Frequency Transposition in hearing aids for school-age

children

Jenny Smith1,2,Marilyn Dann1 and Margaret Brown1 1 Deafness Studies Program, Graduate School of Education, University of Melbourne, Australia.

2 Jenny Smith, Audiological Consultancy, South Yarra, Australia

Contact: jensmi@ozemail.com.au

Basic Principles

All children need to access the high frequency fricatives, such as /s/, /t/ which are critical in spoken English

Children with severe /profound high frequency loss have greater difficulties accessing these speech cues.

“Dead regions” (> 75dB) do not hear, regardless of gain

Frequency transposition is an alternative way of accessing high frequency cues and has relevance for children due to their greater neural plasticity.

What are the problems ?

In the past, frequency transposition has not been very successful due to :

Technical limitations of the signal processing which produce processing artefacts

Very different types of transposition frequency maps Different fitting strategies regarding the degree of transposition Different target audiograms, ski-slope , corner, or U-shaped Time allowed to make use of altered cues The amount of training provided to the user

( Dillon, 2007, pers.comm)

Can new DSP aids help overcome the limitations ?

The project

Evaluate linear frequency transposition Verify the degree of transposition using REM

Evaluate with ski-slope losses

Evaluate in schools with facilities for training Measure over time to allow for adaptation

But first, find the subjects ! I approached 11 schools to find 6 children

History

Key goals: To optimize the use of good low frequency hearing To provide high frequency access by frequency transposition, AE To improve cosmetic appeal and hearing aid usage

Boy, aged 14.4 years Hearing loss caused by lack of oxygen at birth Hearing aids fitted under 12 mths Always a reluctant aid user Attending mainstream school, with minimal educational support

Widex Inteo IN9-AE elan flex aids IN9 fitted using basic protocol

Sensogram and feedback test 3 weeks acclimatisation Positive response

Introducing Frequency transposition Audibility Extender (AE) set as first program, P1 P2 (master) and VC options provided Start freq = 2000Hz, Expanded, Gain= +10dB

Reviewing Frequency transposition rejected by subject as too confusing, echoic, slushy Counsel about options, review again, check data log Evaluated using live speech mapping

Setting AE

Turquoise AE=2000 E Purple AE= 2000 BGreen AE=2500 B Blue AE=3200 B

Verifying the Fitting

VC = maximum

Evaluating Aid Benefit

Parameter Test Speech Perception CNC words and phonemes

Speech Articulation Goldman-Fristoe Test of Articulation

Speech Production Recorded speech sampling

Changes in classroom listening

Teacher /student LIFE

Changes in overall hearing Parent/student Questions and interviews

Speech Perception Testing Presentation

Tested with Consonant-Nucleus-Consonant (CNC) monosyllabic word lists Live voice presentation at normal speech levels at 1 m. in a quiet room Tested pre-fitting, at fitting and post -fitting every 6 weeks for 24 weeks.

Protocol Two lists presented with AE-ON and two lists with AE-OFF One list given audio-visually and one audition alone, for each setting Responses for words and phonemes scored live and recorded on video

Responses Scored by two experienced transcribers with normal hearing Scored by a third experienced transcriber if these scores varied by >8%. Mean of the two closest scores used for further data analysis.

Speech Perception : CNC words

Mean word scores, audition alone

30

35

40

45

50

55

60

65

fit 6 w eeks 12 w eeks 18 w eeks 24 w eeks

time

% c

orr

ect

AE-ON AE-OFF

Significantly better scores recorded 6 weeks post-fit and sustained over time

Mean phoneme scores, audition alone

60

65

70

75

80

85

90

fit 6 w eeks 12 w eeks 18 w eeks 24 w eeks

time

% c

orr

ect

AE-ON AE- OFF

Speech Production: G-F 2 Test

Pre-Fit 54

Post-Fit 90

Spoken English Spectrographic Analysis: Plant, 2007

Classroom listening: LIFE

Pre-Fit % IN9 –M %

3wks post-fit

IN9-AE %

12 wks post -fit

63.3 86.6 81.6 (+ 18.3%)

+35 +17 0 -17 -35

LIFE Student Response

LIFE Teachers Response

+35 = Strong support for positive change: use is highly beneficial 12 weeks post FT introduction

Described benefit

Student Parent

Hearing new sounds I hear the phone ring and the kettle boil

Definitely hearing car indicators and gears

Hearing high soft environmental sounds

I heard the birds Not that I have observed

Responding better in 1:1 conversations

I hear the whole sentence Most definitely

Participating more in family discussions

One at a time is OK Not really, he’s a teenager

Understanding unknown speakers

Same as old aids Sometimes

Changes in own speech Sounds different Much clearer, even his grandfather commented

Overall comment I am hearing,

not deaf

These aids are working wonders for him

Hearing Aid Outcomes

Child 1: Extreme ski-slope hearing loss

Increased willingness to wear hearing aids Significant sustained improvements in speech

perception and speech production Improved listening skills in the classroom and at home Significant changes in confidence, self esteem and

self-image

“These aids are working wonders for him”

History

9.6 year old girl

Serious medical condition needing extended hospitalization with hearing loss reported to be due to ototoxic drugs (gentamyacin)

Fluctuating conductive overlay

Attends mainstream school with oral and signing support but struggles to access the curriculum

Figure 1:Unaided audiogram

WIDEX Inteo IN19 + Audibility Extender (AE)

IN19 fitted using basic protocol Sensogram and Feedback test 3 weeks acclimatisation

Introduce Frequency transposition Audibility Extender (AE) set as first program, P1 Master program and volume control deactivated Start frequency = 2500Hz, Expanded, Gain= +10dB Identification LING 7 sounds confirmed access to /s/, /sh/

On review: no adjustments indicated

Verifying the Fitting

Speech Perception : CNC words

Significantly better scores with frequency transposition (AE-ON) over timeMiddle ear infection and school holidays linked to poorer scores at 12-18wks

mean phoneme scores, audiovisual

70

75

80

85

90

95

100

fit 6 weeks 12 weeks 18 weeks 24 weeks

time

% c

orre

cr

AE-ON AE-OFF

mean phoneme scores, audition alone

45

50

55

60

65

70

75

80

fit 6 weeks 12 weeks 18 weeks 24 weeks

time %

cor

rect

AE-ON AE-OFF

Speech Production

16 new words

Pre-fit 64.8%

18 wks Post-fit

79.6%

Benefit 14.8%

SWAT Test 108 Single Words (Paatsch,1997)

G-F 2 Test

Pre-Fit 78

24 wks Post- Fit

78

Improved productionconsonant clusters/fr/ /kr/ /kw/

Spoken English

Pre-FitPost- Fit

Data Logging Interpretation

Hearing Aid Outcomes

Child 2: Severe hearing loss

Improvements in speech perception Measured changes in speech production of isolated

words Perceived improvement in listening and auditory

awareness

“She is more aware, more on task, more tuned in”

15.5 year old girl Congenital hearing loss Good oral communicator Age at first fitting: 19mths Left cochlear implant: 4.8yrs

Always worn bimodal aid

Considering bilateral cochlear implants

Frequency transposition aid trialed as an alternative

Unaided right hearing levels, No measurable left hearing

History

WIDEX Inteo IN19 + Audibility Extender (AE)

IN19 fitted using basic protocol Sensogram and Feedback test Immediate introduction of AE

Frequency transposition settings Audibility Extender (AE) set as first program, P1 Master program and volume control active Start frequency = 2500Hz, Expanded, Gain= +14dB

On review: rapid acclimatisation, no adjustments needed She did not use either P1 or volume control

Verifying the Fitting

Speech Perception

Aid scores show the added benefit provided to the CI

Audition alone scores show the importance of visual cues

CNC Word %

CNC Phoneme%

BKB Sentence%

IN19-AE

Audio-visual34 68 46

Triano SP Audio-visual

28 62 40

CI+IN19-AE

Audio-visual86 93.3 86

CI+IN19-AE Audition only

6 19.3

Results show a synergy for CI + aid + lip-reading.

Mother Her initial comment was “I can not only hear you, but I can understand what

you’re saying” which was amazing.

My daughter says “ both the ears are now listening at approximately the same level, rather than having the cochlear implant listening level high and the hearing aid level low. Both the ears are getting a similar input ”

“I was behind her and she was reading a book with only the new hearing aid on ( no CI) and we had a short conversation. It was amazing she could have a proper conversation without lipreading”

There are lots of differences in her sentence structure – she is starting to use final consonants better and her past tense has improved, she is putting on /t/ and /d/ , and she now says “women” not “womans”

The teachers at school asked if she had got a new hearing aid over the holidays as her speech was a lot clearer and she was listening better.

I didn’t think the improvement would be as good as it was. It is not so urgent to get a (second) cochlear implant now.

Hearing Aid Outcomes

Child 3: Bimodal fitting for a profound loss

A synergy can be observed between the cochlear implant, the frequency transposition aid and lipreading

Improved hearing in complex situations with both the family and at school

Perceived improvements in spoken English with better final consonants

“Listening is a nice round package for her now””

Educational Outcomes

“Learning to Listen”

A boy who refused to wear hearing aids – his mother said “ he sabotages his hearing aids”

A boy with no additional oral support at school A boy who found it difficult to adjust to AE

New Listening Behaviours

He is now trying hard to learn to listen

There are rewards – what he hears is meaningful

He trusts what he hears He is trying to work out the

vocabulary to describe his auditory perceptions

Acknowledgements

This project would not have been possible without the support and co-operation of the children, their families and their teachers. I thank them all most sincerely.

I am grateful to Widex Denmark for the provision of hearing aids, to the late Geoff Dixon and Widex Australia for technical support and ear moulds and to Sonic Innovations, Australia for supply of REM equipment.

Dr Janet Doyle provided invaluable help in data analysis and a critical review of the manuscripts.

Widex Denmark supported the production of both poster and papers.

All information documented here is original work and has not been funded by any outside agency.