REM Quick Reference (Key Concepts and Acronyms)

REM ACRONYMS AND CORE IDEAS

  • REM (Real Ear Measurements): objective measures of acoustical output at the tympanic membrane (TM).

  • Scales: REM can be interpreted on the SPL scale (absolute output) or the HL scale (hearing level).

  • Key relationships help interpret how the signal is transformed from input to TM:

    • REUR = Real Ear Unaided Response (absolute SPL at TM with open ear)

    • REUG = Real Ear Unaided Gain (gain from pinna/ear canal/head diffraction in an open ear canal)

    • Gain definition: G/R = gain = output level − input level

    • REUR − Input = REUG → REUR = Input + REUG

  • Occluded measures (vent/dome effects):

    • REOR = Real Ear Occluded Response (SPL at TM with ear canal occluded)

    • REOG = Real Ear Occluded Gain (attenuation due to occlusion/insertion of earmold or dome)

  • Aided measures:

    • REAR = Real Ear Aided Response (output at TM with hearing aid on)

    • REIG = Real Ear Insertion Gain (gain added to overcome insertion loss)

    • REIG relationships:

    • REIG=REAR−REURREIG = REAR - REUR

    • REIG=REAG−REUGREIG = REAG - REUG

  • Maximum output measures:

    • MPO / RESR / REAR85-90: Real Ear Saturation / maximum power output

    • REAR85/90 = MPO (the output at the TM for loud sounds)

  • Coupler-based measures:

    • RECD = Real Ear to Coupler Difference (difference between 2cc coupler SPL and real ear SPL for a given aid/earmold)

  • REDD: Real Ear to Dial Difference

    • Measures the difference between the audiometer dial (HL) and the actual SPL at the eardrum when headphones are used

  • Purpose of REM

    • Improve prescriptive fitting accuracy (e.g., DSL, NAL-NL2 targets)

    • Confirm vent/dome effects, comfort, and audibility across frequencies

    • Enable preprogramming in a test box via RECD without patient present

REAL EAR MEASUREMENTS: SCALES AND PRACTICE

  • SPL vs HL:

    • REM can report in SPL(absolute dB SPL at TM) or HL (targeted sensation level framework)

  • Common resonant frequencies:

    • Average adult ear canal resonance around 2700Hz (2.7 kHz)

    • Acceptable peak resonance range for adults: 2000-4000Hz

  • Open ear canal resonance: REUR measures absolute SPL; REUG measures open-ear gain from ear anatomy

REUR AND REUG: OPEN-EAR MEASUREMENTS

  • REUR: Absolute SPL at TM for an open ear canal

  • REUG: Gain produced by ear anatomy in an open ear canal

  • Formula:

    • REUG = REUR - Input Level

    • REUR = REUG + Input Level

  • Why measure REUR/REUG?

    • Improves prescriptive fitting accuracy

    • Reflects individual ear canal volume, shape, age, genetics, and anatomy

    • Detects probe occlusion (cerumen blockage)

REOR AND REOG: OCCLUDED MEASUREMENTS

  • REOR: SPL at TM when ear canal is occluded (vent blocked)

  • REOG: Degree of attenuation when the hearing aid is inserted and turned off (insertion loss due to occlusion)

  • Practical notes:

    • Used to estimate vent effects and insertion loss with different vent sizes/domes

    • Helps predict low-frequency (LF) release or attenuation caused by vents and domes

  • Vent effects:

    • LF release occurs when vent allows low-frequency energy to escape; larger vents typically increase LF release

  • Standing waves:

    • Earmold vent can create standing waves, causing peaks/dips in low to mid frequencies due to vent resonances

OPEN vs OCCLUDED VENT EFFECTS AND DOME FIT

  • Dome-fit and vent selection influence LF output and overall gain

  • Large/open domes can be acoustically transparent; closed or power domes may require LF gain adjustments

  • Important clinical point:

    • Vent effects may be larger than expected if the dome is too small for the ear canal

REAR: REAL EAR AIDED RESPONSE

  • REAR: Absolute aided output and frequency response with the hearing aid on

  • Purpose:

    • Verify that the fitting achieves the prescribed gain/output (e.g., DSL targets via REAR)

    • Consider ear canal resonances when shaping targets for different populations (adult, pediatric, perforations, etc.)

  • Key notes:

    • REAR is affected by venting; if vented, you may need stored calibration in some setups

    • REAR helps assess how the device actually delivers the target amplification in the ear

REAR AND DSL/NAL TARGETS: INSERTION GAIN APPROACH

  • DSL/NAL targets rely on REAR to confirm desired gain/output in the ear canal

  • REAR-based fitting accounts for ear canal resonance to ensure appropriate audibility without over amplification

  • Typical resonance considerations:

    • Average adult peak ~2000-4000HzHz}</span><br>;differentanatomiesshiftpeaks(e.g.,pediatricorperforationcases)</p></li></ul></li></ul><h3id="f2f3bce1−4f72−41c2−8b84−71c08ce4a955"data−toc−id="f2f3bce1−4f72−41c2−8b84−71c08ce4a955"collapsed="false"seolevelmigrated="true">REARINSERTIONDEPTHFORRICDEVICES</h3><ul><li><p>RealEarAidedResponsevarieswithinsertiondepthofthereceiverintotheearcanal</p></li><li><p>Deeperinsertiongenerallyincreasesmid/high−frequencygain(approximatetrendshowninpractice)</p></li><li><p>Clinicallyadjustdepthtobalancecomfortandaudibilityacrossfrequencies</p></li></ul><h3id="e0aea838−d001−4043−b330−bc432dfe82ed"data−toc−id="e0aea838−d001−4043−b330−bc432dfe82ed"collapsed="false"seolevelmigrated="true">REIG:INSERTIONGAINOVERCOMEINSERTIONLOSS</h3><ul><li><p>REIGmeasuresthegainaddedtoovercomeinsertionlossduetoocclusionorearmold</p></li><li><p>Formula:</p><ul><li><p></span><br>; different anatomies shift peaks (e.g., pediatric or perforation cases)</p></li></ul></li></ul><h3 id="f2f3bce1-4f72-41c2-8b84-71c08ce4a955" data-toc-id="f2f3bce1-4f72-41c2-8b84-71c08ce4a955" collapsed="false" seolevelmigrated="true">REAR INSERTION DEPTH FOR RIC DEVICES</h3><ul><li><p>Real Ear Aided Response varies with insertion depth of the receiver into the ear canal</p></li><li><p>Deeper insertion generally increases mid/high-frequency gain (approximate trend shown in practice)</p></li><li><p>Clinically adjust depth to balance comfort and audibility across frequencies</p></li></ul><h3 id="e0aea838-d001-4043-b330-bc432dfe82ed" data-toc-id="e0aea838-d001-4043-b330-bc432dfe82ed" collapsed="false" seolevelmigrated="true">REIG: INSERTION GAIN OVERCOME INSERTION LOSS</h3><ul><li><p>REIG measures the gain added to overcome insertion loss due to occlusion or earmold</p></li><li><p>Formula:</p><ul><li><p>REIG = REAR - REUR</p></li></ul></li><li><p>Practicaluse:</p><ul><li><p>Ensuretheaidedgainmatchestargetinsertiongain(NAL−NL2,DSL)acrossfrequencies</p></li><li><p>REMsystemsmaycalculateREIGautomaticallyanddisplayit</p></li></ul></li></ul><h3id="c923669f−abb1−4b4e−b37d−00575824bf3a"data−toc−id="c923669f−abb1−4b4e−b37d−00575824bf3a"collapsed="false"seolevelmigrated="true">WHYWEMEASUREREIG</h3><ul><li><p>NAL−NL2reliesonREIGtomaximizespeechintelligibilityatcomfortableloudness</p></li><li><p>REIGfocusesoninsertiongain(gainintheearcanalrelativetounaidedear)ratherthanabsoluteSPLatTM</p></li><li><p>Thishelpsensurethedevicedeliversintendedamplificationdespiteearcanalresonances</p></li></ul><h3id="44b0068b−7026−4b6c−9454−81700fef28e6"data−toc−id="44b0068b−7026−4b6c−9454−81700fef28e6"collapsed="false"seolevelmigrated="true">MPO/RESR/REAR85/90:MAXOUTPUTMEASURES</h3><ul><li><p>MPO(MaximumPowerOutput)orRESR/REAR85/90:</p><ul><li><p>MeasuresthemaximumSPLthehearingaidcandeliverattheTMforloudsounds</p></li></ul></li><li><p>Measurementmethods:</p><ul><li><p>Type1inputsignalat90dB,comparedtoLDLdata(earleveltechnique)</p></li><li><p>For85dBinput,comparedtoLDLdata(in−situapproach)</p></li></ul></li><li><p>Purpose:</p><ul><li><p>EnsureMPOsettingsdonotexceedloudnessdiscomfortlevels</p></li><li><p>Confirmdevicecandeliverstrongoutputwithoutdistortionordiscomfort</p></li></ul></li></ul><h3id="20e2e507−be88−4540−a223−8978a94556cc"data−toc−id="20e2e507−be88−4540−a223−8978a94556cc"collapsed="false"seolevelmigrated="true">RECD:REALEARTOCOUPLERDIFFERENCE</h3><ul><li><p>RECDquantifiestheacousticdifferencebetweena2cccouplerandtherealearcanalforagivenaid/earmold</p></li><li><p>Use:</p><ul><li><p>Convertreal−earmeasurementstoatest−box(coupler)frameworkforinitialprogramming</p></li><li><p>Applytopersonalizecouplingfactorsandimproveaccuracyofbox−basedverification</p></li></ul></li><li><p>Importantnote:</p><ul><li><p>VenteffectisnotcapturedbyRECD</p></li></ul></li></ul><h3id="bc679105−54e9−4ecb−8d8f−59a884b7e32c"data−toc−id="bc679105−54e9−4ecb−8d8f−59a884b7e32c"collapsed="false"seolevelmigrated="true">HOWISRECDMEASURED?</h3><ul><li><p>Steps:</p><ul><li><p>Attachcouplertocouplermicrophone;attachRECDtransducertocoupler</p></li><li><p>Generatesignalandstorecouplerresponse</p></li><li><p>ConductREMwiththepatient:otoscopicexam,placeprobeneareardrum,placefoameartiporearmoldtubinginear</p></li><li><p>Generatesamesignalascouplermeasurement</p></li><li><p>SubtractstoredcouplerresponsefromREMtoobtainRECD</p></li></ul></li><li><p>Outcome:</p><ul><li><p>Providesconversionfactorstopredictreal−earSPLfromcouplermeasurements</p></li></ul></li></ul><h3id="47cef1ef−1230−4659−8feb−ecd250fb13cf"data−toc−id="47cef1ef−1230−4659−8feb−ecd250fb13cf"collapsed="false"seolevelmigrated="true">REDD:REALEARTODIALDIFFERENCE</h3><ul><li><p>REDDexplainsthedifferencebetweentheaudiometerdialsetting(HL)andtheactualSPLreachingtheTMwhenheadphonesareused</p></li><li><p>Use:</p><ul><li><p>ConstructSPL−O−gramSforfittingmethodsthatuseheadphones</p></li><li><p>REDDvaluesareaccuratewithinabout2.3dBoftruereal−earSPL(Scollieetal.,1998)</p></li></ul></li><li><p>Measurementmethod:</p><ul><li><p>Placeprobeinearcanal;placesameheadphonesusedforaudiometry</p></li><li><p>Presenta70dBHLtone;measureSPLinearcanal</p></li><li><p>Compute</p></li></ul></li><li><p>Practical use:</p><ul><li><p>Ensure the aided gain matches target insertion gain (NAL-NL2, DSL) across frequencies</p></li><li><p>REM systems may calculate REIG automatically and display it</p></li></ul></li></ul><h3 id="c923669f-abb1-4b4e-b37d-00575824bf3a" data-toc-id="c923669f-abb1-4b4e-b37d-00575824bf3a" collapsed="false" seolevelmigrated="true">WHY WE MEASURE REIG</h3><ul><li><p>NAL-NL2 relies on REIG to maximize speech intelligibility at comfortable loudness</p></li><li><p>REIG focuses on insertion gain (gain in the ear canal relative to unaided ear) rather than absolute SPL at TM</p></li><li><p>This helps ensure the device delivers intended amplification despite ear canal resonances</p></li></ul><h3 id="44b0068b-7026-4b6c-9454-81700fef28e6" data-toc-id="44b0068b-7026-4b6c-9454-81700fef28e6" collapsed="false" seolevelmigrated="true">MPO/RESR/REAR85/90: MAX OUTPUT MEASURES</h3><ul><li><p>MPO (Maximum Power Output) or RESR/REAR85/90:</p><ul><li><p>Measures the maximum SPL the hearing aid can deliver at the TM for loud sounds</p></li></ul></li><li><p>Measurement methods:</p><ul><li><p>Type 1 input signal at 90 dB, compared to LDL data (ear level technique)</p></li><li><p>For 85 dB input, compared to LDL data (in-situ approach)</p></li></ul></li><li><p>Purpose:</p><ul><li><p>Ensure MPO settings do not exceed loudness discomfort levels</p></li><li><p>Confirm device can deliver strong output without distortion or discomfort</p></li></ul></li></ul><h3 id="20e2e507-be88-4540-a223-8978a94556cc" data-toc-id="20e2e507-be88-4540-a223-8978a94556cc" collapsed="false" seolevelmigrated="true">RECD: REAL EAR TO COUPLER DIFFERENCE</h3><ul><li><p>RECD quantifies the acoustic difference between a 2cc coupler and the real ear canal for a given aid/earmold</p></li><li><p>Use:</p><ul><li><p>Convert real-ear measurements to a test-box (coupler) framework for initial programming</p></li><li><p>Apply to personalize coupling factors and improve accuracy of box-based verification</p></li></ul></li><li><p>Important note:</p><ul><li><p>Vent effect is not captured by RECD</p></li></ul></li></ul><h3 id="bc679105-54e9-4ecb-8d8f-59a884b7e32c" data-toc-id="bc679105-54e9-4ecb-8d8f-59a884b7e32c" collapsed="false" seolevelmigrated="true">HOW IS RECD MEASURED?</h3><ul><li><p>Steps:</p><ul><li><p>Attach coupler to coupler microphone; attach RECD transducer to coupler</p></li><li><p>Generate signal and store coupler response</p></li><li><p>Conduct REM with the patient: otoscopic exam, place probe near eardrum, place foam ear tip or earmold tubing in ear</p></li><li><p>Generate same signal as coupler measurement</p></li><li><p>Subtract stored coupler response from REM to obtain RECD</p></li></ul></li><li><p>Outcome:</p><ul><li><p>Provides conversion factors to predict real-ear SPL from coupler measurements</p></li></ul></li></ul><h3 id="47cef1ef-1230-4659-8feb-ecd250fb13cf" data-toc-id="47cef1ef-1230-4659-8feb-ecd250fb13cf" collapsed="false" seolevelmigrated="true">REDD: REAL EAR TO DIAL DIFFERENCE</h3><ul><li><p>REDD explains the difference between the audiometer dial setting (HL) and the actual SPL reaching the TM when headphones are used</p></li><li><p>Use:</p><ul><li><p>Construct SPL-O-gramS for fitting methods that use headphones</p></li><li><p>REDD values are accurate within about 2.3dB of true real-ear SPL (Scollie et al., 1998)</p></li></ul></li><li><p>Measurement method:</p><ul><li><p>Place probe in ear canal; place same headphones used for audiometry</p></li><li><p>Present a 70 dB HL tone; measure SPL in ear canal</p></li><li><p>ComputeREDD = SPL_{ ext{ear}} - HL$$ for each frequency

SUMMARY OF KEY RELATIONSHIPS

  • REUR: natural ear resonance (open ear)

  • REOR: insertion loss due to occlusion (vent/dome effects)

  • REAR: output with aid on

  • REIG: insertion gain to match targets

  • MPO/RESR/REAR85/90: maximum output capability

  • RECD: coupler-to-real-ear difference for box-based fitting; vent not included

  • REDD: headphones-to-ear SPL difference from dial settings

PRACTICAL CHECKLIST FOR COMPETENCY

  • Identify each acronym and its clinical usefulness

  • Perform the measurement steps for REUR, REOG/REOR, REAR, REIG, RECD, and REDD with proper probe placement and repeatable positioning

  • Compare REAR to DSL/NAL targets and adjust gain/output accordingly

  • Consider vent effects, dome type, and insertion depth when interpreting results

  • Use RECD to translate HL targets into SPL for box-based verification; account for ear canal variability

CRITICAL CONCEPTS TO REMEMBER

  • REUR and REUG provide baseline open-ear acoustics and gain

  • Occluded measures (REOR/REOG) reveal vent/dome influence and insertion loss

  • REAR and REIG quantify actual aid performance in the ear canal

  • MPO/RESR define device's loudness limits in situ

  • RECD enables accurate HL to SPL conversion for personalized fittings

  • REDD allows headphone-based audiometry to be aligned with real-ear outputs