Selection of Hearing Aid

An Overview about Selection of Hearing Aid including Electroacoustic and Non-Electroacoustic Considerations.

1. SELECTION OF HEARING AID
Dr. Shazia Tahira
Audiology & Speech-Language Pathology
University of Karachi

2. SELECTION OF HEARING AID
Selection of hearing aid is a process in which an audiologist recommends the most
suitable hearing aid toa patient who is found to be a candidate for hearing
aid.Hearing aid selection follows the clinician’s assessment of apatient’scandidacy for
amplification, and precedes the hearingaid fitting process.Theclinicalchallenge is
toweigh the manyfactors in theselectionprocess toachieve anoptimum fitting.
It is essential that the audiologist, patient, and family/caregivers combine their efforts to
achieve optimum outcome of the hearing aid selection process. The audiologist has sole
responsibility forpreselection of the appropriate electroacoustic characteristics of the
hearing aids. Decisions about the nonelectroacoustic characteristics of the hearing aid
(style, features, options, etc.) should be based on the management plan/needs
assessment and the ongoing interaction with the patient.

3. FACTORS TO CONSIDER DURING SELECTION OF HEARING AID
During selection of hearing aid, the clinician needs to consider various factors
➢COSMETIC CONSIDERATIONS
➢HEARING AID STYLE FOR CHILDREN
➢EARMOLD SELECTION
➢EARMOLD SELECTION IN CHILDREN
➢ANY ABNORMALITY IN SHAPE AND SIZE OF EAR AND EAR CANAL
➢MANUAL DEXTERITY &MENTAL ACUITYFOR HANDLING
➢PRESENCE OF ADDITIONAL FEATURES
➢LESS COMMON STYLES OFHEARING AIDS
➢BINAURAL VS. MONAURAL FITTING
➢MANAGING UNILATERAL HEARING LOSS
➢HEARING AID TECHNOLOGY
➢FINANCIAL CONSIDERATIONS
➢REQUIRED ELECTROACOUSTIC CHARACTERISTICS

4. COSMETIC CONSIDERATIONS
Hearing aids come in avariety of styles having different sizes and
colors. Mostpeople are sensitive about theirhearing aids being
visible and insiston the most discreet option.
IIC CIC ITC ITE RIC OpenFit
BTE
BTE
Fits deeply
inside ear
canal
Fits inside ear
canal
Fits partly in
the ear canal
Fills Outer Ear
(Concha)
Completely
(Full Shell) or
Only Lower
Half (Half
Shell)
Receiverin
the
earcanal.
Tinywire
connects the
piecebehind
theearto
the
receiver
Thin tube
behind the
ear,
receiverin
the ear canal
or behind the
earwith an
open dome
in the ear.
A behind-the-
earreceiver
tube
connects
toear mold
in ear canal
Smallest, least
visible
Very Small,
Much Less
visible
Less visible
than larger
styles
More
visiblethan
smaller styles
A less
visiblebehind
-the-ear
portion
Often visibleMuch larger
style, much
visible
newer mini
BTE less visible

5. IIC CIC ITC ITE RIC Open Fit BTE BTE
Invisible in Canal -Completely in Canal -In the Canal -In the Ear -Receiver in the Canal -Open Fit Behind the Ear -Behind the Ear
COMMON STYLES OF HEARING AID

6. HEARING AID STYLE FOR CHILDREN
A Behind the Ear Hearing Aid (BTE) with earmold style is
commonly used for children because BTE is larger in size and
easier to handle,BTE earmold can be replaced as the child
grows.BTE stylescan fit any type of hearing loss, from mild to
profound and is capable of more amplification than other
styles, as because of their larger size, they can generally
havemore features, controls and battery power than any other
style of hearing aid.

7. EARMOLD SELECTION
Throughotoscopy and generalexamination of external ear and ear canal, an
audiologistneeds to determine whether a person’s ear canalanatomy allows for a
specific choiceofcustom-made hearing aid or earmoldstyle.Earmolds must be
comfortable and easy to insert and remove. BTEsor custom hearing aids
usuallyrequirecustom earmolds . On the other hand, some hearing aids like Open
Fit BTE or RICmay be connectedto the ear using non custom “domes.”
IIC CIC ITC ITE RIC Open Fit BTE BTE
Custom
Molded
Hearing Aid
Custom
Molded
Hearing Aid
Custom
Molded
Hearing Aid
Custom
Molded
Hearing Aid
NonCustom
Open Dome
orCustom
Earmold
Non Custom
Open Dome
Custom
Earmold

8. EARMOLD SELECTION IN CHILDREN
A well-fitted, comfortable soft earmold or a soft customcasing fora
receiver-in-the-earisa key requirement formost children’shearing aid
fittings. Either of theserequiresthat an accurate earimpression is taken and
that earmoldfit is closelymonitored overtime, particularly during ages 0to 2,
when rapid growth of theexternalear is expected. Thiscontinues ata
slower rate to aboutage 5 or 6.
Colorful earmoldswith sparkles, swirls, and picturesof favoritecharacters are
all options that youngchildren liketo choose.Teens and tweens may
continue to choose brightcolors ormaywish to change styles and colors to
minimizecontrast withskin and hair tones. Mattetubing or receiver in-the-ear
optionsmay facilitate continued acceptance ofBTE ormini-BTE styles
andtherefore maintain options forhigh-gain fitting

9. ANY ABNORMALITY IN SHAPE AND SIZE OF
EAR AND EAR CANAL
Not all ear canals are big enough toaccommodate the components
that needto fit into the shell of a custom-madehearing aid.
Anatomical features suchas the tragus or antitragus, may
beprominent and interfere with the fit of acustom-made hearing
aid, such asplacement of the controls on the faceplate of a custom-
made hearing aid.sometimes an ear canal issimply too small to
accommodate components in the shell of a custom made hearing
aid.
If there are malformations of the ear e.g. an absent pinna, a stenotic
ear canal, oratresia, then other options such as a surgically
implantedBAHA (Bone-Anchored Hearing Aid) should be considered.
A small titanium implant (3-4 mm) issurgically embedded into the
mastoidbonebehind theearwith a smallabutmentexposed
outsidethe skin. The BAHA sound processor is placedon
thisabutmentandtransmitssoundvibrationsto the external
abutment of the titaniumimplant. The implant vibrates the mastoid
bone and inner ear, which stimulatethenerve fibersof the inner ear
and allow hearing bypassing outer and middle ear. Children under
the age of 5 typically wear the BAHA device on a soft band without
surgical implant. This can be worn from the age of one month.

10. Condition Hearing Aid Options
Lack of Pinna Bone-Anchored
Hearing Aid (BAHA)
Lack of Ear Canal Bone-Anchored
Hearing Aid (BAHA)
Small Pinna ITE, ITC, CIC
Draining Ear
(treated)
Open Fit BTE
Draining Ear
(chronic)
Bone-Anchored
Hearing Aid (BAHA)
Severe
Dermatitis(treated)
Hypoallergenic Mold
Tenderness in canal
wall
Soft Material for
Mold
Tenderness
inConcha
Soft Mold BTE
Stenosis in Canal Mold or Aid to be
Fitted before
Stenotic Area
Bone-Anchored Hearing Aid

11. MANUAL DEXTERITY &MENTAL ACUITY FORHANDLING
Dexterity, mobility and mental acuity influence selection of hearing
aids especially in younger andolder individuals. Stroke patients,
patients with reducedsensitivity of touch in their fingertips, the
presence of tremors (e.g.,Parkinson disease)and medications can
also affect manual dexterity.The smaller the hearingaid, the smaller
the controls and thebatteries. Small aids(custom-made or mini-BTE’s)
are not suitable forpediatricor geriatric patients. Traditional BTEs are
mostly recommended for pediatric andgeriatric patients.
The insertion, removal, and operation of various hearing aid styles
must be evaluated carefully by the clinician. A very easy protocol to
incorporate into the selection process is to have the patient operate
a sample hearing aid, use controlsand insert and remove battery.
IIC CIC ITC ITE RIC OpenFitBTE BTE
verysmall
size,problem
fordexterity
verysmall
size,problem
fordexterity
comparatively
small, difficult
toinsertand
remove
largersize
easierto
Insert and
remove
largersize
easierto
insertand
remove
largersize.
easierto
insertand
remove
much larger
size, easierto
insert
andremove

12. PRESENCE OF ADDITIONALFEATURES
Hearing aids having optional features that canassist the patient indifferent communication
situations may be considered. Although there are many such features, a fewof them include
➢Directional Microphoneallows sound comingfrom aspecific direction (usually front) to be
amplified to a greater levelcompared to soundfrom other directions and may help in noisy
environments.
➢Rechargeable BatteriesSome hearing aids have rechargeable batteries making maintenance
easier.
➢T-coil (Telephone Switch)allows to switch from the normal microphone setting to a "T-coil" setting
in order tohear better onthe telephone. In the "T-coil"setting, environmental sounds are
eliminated, and sound is picked up from the telephone. Thisalso turns off themicrophone on
hearing aid so you can talk without your hearing aid don't "whistle."The T-coil works well
inauditoriumsand other places that have an induction loop or FMinstallation. The voice of the
speaker, who can be somedistance away, is amplified significantly more than anybackground
noise. Some hearing aids have a combination "M"(Microphone) / "T" (Telephone) switch so that,
whilelistening with an induction loop, nearby conversation can still be heard.
➢Wireless ConnectivityIncreasingly, hearing aids can wirelessly interface with certain Bluetooth-
compatible devices, such ascellphones, music players,computers and televisions. You may need
to use an intermediary device to pick up the phone orother signal and send it to the hearing aid.

13. CIC ITC ITE RIC BTE
usesverysmall
batteries withshort
battery life
usessmall
batterieswithshort
battery life
uses largerbattery
withlongerbattery
life with option
forrechargeable
batteries
useslargerbattery
withlongerbattery
life with optionfor
rechargeable
batteries
useslargerbattery
withlongest
batterylife
thanother hearing
aids,optionfor
rechargeable
batteries
small size canbe a
problemfor
connectivityto
wirelessdevices
small size canbe a
problemfor
connectivityto
wirelessdevices
likelytohave
connectivity
towirelessdevices
like phones
most likely tocome
withwireless
connectivityto
deviceslike phones
usuallyavailablein
modelswithwireless
connectivity
todevices
oftendoesn't
includeextra
features
includessome extra
features
volumecontrol
availablewith
directional
microphones(two
microphonesfor
betterhearing),
morefeaturesand
usercontrols
hasmanualcontrol
options,
hasdirectional
microphones,
telecoiloptionsare
common
can generallyhouse
morefeatures,
controls thanany
otherstyle
ofhearing aid.
hasdirectional
microphones

14. LESS COMMON STYLES OF HEARING AIDS
➢Body Level or Body-worn Hearing Aids
Body Level aids (BL) consist of a case and an earmold, attached by a
wire. The case contains the electronic amplifier components, controls
and battery, while the earmold typically contains a miniature
loudspeaker. The pocket-sized case is carried in a pocket or on a belt.
Body Level aids (BL) were the first portable electronic hearing aids and
were very popular a few decades back, as they were, at thetime, the
only way to provide powerful amplification and good battery life for
severe and profound hearing loss. As technology in BTEs improved, the
need for body Level Aid decreased sharply. However Body
Levelhearing aids are still produced, because they are less expensive
to buy and batteries used are cheaper AA or AAA types.BL Can
provide high gain and has less chances of acoustic feedback due to
more distance between microphone and receiver. Larger controls
and larger batteries allow old patients to handle BL easily.

15. ➢Spectacle Hearing Aids
Spectacle hearing aids refer to designs where a hearing aid isbuilt into
orattached to the arms or frame of a pair of spectacles as manypeople
have avision as well ashearing impairments orprefer a more cosmetic
appeal of theirhearing aids by beingattached to theirglasses. Some
spectacleaids have directional microphonecapability.These types of
fittings are not popular; as one’s choice of glasses frames andhearingaid
isseverely restricted and when the glasses are removed, the hearingaid
needs to betaken out aswell. Successfulfittings usingspectacle hearing
aids are difficult to achieve.Spectacle aids comeintwoforms.
➢Bone Conduction Spectaclesare recommended for individuals
withconductive hearingloss.Soundsare transmitted via a
receiverattached from the arm of thespectacleswhich are fitted firmly
behind theboneyportion of the skull at theback of theear,
(mastoidprocess) by means of pressure, applied on the
armofthespectacles. The sound is passed from the receiver on the arm
ofthespectaclesto the inner ear (cochlea),via
thebonyportion. Boneconductionaids generally have a poorer high
pitchresponse andare thereforebest usedfor conductive hearing
lossor where itis impractical to fit standardhearingaids.
➢Air Conduction Spectaclesdeliver the sound to the ears via the ear
canal like a traditional hearing aid and can be used forsensorineural
hearing loss. Some models use Receiver in Canal technology whilst others
use Behind the Ear technology attached to thearmor arms
ofthespectaclesand deliver the amplified sound to the ear via a
tubeorearmold.

16. BINAURAL VS. MONAURAL FITTING
➢Binaural Fitting
In most cases, it is usually better to fit a patient binaurally,because bilateral
fittings diminish headshadow effect and lead to binaural fusionandintegration
resulting in a more natural amplified sound, bettersound localization,and
betterspeech understanding especially innoisy listeningconditions.
➢Monaural Fitting
Monauralfittingcanbedonewhenthereisunilateralhearingloss,or
anatomical/structuralmalformations ofone ear.

17. MANAGING UNILATERAL HEARING LOSS
➢Monaural Hearing Aid
If there is hearing left in the affected ear, a unilateral hearing loss can often be treated with amplification by using
a normal hearing aid.
➢CROS Hearing Aids
Whenbetter ear hears normally, a small transmitter microphone, placed behind or insidethe ear that cannot
benefit from a hearing aid, picksup sound andtransfersit wirelessly to a receiver on the betternormal hearing ear
assisting the patient in hearing andunderstandingauditory informationevenwhensoundscome from the side
where they have nohearing.
➢BiCROSHearing Aids
Whenthere is a hearing loss in the better ear, thesmall transmitter placed behind or inside the ear that cannot
benefit from a hearing aidpicks up sound andtransfersit wirelessly to the better ear fitted with a hearing aid that
amplifies soundscomingdirectlyto the better earassisting the patient in hearingandunderstandingauditory
information coming from both better and worsesides.
➢Bone-Anchored Hearing Aid
Bone-Anchored Hearing Aid can be used to treat profound unilateral hearing loss. When the BAHA is implanted
behind the affected ear in patients, the vibration of bone from the BAHA is transmitted to the cochlea of the
opposite ear allowing the perceived sensation of sound from the side of the head with the dead ear.

19. HEARING AID TECHNOLOGY
Select the type oftechnology and features forthehearingaid based on
thetechnology(Analogue/Programmable Analogue/Digital/Non Programmable
Digital)that will best suit thepatient’s hearing loss, lifestyle andcommunication needs.

20. Analog Aids(Traditional Linear Aid)convert sound
waves intoelectrical signals, which are
amplified.Analog hearing aidsmakecontinuous
soundwaves louder. These hearing aids
essentiallyamplify all sounds (e.g., speech and
noise) inthesameway.
Digital Hearing Aidsconvert sound waves
intodigital signals. Computer chips in digitalhearing
aids allow for more complex processing ofsound
during theamplification process. Greater flexibility in
hearing aidprogramming, can bespecially
programmed toamplifysomefrequencies more
than others,sound transmitted canbematched to
theneeds for a specific patternofhearing loss,
adjusting the aid to a user’sneeds andto certain
listeningenvironments
➢Benefits of Digital Signal Processing
Feedbackmanagement,occlusionreduction,
loudness mapping, electronicshaping,expansion
toreduce/eliminate circuit noise for those patients
with normal low-frequency hearing, noise
reductionalgorithms(NR) for improved comfort in
noisy listening situations, multiband processing for
greater precision inshaping the frequency-
gain/output response,
multiplememories(separateprograms/memories
(orautomaticallyswitchingmemories)
Programmable Analog Aids(Digitally Controlled
Analog via computers)havea microchipwhich
allows the aid tohave settings programmed for
different sound frequencies.
Non Programmable Digital Hearing Aidsare
preprogrammed for different sound frequencies
and unlikeprogrammable hearing aids, can't
beprogrammedagain. All thesehearing aidshave
a mode switching function, which can fit for the
different sound environments

21. FINANCIAL CONSIDERATIONS
Consider the patient’s finances and thetype of technology that
the patient canafford.
Hearing aids come indifferent price
ranges and vary from
the most basic technology (most
affordable/entry-level/budget
hearing aids) to advanced techno
logy (most expensive/top-endhearing
aids)
The largest difference betweenAnalog
and Digitalhearing aids iscost.
Becausedigital hearing aidsare more
technologicallyadvanced, they tend
to costmore.
Mostmanufacturers offer avarietyof
hearing aid types (BTE’sandcustom-
made) ofthe sametechnologywithin
the same pricerange. In developing
countriesBTE´sare the mostcommon
andavailable hearing aids
If Binaural fitting is preferable, it'sbetter
to fittwo hearing aids in amore
affordablepricerange, thanone more
expensivehearingaid.

22. REQUIRED ELECTROACOUSTIC CHARACTERISTICS
Electroacoustic Characteristics include gain, maximum output and frequencyresponse required forthe
patient’s hearingloss according tothe audiogram i.e. degree, type,andconfiguration of hearing
loss.Gain, frequency response, and maximum outputare the basic specifications for ahearingaid.
➢Gainrefers to a measure of theoverall degree of amplification and is usually quantifiedeither by the
maximum gain irrespective of frequency,by the average gain at specified frequencies, such as0.5, 1,
and 2 kHz, or by the gain at a single referencefrequency.
➢Frequency Response refers to the shape of thegain requirements across frequency, an important
aspectof which is the required slope in each octave, given bythe differences between required gains
at adjacentoctave test frequencies.
➢Maximum Output refers to thehighest OutputSound Pressure Level (SPL) that the hearing aid can
generate and againcan be quantified by the maximum irrespective offrequency, by an average
across specified frequencies,or by the value at a single reference frequency . Maximum output is
usually measured witha 90 dB SPL input level and is themaximum output Sound Pressure Levelof
thehearing aid in the 2 cm3coupler with a 90 dB Input (OSPL90) and can also be referred to as
Saturated Sound Pressure Level (SSPL)
➢Input-Output Characteristicsare static compression characteristics (compression thresholdand ratio)
or gain for multiple inputs in one ormultiple frequency bands innonlinear signal processing. Although
not extensively validated, several hearing aid selection protocols (e.g., DSL [i/o]) offer assistance in
makingdecisions about input-output characteristics.

23. ➢RealEarMeasurements
The determination of frequency response, gain, and overall output of the hearing aid must
bedecided.In many settings, Real Ear measurements are made to help select the proper
characteristicsof thehearing aid. Specifications of hearing aids from manufacturers are produced
using the ANSIS3.22standards concerning the gain, output, and frequency response of the hearing
aid.Thesemeasurements are made in a 2-cm3 coupler. This coupler is used to simulate the
condition ofthe aidin an ear, but many differences exist between a metal 2-cm3 coupler and the
volume andtexture ofan ear canal and eardrum, and many individual differences exist between
ears. Becauseof thesedifferences, a Real Ear probe-tube measurement is used to reveal the exact
frequencyresponse,gain, and maximum output of thehearing aid in the ear at the site of the
eardrum.
UsingtheRealEarequipment,theaudiologistplacesaprobemicrophoneintotheearcanaland
presentsaknownauditorysignaltothepatient.Theinformationfromthemicrophonewhenthe
stimulusispresentyieldsaRealEarUnaidedResponseorRealEarUnaidedGain(REURorREUG).This
responserevealstheresonatingcharacteristicsoftheearcanalwithouttheaidinplaceandcan
assistinformulatingthebest2-cm3couplerresponseforapatientatthetimeahearingaidis
ordered.AvarietyofprescriptivetechniquesforfittinghearingaidsuseinformationfromRealEar
measures.Oneofthemostpopularprescriptivetechniquesistheproceduredevelopedbythe
NationalAcousticsLaboratory(NAL)inAustraliaforselectinggainandfrequencyresponseofa
hearingaid.TheNALalgorithmisusedtocalculatethemostappropriateRealEargain.Fromthe
algorithm,ahearingaidisselectedwiththerequiredfrequencyresponseandgaincharacteristics,
andcomparisonsaremadebetweenthepredictedgainandtheRealEarmeasurements
obtainedfromthehearing-impairedpatient.

24. Real Ear Aided Response (REAR)or Real Ear Aided Gain (REAG)
is a measure which involves the hearing aidbeing positioned
on the ear as per normal use and the probe microphone
inserted. This allows measurement of the hearing aid
amplification effect within the patients’ ear.
To get the value of Real Ear Insertion Gain (REIG), the value of
Real Ear unaided response or Real Ear Unaided Gain (REUR or
REUG) is subtracted from Real Ear Aided Response (REAR) or
Real Ear Aided Gain (REAG) as it only shows the Hearing Aid
Gain andremove the REUR acoustics. TheReal Ear to
CouplerDifference (RECD)is the differencebetween
theoutput of a hearing aid measuredin the ear canal versus
what is measured in a 2-cm3 coupler. The RECD is affected by
individual differences inear canal volume and
tympanicmembrane impedance.
Thecoupler gain typically exceeds the REIG because
oftheRECD effect.CORFIG (Coupler Response for Flat
InsertionGain)is the difference between2cc coupler gain
andREIGandtopredict the amount of REIG, the CORFIG
issubtracted from the 2cc coupler gain.
Real Ear Measurements Probe
2 cc Coupler

25. 250 Hz 500 Hz 1000 Hz 2000 Hz 4000 Hz 8000 Hz
BTE 4 2 0 1 5 -1
ITE 1 2 -1 0 -2 -11
ITC 1 2 -1 0 -5 -13
CIC -7 -7 -9 -7 -18 -23
BL -2 -5 -3 12 4 -11
CORFIG Values for Different Styles of Hearing Aids (Macrae et al., 1996)

26. ➢Selecting the Prescriptive Formula
➢Linear Amplification:constant gain for varying input levels
➢Nonlinear Signal Processing:greater gain for low input levels and less gain forhigh-input
levels
Currently, most hearing aids use nonlinear signalprocessing and hearing aids providing
linearamplification are not as commonly usedas in thepast.For both linear and non-
linearamplification hearing aids, the current most popular prescriptive procedures
includeNAL-NL2 and DSL i/o V5.0
➢National Acoustics LaboratoryNon-Linear 2 (NAL-NL2)
NAL-NL2 is the most recent attempt to provide a tool toassist audiologists in fittinghearing
aids moreaccurately. This procedure is reportedly based on the principle of providing a
frequency-gainresponse that maximizes speech intelligibility, while keeping the overall
loudness of the input signals at a level that is no greater than that perceived by a listener with
normal hearing.
➢DesiredSensation Level Input/Output (DSL i/o V5.0)
This is a comprehensive software-based program designed to help audiologists select and
verifythe performance of linear and nonlinear hearing aids. Theprimary goal of DSL i/o V5.0 is
to place conversationalspeech in the patient’s most comfortable listening range.
Thecomfortable listening range targets are approximately midway between the participant’s
threshold of audibility and thepredicted (or measured) upper limit of comfort (one standard
deviation below Loudness Discomfort Level [LDLs]).

27. THANK YOU