Assessing Open-Ear Edulink Fittings - Access 2 Conference - Phonak

FM for Children
Chapter 7
Assessing Open-Ear Edulink Fittings
Leisha R. Eiten, M.A.
Leisha Eiten received her M.A. in Audiology from the University
of Iowa and her Au.D. from ATSU through the Arizona School of
Health Sciences. She has been employed as a clinical audiologist
and clinical coordinator at Boys Town National Research Hospital
since 1990. She has presented and published on topics involving
Pediatric Audiology and Amplification and FM System Evaluation
and Fitting. She has served on the AAA Task Force to develop
Pediatric Amplification Guidelines and the AAA Task Force to develop
guidelines for Remote Microphone HAT and the companion
instructional DVD. In addition to these responsibilities, she has
been involved with the development of the “babyhearing.org”
website and other information dissemination activities.

78 Assessing Open-Ear Edulink Fittings
Assessing Open-Ear Edulink Fittings
Leisha R. Eiten, M.A.
The children that we serve today are using
a wide variety of hearing aid and assistive
technologies. Our priority as audiologists
is to provide the best possible intervention
for a child and to make sure the technology
being used is set appropriately for him or
her. A standardized process is needed for
determining device candidacy and verifying
the function of the many types of technologies
available. Remote-microphone
Hearing Assistance Technology (HAT)
guidelines have recently been published
by the American Academy of Audiology
(American Academy of Audiology [AAA],
2008). The purpose of the guidelines is
to standardize the process of candidacy
determination, selection and implementation
of remote microphone devices. Supplements
on verification procedures for the
different types of HAT devices are being
published in addition to the main guidelines.
The first supplement (Supplement A.
“Fitting and Verification Procedures for
Ear-level FM”) has been published with
step-by-step verification procedures specific
to ear-level devices (AAA, 2008).
The guidelines define three main listening
groups as being potential remote-microphone
HAT candidates. They are:
Group 1: Children/Youth with hearing
loss who are current or potential hearing
aid users
Group 2: Children/Youth with Cochlear
Implants
Group 3: Children/Youth with normal
hearing sensitivity who have special
listening needs
Recommended HAT fitting configurations
and additional fitting options are outlined
in the guidelines based on the listener
group. A population that is specifically
addressed in the new guidelines is Group 3:
Children and Youth who have normal
hearing and special listening needs. There
are a wide variety of listening and learning
disorders in this category, including unilateral
or minimal hearing loss, auditory processing
disorders, language-learning delay
or disorders, auditory neuropathy/dyssynchrony
and attention deficit disorders.
Second-language learners may also have
special listening needs and are included in
this listener group.
A common characteristic of this disparate
group is documented evidence of listening
difficulties in adverse acoustic environments.
Listening difficulties for this population
most often occur in high background
noise levels, highly reverberant environments
and when listening from a distance.
These children may also have documented
problems attending in an educational
setting when competing sounds or activities
are present. The remote-microphone
HAT guidelines include instructions for
documentation of listening difficulties and
determining which children would benefit
from a HAT device. Evaluation of word
recognition performance in noise, documentation
of the child’s classroom listening
environment as well as observation and/or
review of the child’s listening performance
in their classroom environment, are all im -
portant for determining if a child would
benefit from remote-microphone assistance.
The remote-microphone HAT
guidelines recommend that audiologists
use tools that provide quantifiable data
and supply information regarding the
child’s performance without the use of the
HAT. In addition, student self-assessment
measures may be used, as well as teacher
and/or parent questionnaires to determine
the child’s emotional status and potential
acceptance of a HAT device in the classroom.
A comprehensive evaluation incorporating
multiple assessments provides a
variety of perspectives of the child’s hearing
and listening performance to assist in
candidacy determination.
A number of other chapters in these
proceedings deal with FM use for children
and adults with auditory neuropathy/dyssynchrony
and auditory processing deficits.
Although unilateral (UHL) and minimal
hearing losses are not discussed in detail
elsewhere in these proceedings, a growing
body of evidence is available about the
listening and learning effects of unilateral
and mild hearing loss (Eichwald & Gabbard,
2008). Children with UHL or minimal loss
are considered candidates for remote-microphone
HAT devices. Particularly when
traditional hearing aid amplification is not
beneficial or acceptable, an HAT option
should be considered.
No specific default arrangement for
remote-microphone HAT is recommended
by the AAA Guidelines for children in
Listener Group 3. FM-only HAT device
options for children with normal hearing
include non-occluding body-worn FM

Leisha R. Eiten
79
systems with headphones or earbuds, personal desk-top and
classroom sound-field devices using infra-red or FM transmission,
and ear-level FM-only devices. The remainder of this chapter will
focus on recommended verification procedures for ear-level FMonly
devices such as the Phonak Edulink TM .
Before detailing the steps of ear-level FM-only device verification,
it is important to review the larger purpose of verification in
general. That is, how should the chosen FM system function and
how should the individual parts of the FM system be verified?
Three priorities should be addressed when verifying an ear-level
FM-only system. First, confirm that the FM system can maintain
comfort and consistent audibility of a close speech input coming
from the FM microphone. Typical FM microphone placements
range from about 1 inch (2.5 cm) with a boom or cheek-level mi -
crophone to approximately 6 inches (15 cm) with a chest-level
lapel or lavalier microphone. With such close distances between
the talker’s mouth and the microphone,
high input levels are expected. The second
priority is to evaluate the maximum output
of the system in the listener’s ear(s). With
ear-level FM-only devices being used pri -
marily on normal or near-normal hearing
ears, verification and control of the maximum
output in the user’s ear is critical. Use
of a high level (85-90 dB SPL) pure-tone swept input is recommended
to confirm sound pressure levels in the child’s ear(s). Changes
in output programming may be required to limit real-ear maximum
output levels from the FM-only device. The third priority is to
confirm that the FM-only system provides benefit in the child’s
listening environments. The first two verification priorities can
be confirmed by performing real-ear electroacoustic evaluation
of the audibility and maximum output from the FM system. The
third priority requires that some type of behavioral verification
be performed, with an emphasis on testing speech perception in
noise.
Two sound pathways
must be considered when
verifying a non-occluding
FM-only fitting: amplified
and unamplified.
Real-Ear Electroacoustic Verification
Why do the current verification guidelines for FM-only systems
such as the Edulink TM recommend real-ear verification rather
than electroacoustic testing in a 2 cc coupler? Testing in a test
chamber rather than in the child’s ear would certainly be more
efficient. However, non-occluding ear-level fittings have special
verification considerations because of the non-occluding coupling
to the ear. The open-ear acoustics must be accounted for in the
verification process. Each person’s ear has unique acoustic properties
when an ear-level FM-only device is in place. Real-ear evaluation
is needed to verify the maximum output and recommended
use-volume of the system for the individual child.
Two sound pathways must be considered when verifying a nonoccluding
FM-only fitting: amplified and unamplified. The first
(amplified) pathway is the input from the main talker or teacher
into the FM microphone that is routed
through the FM receiver and into the user’s
ear. Because the ear is unoccluded, sounds
from this path not only route into the ear
from the receiver, but may also “leak out”
out of the ear canal. This will affect the
low-frequency portions of the FM input
significantly more than the higher-fre quency
portions of the signal. The acoustical effects of the unoccluded
ear canal are well known. In fact, the low-frequency loss of amplified
speech from an unoccluded ear canal is the basis for current
open-ear hearing aid designs for individuals with normal lowfrequency
hearing. The largest effect is typically seen at 1000 Hz
and below. (Mueller & Ricketts, 2006; Hoover, Stelmachowicz &
Lewis, 2000)
The second sound pathway is the unamplified input of sounds
that enter the unoccluded ear canal directly from sources other
than the remote FM microphone. These inputs may include un -
amplified portions of the main talker (teacher’s) voice, other talkers
or students, the child’s own voice and background noises present
in the environment. All unamplified sounds can enter and exit

80 Assessing Open-Ear Edulink Fittings
Figure 1. Test equipment set-up for verification Option 1.
Figure 2. Verification Option 1. Curve 1 (upper curve) represents maximum
output measurement at volume full-on. Curve 2 (vertical hatches) represents
audibility at use-volume.
freely from the unoccluded ear canal. As they are not part of the
amplified pathway, no loss of low frequencies is seen. All unamplified
inputs enter the ear canal together, with individual inputs
at higher or lower intensity levels depending on the sound source,
room acoustics and distance of the source from the student.
It is important to verify the audibility of a variety of unamplified
input levels in relation to the amplified FM signal with the ear-level
FM receiver in place on the student’s ear(s). Because of variations in
ear size and the coupling option used to fit the FM-only receiver
in a child’s ear, the audibility of unamplified inputs will vary. One
of the highest intensity signals present in the ear canal is likely to
be the amplified input from the FM microphone. This is also the
sound source that is most affected by the open-ear acoustics of a
non-occluding coupling.
A brief review of the ear-level FM-only real-ear verification process
includes the following steps:
RESR (real-ear saturation response) measures are completed
at maximum volume settings using a high intensity pure-tone
swept input
REAR (real-ear amplified response) measures are completed
using calibrated speech or speech-weighted inputs in order to
adjust the use volume of the FM-only receiver
RESR measures should be repeated at recommended use volume
settings
Direct sound inputs are evaluated with the ear-level FM system
in place to estimate audibility of the unamplified sound-path
portions of the teacher’s voice and the audibility of other talkers
at different distances from the student

Leisha R. Eiten
81
Figure 3. Verification Option 1. Curve 1 (horizontal hatches) represents audibility
of the unamplified pathway. Curve 2 (vertical hatches) represents audibility of the
amplified pathway.
Figure 4. Test equipment set-up for verification Option 2.
Real-Ear Test Options
Real-ear electroacoustic verification can be performed using a
number of currently available hearing aid test systems. All test
systems should have a calibrated real-speech or speech-weighted
input signal available, as well as a high level pure-tone swept
signal. The specific verification steps that are used will vary depending
on the real-ear test system. Most current test systems fall into
one of two types. The first type, defined as Option 1 in Supplement
A of the AAA HAT Guidelines (AAA, 2008) has an FM instrument
option that provides FM-specific amplification targets and allows
the FM microphone/transmitter to be placed inside the sound
chamber with the real-ear probe measuring the response of the
amplified sound path in the person’s ear, as seen in Figure 1. With
this type of test system, the reference microphone is active in the
sound chamber, not in the sound field. Real-ear verification of the
amplified sound pathway consists of evaluation of the maximum
output and use-volume settings of the FM-only device. First, the
FM receiver volume is set to full-on volume and an 85 dB SPL puretone
swept input is presented to the FM microphone inside the
test box. Sound pressure level measurements are made in the ear
of the child wearing the FM-only receiver. The maximum output
level of the FM receiver may require re-programming or adjustment,
in which case maximum output is then re-measured. Next,
the recommended use-volume setting is confirmed. Calibrated
speech or speech-weighted signals at chest-level inputs of 85 dB
SPL or boom-level inputs of 95 dB SPL are presented to the FM
microphone in the test box and the volume of the FM receiver is
adjusted to match amplified audibility targets. These first 2 veri -
fication steps are illustrated in Figure 2. Maximum real-ear output
should be confirmed at the recommended use volume. Verification
of the unamplified sound path should be completed with the earlevel
FM system in place, but without inputs to the FM microphone/transmitter.
Open-ear instrument targets and a variety of
input levels can be used to estimate audibility of different sound
sources in the environment. This step is illustrated in Figure 3.
The second type of test system, defined as Option 2 in Supplement
A of the AAA HAT Guidelines, does not typically have prescriptive
targets for FM instruments. With this type of test system

82 Assessing Open-Ear Edulink Fittings
Figure 5. Verification Option 2. Ear canal resonance of
unoccluded ear.
Figure 6. Verification Option 2. Maximum output measurement
at volume full-on.
the FM microphone is placed outside the
test box at the calibrated position in the
sound field. The real-ear microphone is
placed in the child’s ear, as illustrated in
Figure 4. After calibrating the sound-field
loudspeaker with the child in the calibrated
position in front of the loudspeaker, the
reference microphone is de-activated. An
unoccluded ear-canal resonance measure
is recorded using a 75 dB SPL speechweighted
input signal. An ear-canal resonance
response is seen in Figure 5. The
child is then moved away from the calibrated
position and the FM microphone/
transmitter is substituted in the child’s
previous position. In this condition, it may
be difficult to place both the FM microphone
and child at appropriate distances
from each other and from the sound field
loudspeaker.
As with test Option 1, real-ear verification
of the amplified (FM) sound pathway con -
sists of evaluation of the maximum output
and recommended use-volume settings of
the FM-only device. First, the FM receiver
is set to full-on volume and a 90 dB SPL
pure-tone swept input is presented to the
FM microphone placed at the calibrated
position in front of the sound-field loudspeaker.
Sound pressure level measurements
are made in the ear of the child wearing
the FM-only receiver. Care should be taken
to ensure that the FM-only receiver is
not close to the sound-field loudspeaker
during evaluation of the FM response, as
high input levels to the FM microphone
could enter the child’s ear as part of the
direct pathway and affect the response
measured in the child’s ear during FM verification.
Because prescriptive targets for
FM systems are not typically provided in
Option 2, published prescriptive output
levels may be used for reference when per -
forming real-ear maximum output measures.
A general clinical approach that can
be employed is to not exceed a peak RESR
(real-ear saturation response) level of 105
dB SPL when fitting an FM system on a
normal-hearing ear. As previously stated,
the maximum output level of the FM
receiver may require re-programming or
adjustment, in which case maximum output
is then re-measured. Maximum output
measures using this verification option are
shown in Figure 6. The goal when evaluating
use-volume settings with this type of
test system is unity gain; that is, little or no
additional gain or attenuation is applied
to the FM response when compared to the
previously measured open ear canal response
with a 75 dB SPL speech-weighted
input. Using input levels of 80 dB SPL
to represent chest-level inputs or 90 dB
SPL to represent cheek- or boom-level
inputs to the FM microphone/transmitter,
the FM receiver volume is adjusted to
match the peaks of the FM response in
the 1000-4000 Hz range to the previously
measured open-ear response. A unity gain
response curve is seen in Figure 7. Once
again, real-ear assessment of the direct,
unamplified sound path is completed with
the ear-level FM system in place, but without
inputs to the FM microphone/transmitter.
With Option 2, all direct sound
path measurements must be made with
the child placed in the original calibrated

Leisha R. Eiten
83
Figure 7. Verification Option 2. Unity gain response of FM at use-volume.
position in front of the sound-field loudspeaker. A variety of
input levels can be used to estimate inputs from different sources
(Pearsons, Bennett, & Fidel, 1977).
Figure 8. Behavioral verification using MLV speech presentation.
Behavioral Verification
Real-ear verification confirms that an ear-level FM-only system
functions as expected on a student and establishes the recommended
use-volume settings. Behavioral verification provides information
about how much the system benefits the student in a noisy
environment. Behavioral verification is an adjunct to but not a
substitution for real-ear verification of the FM-only receiver’s realear
gain and output. When performing behavioral verification,
priority should be given to testing in noise. Performance on speech
perception tasks with and without the FM system can be compared
to determine if the FM-only HAT will be of benefit to the child in
the classroom environment.
The behavioral verification process includes the following steps:
Evaluate speech perception performance in noise without
the FM system
Evaluate speech perception performance in noise with the
FM system in place
In order to closely control the speech and noise presentation
levels and enable highly repeatable testing, behavioral verification
is most often completed in a calibrated sound-booth. Even in a
clinical test setting, behavioral verification measures using speech
stimuli should be completed under conditions that are as representative
as possible of typical classroom listening environments
for the individual child. The vocabulary level and language competence
of the child must also be considered.
A variety of presentation levels could be used when completing
behavioral verification. The AAA remote-microphone guidelines
recommend a beginning speech presentation level of 50 dB HL
from the test-room loudspeaker (65 dB SPL) to represent the
teacher’s voice at a listening distance of 2 meters. This level is
used to represent unamplified inputs to the child without the FM
active. Other levels are: 55 dB HL (70 dB SPL) to represent the
teacher’s voice at a listening distance of 1 meter and 40 dB HL
(55 dB SPL) to represent conversational levels of speech from
2 meters (Pearsons, et al, 1977).

84 Assessing Open-Ear Edulink Fittings
Because the priority of behavioral verification is for testing in
noise, the noise level in the test environment should also be carefully
chosen. In order to best represent the child’s own classroom
environment, noise measurements in the classroom should be
completed when feasible. As a general starting point, Supplement
A of the AAA Guidelines recommends a 0 dB signal-to-noise ratio
to compare performance without and with the FM system active.
Average classroom noise levels measured in occupied classrooms
range from 48-70 dBA (Pearsons, et al, 1977; Jamieson, et al,
2004). Choosing a 50 dB HL noise level assumes a noisier-thanaverage
classroom environment. If the child is not able to perform
speech testing at a 0 dB signal-to-noise ratio without the FM
active or classroom noise measures indicate a lower occupied
noise level, a lower noise level should be selected for behavioral
verification.
The AAA Guidelines detail behavioral testing steps for 2 primary
testing configurations. The first configuration illustrates testing
using monitored-live-voice (MLV) presentation of the speech signal
with the test examiner wearing the FM microphone/transmitter.
Unamplified speech and noise are presented together from one
loudspeaker at 0 degrees to the listener. Figure 8 illustrates the
basic test-booth configuration for MLV behavioral verification.
The second configuration illustrates behavioral verification using
2 or more loudspeakers with the FM microphone placed 3-6 inches
from the primary loudspeaker presenting a recorded speech signal
which may be placed at either 0 or 45 degrees, and noise presented
from the secondary loudspeaker(s) at 45, 180 and/or 315 degrees.
Figure 9 illustrates the test set-up for Configuration 2, which
is behavioral verification with the FM transmitter off. Testing is
then repeated with the FM transmitter turned on, using the same
test configuration.
Test configuration 1 (MLV presentation) is the only behavioral
verification option if only one soundfield loudspeaker is available
in a clinical test booth. Because speech and noise are presented
together from a single loudspeaker, the FM signal must be transmitted
directly from the tester wearing the FM microphone
outside of the test room. This requires monitored-live-voice
Figure 9. Behavioral verification using recorded speech testing.
presentation of the speech signal to both the loudspeaker and the
FM microphone.
Test Configuration 2 (recorded speech presentation) requires
more than 1 loudspeaker, because no improvement in performance
would be expected if the FM microphone was placed in front of
a single loudspeaker with speech and noise presented together at
a 0 signal-to-noise ratio. In this case, the FM microphone would
receive and transmit both the speech and the noise together and
no improvement would be expected with the FM microphone
active. Other factors to consider with behavioral test configuration
2 are that the characteristics of the loudspeakers in the nearfield
should be known and the input levels at the 3-6” distance
and the calibrated position be evaluated in advance using a soundlevel
meter. This is to ensure that the appropriate input level is
present at both the FM microphone position and the listener’s
position. Test configuration 2 provides more consistency and
repeatability for the speech test itself, but requires more measurement
and control of the booth and speaker variables before
testing takes place.
Performance on speech tasks with the FM system active should
significantly improve relative to performance without the FM.
However, verification in a clinical test booth is still only an estimate
of real-world classroom performance. Therefore, validation
and monitoring is recommended for confirmation of ear-level
FM-only benefit in the child’s learning environment over time.

Leisha R. Eiten
85
When considering behavioral verification options, one caution is
needed regarding adaptive speech-in-noise tests. Although some
published research protocols with FM systems (Boothroyd, 2004;
Lewis, Crandell, Valente and Horn, 2004; Schafer and Thibodeau,
2006) have used adaptive speech-in-noise tests such as the HINT
or HINT-C (Nilsson, Soli and Sullivan, 1994; Nilsson, Soli and
Gelnett, 1996), as well as variable speech or noise levels such as
the QuickSIN or BKB-SIN (Killion, Niquette, Gudmundsen, Revit
and Banerjee, 2004; Etymotic Research, 2005), adaptive tests
are not generally recommended for behavioral verification of
FM systems. The adaptive test paradigms require that either the
noise or speech input levels be varied to achieve 50 % correct
performance. If the speech adapts, the intensity level could be
lower than the typical input level and be altered differentially by
the compression features of the transmitter throughout the test.
If the noise adapts, the level should not exceed that which would
be encountered in typical classroom use. Adaptive or variable
speech-in-noise tests continue to be appropriate for determining
HAT candidacy.
Conclusion
With the increasing complexity of FM systems as well as hearing
aid test options, standardized verification of ear-level FM-only
devices such as the Phonak Edulink TM is important to assure appropriate
function and benefit for each student. Non-occluding
fittings are commonly used with these devices and present unique
verification challenges for the audiologist. Combining real-ear
test techniques and behavioral measures provides a comprehensive
picture of expected audibility and benefit from ear-level FM-only
devices.
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American Academy of Audiology (April, 2008). AAA Clinical Practice Guidelines:
Remote microphone hearing assistance technologies for children and youth
birth-21 years.
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Children. Seminars in Hearing, 20(2).
Etymotic Research (2005). BKB-SIN Test, Version 1.03 (Compact Disk).
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