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