Do digital hearing aid users benefit from using an fm system in class?

Do digital hearing aid Do digital hearing aid users benefit from using users benefit from using an fm system in class?an fm system in class?

YES !

Wave 4 SFR 17/05/04

fm Advantage: new fm Advantage: new procedures procedures

Digital or analogue ?

Whether the hearing aid is digital or analogue is not important, the relevant factor is whether the hearing aid is operating in linear or non linear mode

fmAdvantagefmAdvantage

Motivated by the wish to ensure better fmAdvantage in classrooms

Motivated by the wish to maximise the benefits of fm use by utilising the way the DSP hearing aids work to obtain a beneficial s/n ratio

Lets consider WDRC aids

Wide Dynamic Range Compression

Linear hearing aidCombined mode

Teacher’s voice

Child and classroom voices

Child’s ear

Teacher

Classroom noise

Child

FM advantage lost

Traditional equal output Traditional equal output balancing approach (65/75)balancing approach (65/75)

75dB SPL

60dB SPL

65dB SPL 105dB SPL

110dB SPL

Can the child hear the teacher clearly?

FM signal enters before any DSP, in parallel with the microphone input

The loudest input will drive the compressor

Design of DSP hearing aidsDesign of DSP hearing aids

H.A. MIC

F.M.

INPUT

A/D DSP D/A REC.> > >INPUT

Non- Linear hearing aidCombined mode

Teacher’s voice

Child and classroom voices

Child’s ear

Teacher

Classroom noise

Child

FM advantage preserved

FM advantage approach (65/65)FM advantage approach (65/65)

How do you currently How do you currently balance an FM System?balance an FM System?

Non linear test levelsNon linear test levels

65dB SPL for the hearing aid

65dB SPL for the fm radio system

80dB SPL – the reality part of the test, will we get an fm advantage?

General assumptionsGeneral assumptions

The hearing aid(s) have been separately assessed as working normally

The hearing aid(s) are recognised as being correctly fitted for the user

The fm Advantage setting up procedures are carried out with the hearing aid left at the normal user settings

Before you start ………Before you start ……… Understand the different programmes

and ask which hearing aid programme is intended for fm use?

Listen to the whole system (FM + hearing aid) before you carry out the fm advantage procedures

Set the test box is to display output Use a lapel microphone for the

procedure

MLx useMLx use It may sometimes be the case that

“transparency” with MLx and the HA may not be achieved. However, it is more likely to be achieved with a Phonak transmitter (eg. Campus-S or HandiMic).

The FM advantage with MLx will vary between hearing aids (as it will with conventional fm systems), and each aid to be used with MLx should therefore be individually assessed before fitting.

MLx use cont…MLx use cont… Some DSP aids will only work in

FM+M mode, regardless of how the switch is set on the MLx. There is quite often a better performance ( approx 5dB) on the FM+M setting.

MLx-SMLx-S

Programmable version of MLx Programming requires PC, Hi-Pro

and ‘Toaster’ Presently will be programmed at

factory on instruction Designed for use with “Wall Pilot” Swivelling Pins

LexisLexis

Collaboration by Oticon, Starkey Bernafon and Phonic Ear

Trim pot on the side of receiver which allows adjustment of the response

14 dB range Fixed channels Swivelling pins

InterferenceInterferenceRef: BAEA website/newsletter:

“DSP Hearing aids, personal FM systems and interference: is there a problem?” G. Pont

Also submitted to Ear & Hearing

Summary: As with some CI processors, DSP hearing aids can cause interference to personal fm systems. On the present NHS contract, some aids are “clean” others have quite high levels of interference. We are in dialogue with NHS supplies & manufacturers on this issue.

Practical SessionPractical Session

Listen to FM system with aid of choice (WDRC)

Follow FM Advantage procedure (see booklet, page 5) using Genie and FP35

Choice of MLx, MLx-S or Lexis Listen to system Check for transparency