Fitting and Evaluation of
FM Systems for
Cochlear Implant Users
Linda M. Thibodeau
Cochlear Implants and FM Systems
THREE BASIC WAYS TO USE
FM SYSTEMS WITH CIs
Audio Coupling
Desktop Soundfield FM systems
Electrical Coupling
Patch cords connect FM Receiver to CI
Direct Plug-in of FM Receiver
T-Coil Coupling
Processor has t-coil to receive electromagnetic
signal from the Body-worn FM system with
Neckloop
Electrical Coupling- FM and CI
BODY-LEVEL
PROCESSORS
COCHLEAR
IMPLANTS
FM RECEIVERS
EAR-LEVEL
PROCESSORS
BODY-LEVEL
RECEIVERS
EAR-LEVEL
RECEIVERS
Body-worn Speech
Processor
BodyWorn
FM
Receiver
Miniature
DirectConnect
FM
Receiver
Miniature
CordConnect
FM
Receivers
Ear-level Speech
Processor
T-Coil Coupling- FM and CI
Requires Speech Processor with
T-Coil such as
Nucleus 3G
Verification Procedures
for the CI+FM Interface
1) Informal Testing
2) Behavioral Testing
3) Electroacoustic Testing
Verification Procedures
for the CI+FM Interface
1) Informal Testing
Informal Testing
Informal Testing
Can be performed by the classroom
teacher
Quick and easy way to determine that CI
and FM are functioning
3 Types:
1. Using a speaker
2. Using monitor earphones
3. Performing a listening Check –
subjective response required from
Informal Testing
Speaker for Cord-Connect and
Direct Connect Receivers
Plug the FM receiver
into an amplifier
speaker:
Radio Shack Mini
Amplifier Speaker
(Cat. No. 2771008C)
Speak into the
transmitter
microphone
Listen to the output
through the amplifier
speaker
Informal Testing
Monitor Earphones
Can hear output from CI mic.
before it is processed and sent
to the electrode array
Can hear output for input to CI
and FM simultaneously
ESPrit 3G
with Monitor
Earphones
Available for Nucleus
Processors:
1. ESPrit 3G BTE
2. SPrint Body-Worn
--Can listen to output from input to CI microphone for ESPrit 22
and 24 BTE’s, but cannot listen to or plug in the FM at the same time
SPrint
with Monitor
Earphones
Informal Testing
Monitor Earphones
Other BTE speech
processors that have
monitor earphones
ESPrit 22
ESPrit 24
Can listen to output when
there is input to CI
microphone via the
earphone, but
cannot plug in the FM
Receiver at the SAME
time!
Informal Testing
Procedure for Using
Monitor Earphones
Connect FM and
monitor earphones
Turn on Speech
Processor, FM
transmitter, FM
receiver
Speak into both CI
and FM microphones
separately
Informal Testing
Listening Check
KEY TO LISTENING CHECKS:
Must give input to both microphones
separately
Have the child repeat or act out what you
say:
1. Ling – ah, oo, ee, sh, ss, mm
2. Numbers – one, two, three
3. Count syllables – ba, ba, ba
4. Long or short – baaaaa, ba ba ba
5. Simple commands – Hide your face
6. Speech awareness with play – rings, blocks, etc
www.cochlearamericas.com
Verification Procedures
for the CI+FM Interface
2) Behavioral Testing
Behavioral Testing
Behavioral Testing in the Booth
A modified ASHA
procedure is used for
behavioral
testing with FM systems
Speech recognition is
the most effective way to
measure behavioral
benefit with an FM
system
Behavioral Testing
Testing Equipment for Speech
Recognition
Soundbooth with
soundfield
speaker and seating
at a
zero degrees azimuth
Audiometer that
allows
for live voice speech
recognition (SR)
testing
Appropriate SR
material with multiple
lists
Behavioral Testing
Setup for Testing a Child with a CI
Seat the child at 0
degrees azimuth
Check CI functioning with
monitor earphones or
informal listening check
Select presentation level
for stimuli that is
appropriate
for the child’s hearing
thresholds -Ideally 35
dBSL
Acronyms
Cochlear Implant
Alone
BCI55
BCI55/50
Cochlear Implant
+ FM System
BFMCI55/50
BFMCI55
Behavioral
Testing
Measure
Speech
Recognition with
CI alone
BCI55
Measure SR in
quiet with the CI
alone
BCI55/50
Measure SR in
noise with the CI
alone at a
+5 SNR
Behavioral Testing
Measure Speech Recognition with
CI Interfaced with FM System
Attach the FM
system and verify
functioning
BFM/CI55/50
Measure SR in
noise with the
CI+FM at +5 SNR
BFM/CI55
If time permits,
measure SR in quiet
with the CI+FM
Behavioral Testing
Compare Conditions
Compare percent correct scores with
and without use of the FM System
Two most important conditions for
comparison are:
BCI55/50 and BFM/CI55/50
Case studies for Two Children Using
Nucleus 3G Processors and Phonak
MLxS Receivers
Subject
CI/FM
Case #1
Case #2
3G/MLxS
CI:
Quiet
92%
CI:
Noise
72%
CI+FM:
Noise
88%
3G/MLxS
92%
68%
84%
Stimuli: PBK words; Presentation levels: case #1, 65/60; case #2 55/50
Behavioral Testing
Behavioral Results
Thibodeau, Schafer, Overson, Whalen, Sullivan (2005)
BCI55/50
BCIFM55/50
45.50 % (CI alone)
75.25 % (CI + FM)
The average improvement when adding the FM
system in noise was
29.75%
BCI55
BCIFM55
76.00%
75.24%
The difference between CI alone and CI+FM in
Quiet was minimal.
Electroacoustic Testing
Verification Procedures
for the CI+FM Interface
3) Electroacoustic Testing
ELECTROACOUSTIC PROCEDURES
to Evaluate FM systems with Cochlear Implants
New Monitoring Earphones provide a
convenient way to monitor the output of
the CI microphone relative to that of the
FM microphone prior to being delivered
to the electrode array.
Only Nucleus 3G and Sprint Processors
allow this earphone to be attached AT
THE SAME time as the FM Receiver
Purpose of Electroacoustic
Testing with CIs and FM
Systems
Electroacoustic Testing
Verify output for input to
-CI microphone, and
-FM transmitter
microphone
Determine FM
advantage
www.frye.com
Electroacoustic Testing
Electroacoustic Testing
 Acoustic output from a
CI monitor earphone is
used to verify functioning
and to measure the FM
advantage
 Currently available on
Nucleus ESPrit 3G and
SPrint
 A modified ASHA
procedure is used for
testing the FM systems
electroacoustically
Electroacoustic Testing
Equipment for Electroacoustic
Testing
Speech processor
Monitor earphones
Hearing aid analyzer: Fonix FP40
Coupler: ½ to 1 inch adaptor OR
Adaptor cord from Speech
Processor
to analyzer
Electroacoustic Testing
Equipment for Electroacoustic
Testing
ESPrit 3G – One Control either programmed for
Sensitivity or for Volume
Units today are set:
P1-Sensitivity (Range 1-7)
P2-Volume (Range 1-7)
SPrint
Separate Controls for
Volume – Middle no. on display (Range 1-9)
Sensitivity – Right no. on display (Range 120)
Processor Knob Control
Sensitivity
Volume
The quietest sounds that Modifies the intensity to
the speech processor
the listener of that
will detect from the
which has already
microphone and
been detected
convert into
stimulation
G
Adapted from Nucleus 24 Technical Bulletin December 1998-Febuary 1999 / Issue No. 6
Electroacoustic Testing
Equipment for Electroacoustic
Testing
FM Transmitter: Phonak Campus S
FM Receivers-Set to Double Dots to get FM + M
Adaptor set to FM+M
Electroacoustic Testing
Connections for Testing
Procedure
1. Connect the CI
speech processor
and the FM receiver
2. Plug the monitor
earphones into the
speech processor
3. Connect the ½ to 1
inch adaptor to the
test microphone or
use adaptor cord
Electroacoustic Testing
Connections for Testing
Procedure
4. Fit one earphone into the
coupler or plug into
analyzer
5. Place the coupler and
earphone in a stable
location outside the
analyzer
6. Turn on the processor,
receiver, and transmitter
Electroacoustic Testing
Measurement Steps
Part I: Input to CI mic
Part II: Input to FM mic
Part III: Compare Outputs
Electroacoustic Testing
Part I:
Measuring RMS for Input to CI
1. Position processor in test
box and close lid
2. Present 65 dB SPL
complex signal: ECI/FM65
3. Place transmitter in quiet
location
4. Record RMS for that
Setting
Part II: Measuring RMS for
Input to the FM Transmitter
1. Place transmitter microphone in
test
box and close lid
2. Present 80 dB SPL complex
signal: EFM/CI80
3. Place processor in quiet location
4. Record RMS for that Setting
Part III:
Calculate FM Advantage
FM Advantage = EFM/CI80-ECI/FM65 (RMS
Difference)
Ideal FM advantage is at least 10 dB
If speech processor is set for sensitivity, adjust
sensitivity knob to improve FM advantage if
necessary
FM Advantage as a Function of
Sensitivity Setting on the 3G
MLxS programmed
to +10 and +24
Advantage via
Toasting
Volume programmed to default
(100% of Electrical Dynamic Range, equivalent to 9 on SPRINT)
FM Advantage = RMS Difference between EFM/CI80 and ECI/FM65
SUMMARY
FM Fittings must be verified in one or
more ways
Informal Testing
Behavioral Testing
Electroacoustic Testing
SUMMARY
Informal Testing
Should be part of daily routine when
FM is connected to CI
Students should be reinforced when
they
alert adult that system is not
working
SUMMARY
Behavioral Testing
Recall that if using Percent Correct
scores,
large differences are needed to be
significantly different
Necessary to verify FM advantage
when
electroacoustic testing cannot be
performed
SUMMARY
Electroacoustic Testing
Can be done for those systems that
allow the addition of the monitoring
earphone while the FM is connected
Necessary to verify FM advantage
SUMMARY
Given the risks, costs, and commitment
associated with obtaining a Cochlear
Implant…
It only makes sense that one would do
everything possible to provide the
most optimal signal….
THEREFORE-------------
CONSIDER FM SYSTEMS
FOR EVERY EAR OF EVERY
CHILD AND
VERIFY FM FITTINGS
WITH
COCHLEAR IMPLANTS
SO THAT…..