Fitting and Evaluation of FM Systems for Cochlear Implant Users Linda M. Thibodeau.

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

www.cochlearamericas.com


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


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


www.frye.com


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


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



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)


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


FM Transmitter: Phonak Campus S

FM Receivers-Set to Double Dots to get FM + M Adaptor set to FM+M


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


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


Measurement Steps

Part I: Input to CI mic

Part II: Input to FM mic

Part III: Compare Outputs


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 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


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


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…..

Fitting and Evaluation of FM Systems for Cochlear Implant Users Linda M. Thibodeau.

Documents

fm receiver slide

fm microphones

fm transmitter

ci fm interface

electrical coupling

evaluation of fm systems

electroacoustic testing

child informal testing