual
may not reflect the configuration of your test device.
This manual contains a description of the main functions of the Ac-
cuScreen PRO. GN Otometrics A/S recommends that you make
yourself familiar with the following issues:
Installation
Section 4.2, ‘Unpacking the AccuScreen PRO” on page 27, Chapter
3, “The AccuScreen PRO” on page 21, and Chapter 5, “Preparing for
testing” on page 33 contain a full description of unpacking instruc-
tions, controls and socket connections, and how to install the device.
Safety
This User Manual contains information and warnings which must
be followed to ensure the safe performance of the AccuScreen PRO.
Local government rules and regulations, if applicable, should also
be followed at all times.
Please see the overview of device labelling in Chapter 3, “The Accu-
Screen PRO” on page 21 and read the warning notes in Chapter 13,
“Safety Information” on page 87.

GN Otometrics A/S 11
AccuScreen PRO User Manual Introduction
Training
It is recommended that you read this manual before you start oper-
ating the AccuScreen PRO so that you become familiar with the de-
vice before testing on a client.
Maintenance and cleaning
For instructions on how and when to clean the AccuScreen PRO,
please see Chapter 12, “Maintenance” on page 81.
1.3 New Features
The AccuScreen PRO provides a feature for setting the stimulus lev-
el at either 35, 40 or 45 dB nHL. The stimulus level can be preset ei-
ther from the Options menu, or by the user being prompted to select
the level before every ABR test (see how to select the stimulus level
in Section 11.4.1, ‘Notch filter setting” on page 78.)
1.4 Typographical conventions
The use of WARNING, CAUTION and NOTE
For safety reasons and appropriate use of the AccuScreen PRO, the
manual contains WARNINGS, Cautions and Notes, which you
should read carefully. They are used as follows:
WARNING:
A warning indicates that there is a risk of danger to persons and de-
vice.
Caution:
A caution indicates that there is risk of damage to the device.
Note:
A note indicates that you should take special notice.

12 GN Otometrics A/S
Introduction AccuScreen PRO User Manual

AccuScreen PRO User Manual Test Methods
GN Otometrics A/S 13
2 Test Methods
2.1 About Otoacoustic Emissions
Congenital hearing impairment has serious consequences for
speech and language acquisition as well as emotional and intellectu-
al development. Recent research has confirmed that this can be min-
imised, when identification and intervention occur, before the
hearing-impaired child reaches 6 months of age. In addition, techno-
logical advances have made automated screening of infants' hearing
possible by a wide range of caregivers. One such automated screen-
ing method makes use of the presence of otoacoustic emissions to
determine its outcome.
Otoacoustic emissions (OAEs) are sounds found in the ear canal that
originate from activity in the cochlea. These sounds are small, but
potentially audible, sometimes amounting to as much as 30 dB SPL.
They are created by motion of the eardrum driven by vibrations in
the cochlea, which are transmitted through the middle ear chain.
Consequently, they can be detected only when the middle ear is op-
erating normally. OAEs are generated only when the Organ of Corti
is in normal or near normal condition. They can emerge spontane-
ously, but more commonly follow acoustic stimulation.
Note that otoacoustic emissions do not contribute to hearing, but are
by-products of an active process in the cochlea, in which motility of
the outer hair cells tunes the basilar membrane and amplifies weak
sounds. They are clinically significant in the sense that they provide
an indication of the integrity of the cochlear amplifier/outer hair
cells.
2.1.1 Recording OAEs
In general, the recording of all OAEs requires that a sensitive, low
noise microphone be sealed in the external ear canal. Recording of
emissions elicited by an acoustic stimulus also requires that there is
one (for TEOAE) or two receivers (for DPOAE) to deliver the stimu-
li. The microphone records the sound present in the external ear ca-
nal in response to the acoustic stimulus. The type of signal analysis
used depends on the type of emissions to be recorded.

14 GN Otometrics A/S
Test Methods AccuScreen PRO User Manual
2.1.2 Types of OAEs
Spontaneous otoacoustic emissions (SOAE)
SOAEs are low level, tonal signals, which are measured in the ear ca-
nal in the absence of any known stimulus. They are usually inaudi-
ble to the persons from whose ears they are detected.
SOAEs are of limited use clinically because they cannot be measured
in all ears, and appear at discrete and unpredictable frequencies.
However, the presence of an SOAE indicates that hearing is within
normal limits near the frequency at which it appears. In addition, it
may influence behavioural testing, as well as measurements of other
types of OAEs.
Transiently evoked otoacoustic emissions (TEOAEs)
This type of emission is elicited by brief stimuli such as clicks or tone
bursts. They can be recorded in nearly all persons with normal hear-
ing. When a click is used to elicit the response, the resultant wave-
form is, like a fingerprint, idiosyncratic.
TEOAEs are extremely non-linear. Their pattern of growth is consist-
ent with the operation of the cochlear amplifier, which provides
most gain for low level inputs, and lends support to the notion that
OAEs arise from outer hair cell activity.
TEOAEs do not correlate with behavioural audiometric thresholds.
Consequently, it is not possible to predict hearing thresholds based
on TEOAE thresholds. However, since the presence of TEOAEs cor-
relates strongly with normal hearing, the most common clinical ap-
plication involves click stimulation at moderate intensity levels for
the purpose of hearing screening or differential diagnosis.
Distortion Product Otoacoustic Emissions (DPOAE)
As with other OAEs, DPOAEs are thought to be generated by the ac-
tive cochlear process, which is responsible for enhancing the basilar
membrane motion.
DPOAEs are tones produced by the ear in response to two simulta-
neous pure-tone stimuli known as primary tones. They are "distort-
ed" in the sense that they are not present in the eliciting pure-tone
stimuli. The lower frequency pure-tone stimulus is called the f1 pri-
mary, and the higher frequency stimulus is called the f2 primary.
The most frequently measured distortion product is at the frequency
2f1-f2, although the cochlea also produces distortion products at
other frequencies. The 2f1-f2-distortion product is the largest distor-
tion product, and is the only one utilised for clinical purposes at
present.

GN Otometrics A/S 15
AccuScreen PRO User Manual Test Methods
2.1.3 Applications of OAEs
Identification of hearing loss
The presence of TEOAEs strongly indicates that a portion of the au-
diogram has hearing threshold levels better than 25 dB HL, and cor-
relates best with good hearing in the mid-frequency range. It is not
possible to rely on the TEOAE spectrum to predict threshold levels
by frequency. TEOAEs are well suited and widely accepted for the
purpose of screening hearing.
It has been hoped that DPOAEs would allow clinicians to predict be-
havioural thresholds, but this is not yet the case. However, there is
correspondence between DP-gram configurations and audiogram
configurations (i.e. in ears with sensory hearing loss, DPOAEs are
reduced or eliminated only for the stimulus frequency regions,
which coincide with the impaired region). Accordingly, DPOAEs
can give a better frequency specific impression of cochlear integrity
than TEOAEs, and are well suited to monitoring of cochlear func-
tion.
Differential diagnosis
While OAEs have not proven good predictors of auditory nerve tu-
mors, they nevertheless provide the opportunity to document nor-
mal or near-normal cochlear function. This makes them helpful in
pinpointing sites of lesion, as well as in making management deci-
sions.
2.1.4 How the AccuScreen PRO T-module determines a PASS
Applies to AccuScreen PRO T, TA, TD, TDA.
AccuScreen PRO uses a binomial statistical test to give either a PA S S
or a REFER result. Most TEOAE instruments use the signal-averag-
ing technique with two buffers. In contrast, the AccuScreen PRO cal-
culates the statistical probability that an emission has been recorded
at a succession of sampling points ranging from 6 to 12 ms after the
end of the stimulus.
The AccuScreen PRO processes each of the sampled points individ-
ually. For each point, it is assumed that no time-locked signal (otoa-
coustic emission) is present. If this is true, then the distribution of
positive and negative deflections across sweeps at a point in the
waveform will be normal. Thus, the probability that a time-locked
signal is present can be determined by comparing the distribution of
positive and negative deflections at each data point to a normal dis-
tribution. The criterion level used by the AccuScreen PRO signal de-
tection algorithm for presence of a time-locked signal is 99.7%.
Each recorded sweep is assigned to one of eight quality buffers, ac-
cording to its amplitude. The statistical analysis is carried out simul-
taneously in each quality buffer, and the test result will be a PA S S if

16 GN Otometrics A/S
Test Methods AccuScreen PRO User Manual
the criterion for this outcome is met in any of the quality buffers. A
PA S S is indicated by the presence of 8 data points at which a time-
locked signal has been detected.
The advantage of this system over the usual averaging techniques is
that the tests are more robust with regard to noise and the test dura-
tion can be reduced. Also, the statistical criterion reduces the proba-
bility for a false negative result down to less than 0.1%.
Artifact is defined in the AccuScreen PRO as a sweep which, based
on its relatively large amplitude, is likely to be influenced mostly by
noise. Thus, including it in the analysis would lower the signal-to-
noise ratio and prolong test time. The automatic identification and
exclusion of artifact results in a dramatic shortening of the test dura-
tion, especially in the case of restless infants. An artifact rate, which
exceeds 20%, indicates that conditions are too noisy to carry out re-
liable tests.
The Stimulus Stability indicates the proportion of recorded sweeps
in which the tested stimulus level deviates significantly from the cal-
ibrated level. Low stimulus stability indicates that the probe has
moved during testing.
2.1.5 How the AccuScreen PRO D-module determines a PASS
Applies to AccuScreen PRO D, DA, TD, TDA.
Distortion Products are the result of cochlear activity, which origi-
nates from processing a two-tone signal. The two tones are called
"primaries", and their frequencies are designated as f1and f2, and the
levels are termed L1and L2.
The challenge of DPOAE evaluation is to discriminate environment
sounds - the "noise" - from the cochlear sound response, the Distor-
tion Product (DP). This cannot be achieved with absolute certainty.
However, by applying an appropriate statistical algorithm, the
chances of wrongly classifying noise as a cochlear signal can be re-
duced to a known probability - in the AccuScreen PRO the probabil-
ity of erroneously identifying noise as a DP is 0.3% for each
frequency applied.
Conventional criteria used commonly in DP screening devices are
based on algorithms which attempt to estimate the "noise floor" by
averaging the amplitude of the response at frequencies adjacent to
the DP frequency. This value is then compared to the amplitude of
the response at the DP frequency, and the difference is taken to be
the Signal-to-Noise Ration (SNR). Such methods show a false PA S S
rate that is considerably higher than the AccuScreen method. In fact,
the false PA S S rate can be up to 10% for the commonly used criteria
of 6 dB SNR.

GN Otometrics A/S 17
AccuScreen PRO User Manual Test Methods
The statistical method used by the AccuScreen PRO makes it possi-
ble to evaluate the spectrum specifically at the frequency of the ex-
pected DP. Thus, no comparison with adjacent spectral lines is
necessary.
During a specified time the acoustic activity at the expected DP fre-
quency FDP=2F1-F2is analyzed by reducing the spectral component
to a unit vector. Its phase is determined mathematically. By repeat-
ing this procedure, a set of unit vectors with different phases is ob-
tained. These vectors can be added by using the laws of vector
addition in the polar coordinate system.
The evaluation is based upon the laws of statistical distributions: it
can be shown mathematically that the vector sum of nrandomly dis-
tributed unit vectors will not exceed a certain value with a probabil-
ity 99.7%. Spectral components of random noise with phases that are
independent of the primary tones behave like that. A DP with fixed
phase relative to the phases of the primaries will add a constant val-
ue to the vector sum. Therefore, if the vector sum exceeds this limit,
the presence of an emission can be claimed on a 99.7% confidence
level.
This criterion is set up for each of four frequencies applied: 2 kHz,
2.5 kHz, 3.2 kHz and 4 kHz.
An overall PA S S result requires 3 passes out of 4 frequencies.
The Diagnostic DP facility performs DP testing at two stimulation
levels, which results in 8 measurements (4 frequencies at 2 levels: 1.5
kHz, 2 kHz, 3 kHz and 4 kHz). The statistical analysis described
above is also used for Diagnostic DP. An overall PA S S result requires
6 passes out of the 8 measurements.
2.2 About Auditory Brainstem Response (ABR)
Sounds are processed by the different parts of the ear and trans-
formed by the auditory sensory cells to a series of action potentials,
which are transmitted to the brain by neural conduction. On their
way to the auditory cortex the action potentials pass a number of re-
gions called nuclei, where the coded acoustic information is filtered,
processed, compared to other information, and distributed to differ-
ent pathways. These nuclei are the origin of „bursts" of synchronous
multiple cell discharges, which cause electro-magnetic „far-field po-
tentials", which can be tested via scalp electrodes. The potentials
picked up by the electrodes are called Auditory Evoked Potentials
(AEP) or auditory responses.
There are different AEP-producing regions between the cochlea and
the primary auditory cortex. However, the responses of the brain-

18 GN Otometrics A/S
Test Methods AccuScreen PRO User Manual
stem (ABRs) are particularly well suited for hearing tests in new-
borns, infants and children. Reasons for this include:
• The responses are not influenced by state, and can thus be
tested during sleep. This is the ideal state to test ABRs because
it minimises influence of potentials from muscular activity,
which could make a good measurement difficult.
• Many investigations have shown that the behavioural hearing
threshold correlates strongly with the response threshold of
the brainstem. In other words: If an ABR can be tested as a
response to an acoustic stimulus, it is nearly certain that the
individual can hear this stimulus. It would only be in rare
cases of damage to the midbrain or auditory cortex that this
would not hold true.
Care must be taken during testing and evaluation in order to avoid
false results. The amplitude of the electric response to a 30 or 40 dB
stimulus is frequently below 100 nV and therefore considerably low-
er than the scalp electroencephalogram (EEG) and electromyogram
(EMG).
2.2.1 How the AccuScreen PRO A-module determines a PASS
Applies to AccuScreen PRO A, TA, DA, TDA.
The Auditory Brainstem Response (ABR) is a low-amplitude signal
usually buried in the electric brain and muscle activity (EEG and
EMG). It can only be extracted by applying special filtering tech-
niques. "Averaging" is the procedure most commonly used to make
it visible: the stimulus is presented repeatedly - up to several thou-
sand times - and the signal from the electrodes, which follow the
stimulus, is summed continuously until the response can be detect-
ed.
Visual detection and interpretation of such a signal requires a great
deal of expertise. For screening purposes, the decision to pass or re-
fer must be performed quickly and automatically. As a consequence,
a different evaluation approach must be used for screening.
Like the methods for automatic detection of TEOAE and DPOAE in
the AccuScreen PRO, a statistical approach determines the ABR
PA S S criterion. The basic procedure - application of binomial statis-
tics - is the same as described in Section 2.1.4, ‘How the AccuScreen
PRO T-module determines a PASS” on page 15. Because the shape of
the ABR response waveform changes with age, the detection algo-
rithm is optimised accordingly by pre-filtering the recorded signals
with a typical pattern for infants up to one year old. Although this
does not preclude testing older children and adults with the Accu-
Screen PRO, the sub-optimal fit may result in longer test times for
these patients.

GN Otometrics A/S 19
AccuScreen PRO User Manual Test Methods
2.2.2 Advantages of combined OAE/ABR-Screening
The AccuScreen PRO provides a feature for setting the stimulus lev-
el at either 35 or 45 dB nHL. This means that it is either 35 or 45 dB
above the normal hearing threshold of a healthy individual.
The spectrum of the stimulus includes all frequencies between 500
and 4000 Hz, but due to filtering in the ear canal and other influenc-
es, the main region tested is between 2000 and 4000 Hz. Most signif-
icant hearing losses can be found in this region.
As compared to the testing of otoacoustic emissions, the ABR dis-
criminates more precisely between mild and moderate hearing loss-
es. Consequently, its specificity for detecting moderate losses is
higher. However, the test requires more time for preparation and
testing than an OAE test. Automated ABR tests are therefore ideal as
a second step following an OAE screening test with a REFER result,
as well as screening children who are at greater risk for retrocochlear
hearing loss.
2.3 The different versions of the AccuScreen PRO
The AccuScreen PRO is available as a single-step or multi-step hear-
ing screener. You can choose between the following test methods:
AccuScreen PRO T> TEOAE
AccuScreen PRO D> DPOAE
AccuScreen PRO A> ABR
AccuScreen PRO TD> TEOAE and DPOAE
AccuScreen PRO TA> TEOAE and ABR
AccuScreen PRO DA> DPOAE and ABR
AccuScreen PRO TDA> TEOAE, DPOAE and ABR

20 GN Otometrics A/S
Test Methods AccuScreen PRO User Manual