evidence-based bimodal fitting bas van dijk · final evaluation of fitting flow bimodal benefit...

Evidence-based bimodal fitting

Bas van Dijk

Bimodal fitting

• Often done by separate

people.

• Difficult??

• What is the goal?

• What is needed is clear

guidance for clinicians,

based on objective data

that gives good, stable

outcomes.

Evidence-based fitting

Theresa Ching 2001

First fitting flow proposedDefault setting in HAPrograms matched

NAL-NL2 or Audiogram+

M1:Melbourne study (N=17)Speech understanding and preference

Modified proposal Matched signal processing

M2: Melbourne study (N=10)Preference only

New proposalMost parameters back to default

programs matched

M3:Melbourne study (N=17)Fine Tuning

Erasmus studyFine Tuning

M4: Melbourne study (N=17)Final evaluation of fitting flow

Bimodal benefit

NAL-NL2 better than own

fitting, No evidence we

need adjustments or

complex loudness

balancing procedure.

Smart Hearing Alliance

Melbourne trial (M1-4)

• 17 experienced bimodal recipients (N6 users, different HAs)

• All converted to Enzo2, Enzo29 or Lynx depending on HL

• Average age 69 years (range 52 to 83 years)

• Average period of implant use 5.3 years (range 0.8 to

11.5 years)

M2: Matched parameter proposal

• Adjusted parameters for best match

– Wind noise reduction

– NR strength

– Environmental optimizer

– Directionality

• Preference take-home study in 10 subjects (out of the original

17)

• 1 person preferred the new setting, 1 person no preference, the

rest clearly preferred the original setting.

• 3 people reported loudness inbalance with new setting, zero

with old setting.

• Reports of speech being unclear and HA not loud enough in

some noisy situations.

Theresa Ching 2001







programs matched




Bimodal benefit



need adjustments or

complex loudness



Not preferred

M3+M4: Device Fitting

• Hearing Aid fitted to NAL-NL2 prescription at 50, 65

and 80 dB SPL

• Sound Processor CP900 (N6)

• SCAN with clinical defaults

M3: Method: Comparison of Loudness Balancing

Approaches

Two approaches evaluated

1. Female continuous discourse at 65 dB SPL

2. International Speech Test Signal (ISTS)

Presented at multiple levels of 55, 65 and 75 dB SPL

Filtered into low-frequency (< 500 Hz), mid-frequency (≥ 500 Hz and ≤ 1000 Hz) and high-frequency (> 1000 Hz)

components

Hearing aid gain adjustments were applied until subject judged the sound from hearing aid and cochlear implant sound processor was centred in the head when listening to both together.

M3-Method: Comparison of Loudness Balancing

Approaches

Preferred gain measures:

Female Continuous Discourse at 65 dB SPL

• Gain adjustments applied based on 65 dB SPL signal

only

International Speech Test Signal (ISTS)

• Gain was adjusted in response to subject reports for

each frequency band and level

• Where there were no thresholds ≤ 90 dB HL for a

particular frequency band, that frequency range was

not used for the balancing.

For each approach, the resulting REIG was measured.

M3-Method: Comparison of Loudness Balancing

Approaches

Bimodal performance measures:

• Speech perception, SRT at 65 dB SPL with adaptive

4TB, S0N0

• Localisation, 13 speaker array in 180 degree

configuration in the horizontal plane, stimuli Pink

noise bursts. The maximum presentation level was

68 dB SPL and level was randomly jittered by up to

8dB in steps of 1 dB

M3-Results: Comparison of Loudness Balancing

Approaches

Average preferred gain preferences at 65 dB SPL (n=17)

Continuous discourse – 15/17 within ±5dB NAL-NL2

ISTS Multi Level – 14/17 within ± 5 dB NAL-NL2

Continuous

Discourse ISTS Multi

Level

M3-Results: Comparison of Loudness Balancing

Approaches

Preferred 3FA gain

Significant correlation between 65

Discourse and 65 ISTS Multi

conditions

NO correlation between corrections

(suggesting that on average one

could just fit to NAL-NL2 without

loudness balancing).

M3:Results: Comparison of Loudness Balancing

Approaches

Bimodal performance

SRT – no significant difference between approaches (n=14)

Localisation - no significant difference between approaches (n=15)

Better

Performance

Theresa Ching 2001







programs matched




Bimodal benefit



need adjustments or

complex loudness


Simple LB as good as complex.

Maybe not needed at all?


Not preferred

SHA- Bimodal Fitting Workflow

NAL-NL2 prescription

• Shown to provide suitable frequency response and gain characteristics for bimodal listeners (English et al, 2016)

Hearing Aid Program Configuration

• Best match to CP900 defaults of SCAN & Custom

• P1 Soft Switching (directionality adjusted based on listening environment)

• P2 Omni-Directional

Simple Loudness Balancing

• Listening with two ears

• Adjust gain in hearing aid based on loudness judgement using continuous discourse presented at conversational speech level

Recommended Workflow:

M4-Method: Acceptance of Bimodal Fitting Workflow

• Each subject was provided with a minimum of two weeks take home experience with the Linx2 9 or Enzo2 9 hearing aid and the CP900 sound processor fitted using the recommended workflow

• Overall satisfaction level obtained comparing the hearing aid fitting (as provided using the loaner hearing aid and workflow) and their own hearing aid fitting at the time of enrolment

• Subjective feedback collected to explore the potential fine-tuning refinements that might improve satisfaction from that reported from direct application of the bimodal fitting workflow

M4-Results: Acceptance of Bimodal Fitting Workflow

• 16/17 subjects were satisfied with the

bimodal fitting workflow after take-home

use, which included individual fine-

tuning.

• 12 of the subjects reported that they

were ‘very satisfied’ with the fitting, and

4 reported being ‘somewhat satisfied’.

• 1 subject reported being neither

satisfied nor dissatisfied with the fitting.

M4-Results: Acceptance of Bimodal Fitting Workflow

Analysis of the fine-tuning adjustments indicated that:

• Three subjects reported preference for the hearing aid to be louder than the sound processor, ie. bimodal balance was notpreferred

• Two subjects had a frequency response in their own hearing aid that differed substantially from NAL-NL2. They reported being ‘somewhat satisfied’ with the workflow, may have benefited from further fine-tuning to match their own hearing aids more closely.

• One subject who reported being neither satisfied or dissatisfied had experienced feedback problems. Was unavailable for further appointments to trial a more occluding mould.

Theresa Ching 2001







programs matched




Bimodal benefit



need adjustments or

complex loudness


Simple LB as good as complex.

Maybe not needed at all?

Flow well accepted and easy to use

Balancing not preferred by all


Not preferred

Conclusions (M1,M2,M3,M4, Erasmus)

• NAL-NL2 gives suitable amplification (M1,M4, Erasmus)

• Loudness balancing only gives small correction (M3,

Erasmus)

• Complex loudness balancing (frequency specific and/or

multi-level) no benefit over simple (M3,Erasmus)

• No difference in speech understanding or localization

between the approaches (M3, Erasmus)

• No direct evidence that we need loudness balancing at all

(M3, Erasmus)

• The majority subjects were satisfied with the fitting

generated using the bimodal fitting workflow. (M4)

Acknowledgements

• Resound: Astrid Haastrup, Chantal Crins, Tammy Stender

• Erasmus: Jantien Vroegop, Andre Goedegebure

• Cochlear: Ruth English, Kerrie Plant, Birgit Philips

• Publications:

– English et al. 2016, International Journal of Audiology

– Vroegop et al. 2016, submitted Audiology&Neurotology

evidence-based bimodal fitting bas van dijk · final evaluation of fitting flow bimodal benefit...

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