The use of FM systems with Cochlear Implants- How has research had an

impact on practice?

Sarah Flynn and Elizabeth Wood

South of England Cochlear Implant Centre

University of Southampton

Co - workers

• Julie Eyles

• Catherine Sammons

• Mark Lutman

• Paula Greenham

• Margie Harriott

Why use assistive listening devices?

• Listening conditions outside the clinic• Proven benefit of FM radio aids with

hearing aids in classroom situations• Direct rehabilitation at hearing deficit

rather than overcoming poor listening environment

Signal to noise ratio

Reduce speaker to ear distance

Desired sound predominates over background noise

Sound treat classroom

Reduce overall level of background noise

Research rationale

• Older children and adults for sound quality rating

• Word discrimination testing in pink noise simulates classroom conditions

• Testing at distances up to 10 metres to simulate teacher’s distance from child

• Standard conditions to compare different processor and radio aid combinations

• No change to processor sensitivity setting

McCormick Automated Toy Test (ATT)

• Word discrimination task for young children

• Adaptive technique allows comparison without doing many word lists

• 71% words correct in dB (A)

Results of earlier studies

In noise• All subjects benefited

from using an FM system

• Mean FM improvement in quiet = 7dB

• Mean FM improvement in noise = 15dB

Over distance• Sound quality reported

as good at 1m, 3m and 10m

• Mean FM improvement at 1m and 3m = 14dB

• Mean FM improvement at >10m = 10dB

Phonak Microlink MLXs

Initial results with ESPrit 3G

• 4/11 subjects reported problems with the clarity of the FM signal with MicroLink MLx

• Large variability between subjects • Identified a need for change in programming

parameters of processors - monitor earphone setting should not be enabled for the map suitable for FM / accessories

Follow-up study of FM radio aids with ESPrit 3G

• 3 radio aids MicroLink MLx, Genie and Solaris• 10 subjects• Each subject used the MLx and one other system• 2m in noise with and without FM• Distance –

• 3m in quiet no FM• 3m and 10m in quiet with FM

Results of FM radio aids with 3G

In noise• All 3 FM systems

performed well • Solaris 7.3dB

improvement• Genie 11.0dB

improvement• Microlink 8.3dB

improvement

Over distance• Sound quality was >83%

for all 3 systems • 3/10 preferred the

Microlink MLx for its ease of wearing

• 5/7 preferred the Genie due to louder sound

• ATT results were better with the Genie, than MLx

Further research questions

• Does the microphone option for the handy mic of the MLx system influence the results?

• Would the MLx be more acceptable to users if there was a higher gain option?

Microphone options

Handy mic with MLx Better performance

with the omni microphone setting in noise

Omni gave slightly better results than zoom and much better results than superzoom over distance

Campus S with MLxS

Slightly better performance with the omni microphone setting in noise and over distance

Campus S and MLxS with the 3G

• MLxS receivers with gains of 10, 16 and 20 gave a significant improvement in noise

• At 10 metres, a gain of 16 was significantly better than 10, but 20 was not better than 16

• 4/7 subjects said the 10 gain MLxS was too quiet although sound quality was rated as good

• 3/7 subjects said the 20db gain MLxS was too loud to listen to for a long time

Research conclusions

• All the FM radio aids tested can be used with cochlear implants

• MicroLink MLx – less gain for 9/10 subjects at 3m and 10m

• Microlink MLxS – – Gain of between10 and16dB appropriate for most

users but one level is unlikely to suit all users– Probable saturation at >16

• Need for patient feedback• Need for good communication between clinic

and education professionals

Radio Aids fitted at SOECIC January 2004

Genie27%

CRM22021%

No FM45%

Sennheiser1%

Solaris5%

Microlink1%

Soundfield FM

Either fixed in room or used as a desktop system

Teacher wears transmitter

Creates a uniform level of sound through the room

Can give approximately a 10 dB advantage

Soundfield FM Conclusions

• Soundfield does give benefit to children and teachers

• Users preferred the personal FM over personal FM and fixed soundfield

• Need to improve room acoustics before using fixed soundfield FM

• Ensure that the soundfield is optimally functioning

Fitting guidance

• Implant user able to indicate sound quality• Willingness to use radio aid with implant• Stable map• Use map with monitor earphones not enabled• Correct FM lead• Recommended transmission frequency• Wearing position• Communication with local professionals

Fitting the FM system

• Listening check of FM radio aid

• Set output of radio aid to be compatible with that from the cochlear implant on its own

• Validation of settings (McCormick ATT)

• FM booklet

Interference• Any unwanted non-signal noise• Can be caused by

– Interaction between cochlear implant RF signal and radio aid RF signal

– Monitor earphones enabled – Processor and radio aid worn too close together– Distance from transmitter– Receiver searching for signal when transmitter

turned off– Furniture eg metal objects– Smoke alarms, taxis, mobile phone masts

Simple checks

• Having monitor earphones to check processor on its own (use monitor earphones enabled map on 3G)

• With Sprint listen through monitor earphones to radio aid system and processor together

• Check radio aid system with processor on 0 sensitivity

• Check accessory adaptor is used with ESPrit 3G processor

• All connections fully engaged• Microphone of Campus S switched on

Helpful Hints for long term radio aid use

• Good communication between implant centre and local services

• Patient card with programme locations• Seating position in room• Processor + FM signal must be consistent

over time

References1 Benefit of FM study : Speech Discrimination in

Noise (January 2000)2 Speech Discrimination Ability and Sound

Quality with FM over distance (April 2000)3 FM survey (June 1999/ May 2000)4 Soundfield Systems used with Personal FM

and CI (2002)5 Benefit of FM with 3G - distance/noise (2003)6 Benefit of FM with 3G - 3 FM systems (2003)