fitting and evaluation of fm systems for cochlear implant users
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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 CouplingDesktop Soundfield FM systems
Electrical CouplingPatch cords connect FM Receiver to CIDirect Plug-in of FM Receiver
T-Coil CouplingProcessor has t-coil to receive electromagnetic
signal from the Body-worn FM system with Neckloop
Electrical Coupling- FM and CI
BODY-LEVEL
PROCESSORSCOCHLEAR
IMPLANTS EAR-LEVELPROCESSORS
BODY-LEVELFM RECEIVERS RECEIVERS
EAR-LEVELRECEIVERS
Body-worn Speech Processor
Ear-level Speech Processor
Body-Worn
FM Receiver
Miniature Cord-
Connect FM
Receivers
MiniatureDirect-
ConnectFM
Receiver
T-Coil Coupling- FM and CI
Requires Speech Processor with T-Coil such asNucleus 3G
Verification Procedures for the CI+FM Interface1) Informal Testing
2) Behavioral Testing
3) Electroacoustic Testing
Verification Procedures for the CI+FM Interface
1) Informal Testing
Informal Testing
Can be performed by the classroom teacherQuick and easy way to determine that CI and FM are functioning3 Types:
1. Using a speaker2. Using monitor earphones3. Performing a listening Check –
subjective response required from child
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. 277-1008C)Speak into the transmitter microphoneListen 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
Available for Nucleus Processors:
1. ESPrit 3G BTE
2. SPrint Body-Worn
Informal Testing
--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
ESPrit 3G with Monitor Earphones
SPrint with Monitor Earphones
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 earphonesTurn on Speech Processor, FM transmitter, FM receiverSpeak 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
Informal Testing
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Verification Procedures for the CI+FM Interface
2) 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
Behavioral Testing
Acronyms
Cochlear Implant Alone
BCI55BCI55/50
Cochlear Implant + FM System
BFMCI55/50BFMCI55
Measure Speech Recognition with CI alone
BCI55Measure 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/CI55/50Case studies for Two Children Using
Nucleus 3G Processors and Phonak MLxS Receivers
Subject CI/FM CI: Quiet
CI: Noise
CI+FM: Noise
Case #1 3G/MLxS 92% 72% 88%
Case #2 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 45.50 % (CI alone)BCIFM55/50 75.25 % (CI + FM)
The average improvement when adding the FM system in noise was
29.75%
BCI55 76.00% BCIFM55 75.24%
The difference between CI alone and CI+FM in Quiet was minimal.
Behavioral Testing
Verification Procedures for the CI+FM Interface
3) Electroacoustic Testing
Electroacoustic Testing
ELECTROACOUSTIC PROCEDURESto 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 SystemsVerify output for input to
-CI microphone, and
-FM transmitter microphone
Determine FM advantage
Electroacoustic Testing
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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 ORAdaptor cord from Speech
Processor to analyzer
Electroacoustic Testing
Equipment for Electroacoustic Testing
ESPrit 3G – One Control either programmed for Sensitivity or for VolumeUnits 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 1-
20)
Electroacoustic Testing
Processor Knob Control
Volume
Modifies the intensity to the listener of that which has already
been detected
SensitivityThe quietest sounds that
the speech processor will detect from the
microphone and convert into stimulation
Adapted from Nucleus 24 Technical Bulletin December 1998-Febuary 1999 / Issue No. 6
G
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
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
Connections for Testing Procedure
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
Electroacoustic Testing
Part II: Measuring RMS for Input to the FM Transmitter1. 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
Volume programmed to default (100% of Electrical Dynamic Range, equivalent to 9 on SPRINT)
FM Advantage = RMS Difference between EFM/CI80 and ECI/FM65
MLxS programmedto +10 and +24 Advantage via
Toasting
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 ANDVERIFY FM FITTINGS
WITH COCHLEAR IMPLANTS
SO THAT…..