In Situ Versus Coupler Verification Working Smarter !

RECD Refresher Course17th November 2004

In Situ Versus CouplerIn Situ Versus CouplerVerificationVerification

Working Smarter !Working Smarter !

Ed BrownEd Brown

Consultant Audiological ScientistConsultant Audiological Scientist

MCHASMCHAS

University of ManchesterUniversity of Manchester


Audiometry (Custom moulds & Inserts)Audiometry (Custom moulds & Inserts) HA PrescriptionHA Prescription Fine Tuning +++ Fine Tuning +++

2 ears, 4 levels, 1 restless child In Situ HA Verification (50, 65, 80, 90)In Situ HA Verification (50, 65, 80, 90)

Comfortable verifying at 80 and 90 in real ear ? Speech TestingSpeech Testing Programs, Use, Parent/Child InstructionPrograms, Use, Parent/Child Instruction Frequency Response CurvesFrequency Response Curves

What Needs to be Done ?What Needs to be Done ?


Listening/Comfort CheckListening/Comfort Check Other ProgrammesOther Programmes Volume ControlVolume Control

Disabled, enabled, what range ? Conductive LossConductive Loss

How much gain, what strategy ? New EarmouldsNew Earmoulds Completion/Collation of QuestionnairesCompletion/Collation of Questionnaires FM Balance/AdvantageFM Balance/Advantage ……and then the PC crashesand then the PC crashes

What Else Needs to be Done ?What Else Needs to be Done ?


How many staff involved in a child’s review ?How many staff involved in a child’s review ? What are their skills, experience ?What are their skills, experience ? Do all staff in department work with children ?Do all staff in department work with children ? How long is your review appointment ?How long is your review appointment ? Variable in the UKVariable in the UK

1 person 40 minutes2 persons 2 hours

MCHAS recommend 2 persons 90 minutesMCHAS recommend 2 persons 90 minutes

What Resources Do You Have?What Resources Do You Have?


So what are you going to do?So what are you going to do?


One measurement not fourOne measurement not four Child does not need to be present once measuredChild does not need to be present once measured Can be measured/recorded elsewhereCan be measured/recorded elsewhere Gives the option to multitaskGives the option to multitask Save the RECDSave the RECD

You can build/rebuild (almost) everything from this Compile your own normative dataCompile your own normative data

Improve accuracy of “first fits” Easy to monitor changes in canal acousticsEasy to monitor changes in canal acoustics Pattern recognitionPattern recognition

RECD AdvantagesRECD Advantages


RECD DefinitionRECD Definition

Difference between the SPL measured in the real ear and SPL measured in a 2 cc coupler.

- =


Are RECDs Valid ?Are RECDs Valid ?

YesYes The RECD/REDD will take you, on average, to The RECD/REDD will take you, on average, to

within 1 dB of the ear canal SPLwithin 1 dB of the ear canal SPL The error will never be more than 5 dB (in 95% The error will never be more than 5 dB (in 95%

of subjects)of subjects)

References: Munro KJ, Davis J. Deriving the real-ear SPL of audiometric data using the "coupler to dial

difference" and the "real ear to coupler difference". Ear and Hearing 2003;24:100-10. Munro KJ, Hatton N. Customized acoustic transform functions and their accuracy at

predicting real-ear hearing aid performance. Ear and Hearing 2000;21:59-69.


What about Transducer Type ?What about Transducer Type ?

There are issues regarding transducer There are issues regarding transducer type/methodology when measuring RECDtype/methodology when measuring RECD

There are differences between using an Insert There are differences between using an Insert Phone and Hearing InstrumentPhone and Hearing InstrumentTo do with acoustic impedancesMost pronounce around 2k Hz

May need to measure two RECDs ?May need to measure two RECDs ?References:

Munro KJ, Salisbury VA. Is the real-ear to coupler difference independent of the measurement earphone? International Journal of Audiology 2002; 41:408-13.

Munro KJ, Toal S. Measuring the RECD Transfer function with and Insert and a hearing instrument. Are they the same thing ?. 2004. In Phonak Focus 33.


Measure Each Ear ?Measure Each Ear ?

Reference: Munro KJ, Buttfield, L. A comparison of real ear to coupler difference values in the right and left ear of adults using 3 earmould configurations, in press,

Ear and Hearing

Co operation may be limitedCo operation may be limited Use one RECD for both ears Use one RECD for both ears In general differences are less than 3 dBIn general differences are less than 3 dB

Proviso: no significant wax, normal middle ear function

Probably better than using predicted dataProbably better than using predicted data


How Often ?How Often ?

Reference: Bagatto MP. Optimising your RECD Measurements. Hearing Journal 20001;54:32, 34-36

Biggest changes occur within first 2 years of lifeBiggest changes occur within first 2 years of lifeRECD can be 20-30 dB for 1 month oldNot a difficult (relatively) age to measure

Ideally should be measured whenever new Ideally should be measured whenever new earmoulds providedearmoulds provided

In practiceIn practiceEvery 3 months until 2 years of age ?Then every 6 months until 5 years of age ?


RECD on InfantRECD on Infant


Effect of OMEEffect of OME


So…So…

There are limitations to an RECD/Coupler There are limitations to an RECD/Coupler compared to In Situ Approach…compared to In Situ Approach…

……but the clinical advantage for most children but the clinical advantage for most children probably outweighs thisprobably outweighs this

RECDs are potentially useful for all childrenRECDs are potentially useful for all childrenAdults also ?

On going researchOn going research Measure In Situ response if you canMeasure In Situ response if you can

At subsequent review appointment ?


DSP Exchange (90 min)DSP Exchange (90 min)

Pre-Visit (Audio on NOAH, LIFE & LSQ available (on PMS))Pre-Visit (Audio on NOAH, LIFE & LSQ available (on PMS))

““First Fit” aids, previous audiometry, predicted RECDFirst Fit” aids, previous audiometry, predicted RECD

““Insert Phone Audiometry (Custom Earmoulds & Inserts)Insert Phone Audiometry (Custom Earmoulds & Inserts)

Measure RECDsMeasure RECDs

Speech TestingSpeech Testing

Questionnaire CompletionQuestionnaire Completion

Prescription & Verification (2cc Coupler)Prescription & Verification (2cc Coupler)

Frequency Response CurvesFrequency Response Curves

Initial Evaluation, Hearing Instrument Orientation ProgrammeInitial Evaluation, Hearing Instrument Orientation Programme

Assess VC, Assess VC, Processing and Processing and Program needProgram need


In SummaryIn SummaryThe Clinical AdvantagesThe Clinical Advantages

Can be used to improve accuracy of some Can be used to improve accuracy of some manufacturer “first fit” proceduresmanufacturer “first fit” procedures

Only require co-operation for one measurement Only require co-operation for one measurement rather than multiple real ear measurementsrather than multiple real ear measurements

Prescription can be verified in coupler without Prescription can be verified in coupler without child present and/or “off line”child present and/or “off line”

More effective use of clinic appointment timeMore effective use of clinic appointment time Skills (e.g. insert PTA & RECD versus full Skills (e.g. insert PTA & RECD versus full

prescription procedureprescription procedure

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In Situ Versus Coupler Verification Working Smarter !