 Pre-selection
factors
Selection
 Prescriptive and comparative procedures
 Functional gain and Insertion gain methods
Verification
 Use of impedance, OAEs and AEPs audiometry
 Hearing aids for conductive hearing loss
 Hearing aids for elderly
 Selection of non-linear programmable and digital
hearings
 The
hearing assessment (used as base for
selection of hearing aids)
 The
selection and fitting
 Verification
 Orientation
 Validation
& counseling
Based on style and placement
 Body level Hearing aids
 Behind-the-ear (BTE) Hearing aids
 In-the-ear (ITE) Hearing Aids
 In-the-canal (ITC) Hearing aids
 Completely in the canal (CIC) Hearing Aids
Based on Hearing aid features
 Volume control
 Telecoil
 Compression:





Peak clipping
Compression limiting
Single channel compression
Multi-channel compression
Wide Dynamic Range Compression (WDRC):




BILL (Bass increases at low level)
TILL (Trill increases at low level)
PILL (Programmable increases at low level)
Noise Reduction Algorithms
 Directional Microphones
 Feedback reduction

1. The Case History
 Case history is the primary and most important in
any assessment.
 A thorough knowledge of the complaint, history, the
nature of problem and their own perception is most
essential to proceed with the correct line of
assessment and management with more chances of
a satisfactory outcome.
2. Pre-fitting Questionnaires
Pre-fitting questionnaires helps us in obtaining
preliminary information which helps us customize
the selection and fitting procedure better
 Audiological
factors
 Non-Audiological
factors
 Type
of hearing loss
 Degree of hearing loss
 Pattern of hearing loss
 Speech recognition/identification ability
 Nature of hearing loss
 Dynamic range
 Conductive



hearing loss
The primary treatment option is medical/surgical
If could not be treated medically, then hearing
aids
Don’t have speech recognition issues and hence,
hearing aids will be sufficient to overcome the
problems related to the hearing loss
 Sensorineural



hearing loss
Hearing aids are the primary treatment option
Most hearing instruments are fitted to this type
The type of hearing aid selected depends on
other audiological factors

Individuals with retro cochlear pathology have
been found to benefit less from a hearing aid.

Other strong contraindications for HA candidacy
are, (severe) tolerance problem to loud sounds and
very poor speech discrimination scores

Mild degree – Hearing aid should be given for
understanding of soft speech

Depends on individual need

If hearing aids are worn, they most likely are not
worn consistently

Individuals with profound hearing loss will benefit
less from the smaller devices (ITE, ITCs, etc) as they
cannot provide sufficient power or amplification.

Profound losses, when acquired late in life, hearing
aids may easily be rejected because they are not able
to restore tonal quality in those cases.

This helps in selection of type of signal
processing and number of channels

Flat pattern-single channel/analog type of
hearing aid

Sloping pattern-different number of channels

Flat and gradually falling/rising pattern-good
candidates

Precipitously sloping-less successful candidates
 Higher
is the speech recognition ability
better is the prospects for good results with
amplification
Nature of hearing loss
 Progressive – Select a hearing aid with more
residual gain and that could be programmed
to increase the gain
 Static
Dynamic range
 UCL-PTA/SRT
 Reduced dynamic range- select a hearing aid
circuit that has varying degrees and types of
compression
 Age
 Listening
Environment
 Communication needs
 Physical Attributes
 Cosmetic concerns
 Financial issues
 Otological examination
 Aging
is one of the most common causes of
hearing loss.
 It
indirectly effects several factors like the
hearing needs, expectation from the hearing
aids, maximum output level, ease of
manipulation, etc.
 The
class, design, size, technology and cost
of hearing aid selected based on the age

Needs from the hearing aid vary majorly based on the
listening environment.

In quiet conditions like the hearing aid testing room,
or a library or in the house, the amplification
required is less,

In noisy areas like a factory, in the traffic, at a party
etc, the amplification needs are greater.



Requirement of greater amplification
Requirement of additional noise reduction algorithms in
their device.
Switching between quiet and noisy listening situations flexible technology.

People vary widely in the amount of interpersonal
communication

People who live alone or work in jobs that require little
verbal communication would have less expectation from
the hearing aid

People who live with a number people and/or spend many
hours in meetings, classes, or discussions, demanding more
communication skills would want better ability to hear and
understand

Infants and young children need to hear more of the
acoustic cues of speech to recognize what is being said
than do adults.

For children who have hearing loss, it is particularly
important to amplify speech and other environment sounds
so that they are comfortably loud. This is necessary in
normal speech and language development


Structure of the outer ear (the pinna and the ear canal)

The shape and size of the outer ear determines the type of
hearing aid

Congenital Artesia or a malformed pinna will indicate the need
to select a bone conduction hearing aid

A narrow ear canal will restrict the use of small ITEs or ITCs.
Manual dexterity

Problem mainly in small children and the elderly.

Additionally individuals with cerebral palsy, autism, or any
other neuro-motor disorders may find it difficult to manipulate
hearing aid controls or to put and remove the ear mold.

A body level HA will make it easy to manipulate the hearing
aid controls but insertion and removal of the ear mold still
remains a problem.
 As
far as possible a suitable small device that
can meet the listening needs of the
individuals should be prescribed.
 Greater
degrees of loss requiring larger
gains, or individuals not suitable to use small
aids due to physical limitations

Almost all individuals want to have a hearing aid
which meets their needs sufficiently within a
reasonable price range.

The initial cost, the cost of batteries and other
accessories, the cost of repairs and the expected
lifespan of the aid are important considerations
for anyone who is buying a hearing aid.

Hearing wearers would want an aid that will
need few repairs, have a long warranty as well
as life span, and will meet their needs for the
lowest cost

Otologic examination prior to the fitting procedure is
mandatory.

There are several medical conditions which contraindicate the use of a hearing aid, like presence of any
infection or active discharge in the outer or middle
ear, etc.

In some cases there could be an associated condition
that may require immediate medical attention rather
than hearing aid fitment.

Sometimes the condition leading to the hearing loss
can be reversible or may be overlapping an
irreversible condition.

In both the cases, alleviation of the reversible
condition is the primary goal.
 Hearing
assessment (used as base for
selection of hearing aids)
 Selection
 Verification
 Orientation
 Validation
& counseling
 Pre-selected
hearing aids’ gain and other
characteristics
 Provide optimum frequency-gain and output
characteristics
 Two methods


Prescriptive
Comparative
 Indirect
approach
 Amplification is prescribed using a formula that
links some characteristics of a person to the
target amplification characteristics
 Some
characteristics of hearing impaired
individuals is measured and required
amplification characteristics are calculated.
 These
required amplification characteristics are
called amplification targets
 Formula
can be based on the thresholds or
supra threshold measures and the situations
in which the hearing aid are to be worn.

Linear hearing aid
 Threshold based procedures
 supra threshold based procedures

Nonlinear hearing aid
 Threshold based procedures
 supra threshold based procedures
1) Inverted audiogram method (Mirroring of audiogram)

Kundsen and Jones (1935)

Here the frequency response of the hearing aid (HA)
is set to mirror the amount hearing loss across
frequencies

Every 1 dB increase in hearing loss requires 1 dB of
additional gain to compensate.

The gain provided at each frequency is equal to the
loss in dB at that frequency

Drawback: In case of sensorineural hearing loss,
mirroring may lead to excessive gain leading to over
amplification

Introduced by Lybarger for the Radio Ear Hearing Aid Company
in 1944

The gain of the aid at any frequency was estimated to be one
half of the hearing threshold at that particular frequency.

Gain = A/2 + (A-B)/4
Where: A= Average air conduction threshold (.5, 1 and 2 kHz)
B= Average bone conduction threshold (.5, 1 and 2
kHz)
(A-B)/4 = Correction factor for an air-bone gap




For maximum gain, a 15 dB reserve is added to the gain, and
a -10 dB correction was recommended for a binaural fit.

This rule has been serving as the basis for almost all pure tone
thresholds based fitting formulae and for most MCL based
procedures
 Drawback:
The acoustic spectrum of speech: Low
frequencies are more intense and the high
frequencies are less intense
Amplification should not be equal at all the
frequencies












Berger et al (1997)
Frequency specific gain was given
500 Hz – 0.5 HTL
1KHz – 0.63 HTL
2 KHz – 0.66 HTL
3 KHz – 0.59 HTL
4 KHz - 0.5 HTL
6 KHz - 0.5 HTL
Gain given at 500 Hz, 4 kHz and 6 kHz was ½ of the hearing
threshold
For frequencies between 1K-3K –gain given was slightly more
than ½
This based on the assumption that mid frequencies are more
important for speech.
Addition gain for conductive hearing loss - ABG*0.2 was given
for CDHL
Prescription of gain and output
 Based on half gain rule with an addition of low
cut
 Mc. Candless and Lyregaard (1983)
 250 Hz - 0.5 HTL -10
 500 Hz – 0.5 HTL - 5
 1KHz – 0.5 HTL
 2 KHz – 0.5 HTL
 3 KHz – 0.5 HTL
 4 KHz - 0.5 HTL


Output = UCL500 + UCL1k+ UCL2k
3

Prescribes same gain as POGO for losses less than
65 dB HL.

For greater losses, gain increases by 1 dB for
every 1 dB increase in hearing loss.
125 Hz - 0.5 HTL -15 + x
 250 Hz - 0.5 HTL -10 + x
 500 Hz – 0.5 HTL – 5 + x
 750 Hz - 0.5 HTL – 2 + x
 1KHz – 0.5 HTL + x
 2 KHz – 0.5 HTL + x
 3 KHz – 0.5 HTL + x
 4 KHz - 0.5 HTL + x
 6 and 8

 X-correction
factor
 X = 0, if AC thresholds are lesser than 65
dBHL
 X=0.5(AC – 65 dB)
 POGO
II is useful for individuals up to
profound hearing loss
 Output
prescription is same as POGO
 National
 Makes
Acoustic Laboratories of Australia
use of loudness equalization
 If
one frequency dominates the overall
loudness, the patient will turn down the
volume to make the sound comfortable. This
will reduce loudness of all other frequency
regions. This may reduce the intelligibility.
 Given
by Byrne and Tonnison (1976)
 The
NAL formula for selecting the gain and
frequency response of a hearing aid
 Makes use of equal loudness curve and shape
of the spectrum into consideration
 This
is very similar to POGO formula
 However,
it was observed that it did not
provide loudness equalization
 NAL
was modified
 Calculation
of required real-ear gain using
the NAL-R formula (Byrne and Dillon 1986).
 Frequency-gain
response that gave equal
loudness needed to vary at 0.31 times the
shape of the audiogram
 The
profound correction factor (Byrne et al
1991).
 For
conductive hearing loss, 1/4th of ABG is
added

1986
Assumption that the gain in mild to moderate hearing
losses more closely approximate 1/3rd gain rule as a
target insertion gain

Losses greater than moderate -two third gain rule.

Corrections were applied to lower frequencies to
prevent excessive amplification and to eliminate the
possible upward spread of masking.
Frequency (Hz)
Insertion gain
500
1/3 HTL – 5
1000
1/3 HTL - 3
2000
1/3 HTL
3000
1/3 HTL
4000
1/3 HTL








The Desired Sensation Level (DSL) approach was developed
originally with preverbal children (Seewald& Ross, 1988,
Seewald et al.1985).

It tries to make speech comfortably loud at each frequency
region rather than equally loud

The goal is to select hearing aid frequency/gain
characteristics that place as much as possible of the long
term speech spectrum into the amplified range.

Hearing thresholds are measured via insert earphones in
SPL, and compared with the long term speech spectrum
information stored in the computer database.

The computer software calculates the amount of gain
required to place the speech spectrum at the desired
sensation levels for amplified speech.
 The
sensation level targets for bands of speech
are placed one standard deviation below the
estimated MCLs for pure tones.
 Because
these measurements define the
differences between the real ear and coupler
(that is RECD), electroacoustic response shaping
can be performed in the hearing aid test box
with accurate predictions of how the hearing aid
will perform on the individual.
Equal Loudness Procedure
Watson and Knudsen,1940


This procedure was designed to amplify speech to MCL.
MCL at 1 kHz as reference

Present tones at other frequencies and vary the level and find the
loudness same as that of MCL at 1 kHz

This level minus 20 is the gain

Gain is plotted as a mirror image of an equal loudness contour.
Loudness matching across octave frequencies from 125 to 8000 Hz.

Not clear as why a 20 dB difference exists between the MCL and
the recommended gain.
Wallenfels Bisection Approach (Wallenfels,
1967)

Obtain in pure-tone audiogram and plot in SPL

Obtain UCL and plot in SPL

Optimum hearing level (= MCL) is assumed to be
the center point between threshold of hearing and
UCL 1 kHz and 4 kHz

Gain is obtained by subtracting 65 dB from
optimum hearing level
 Shapiro
 Obtain
MCL approach (1975, 1976)
pure tone threshold
 Measure MCLs and UCLs for pulsed narrow
band noise at 500, 1000, 2000, 3000, and
4000 Hz.
 MCL defined as the level 5 dB below the
lowest intensity level described as being too
loud two of three times.
 The desired use gain for each frequency was
calculated by subtracting 60 dB from MCLs at
each frequency, except at 500 Hz where gain
is to be 10 dB less than 1000 Hz and at 250, 15 dB
 A constant 10 dB is added to the final gain
calculation for reserve.
CID
 Skinner,
Pascoe, Miller, and Popelka (1982)
 MCL
(Lower range and upper range) and LDL(UCL)
for pulsed pure tones at 250 Hz – 6000 Hz.
 Find
out midpoint between threshold and the
midpoint of MCL range.
 Gain
 250 Hz and 6000 Hz is mid point between threshold and



the midpoint of MCL range
500 Hz to MCL
1 kHz and 2 kHz to 90% of the range between threshold and
the midpoint of MCL range
2 and 4 kHz to 80%
 Preferred
listening level is at the mid point
of the range between upper limit of
comfortable loudness and threshold. This PLL
is the aided speech spectrum
 MPO=
UCL + 12
 Selecting
Hearing aids for patients
effectively, Humes (1988)
 It
is a software program
 Cox
and Pascoe’s to prescribe MPO and NAL-R
for gain
Underlying theory behind most prescriptive
strategies can be described as loudness
normalization (LN) rationale or loudness
equalization (LE) rationale.
 Loudness normalization (LN):
 the overall goal is to restore normal loudness
perception for the hearing aid user.
 For example the speech presentation levels
judged to be "soft" “comfortable”, and "loud" by
normal hearing individuals also should be judged
"soft," "comfortable," and "loud" by the hearing
aid wearer.

Prescriptive methods for
non-linear hearing aids
Loudness based
measures
Threshold based
measures
LGOB
IHAFF
VIOLA
Scal Adapt
NALNL1
Fig6
DSL(i/o)
 McKillion,
(1995)
 Fitting of non-linear hearing aids that have
wide dynamic range compression
 More specifically for hearing aids which use
Killion amplifier.
 SN
HL patients required less gain for intense
sounds and more gain for soft sounds and
also for the reason that it is used for nonlinear hearing aids.

For 40dB SPL input levels:
IG = 0
for HL between 0 to 20 dB HL
IG = AC thr - 20 for HL between 20 to 60 dB HL
IG = AC thr - 20 - 0.5 (AC thr-20) for HL > 60 dB HL

For 65 dB SPL input levels:
IG = 0
for HL between 0 to 20 dB HL
IG = 0.6 (AC thr -20) for HL between 20 to 60 dB HL
IG = 0.8 (AC thr -20)
for HL > 60

For 95 dB SPL input levels:
IG = 0
for HL< 40 dB HL
IG = 0.1 (AC thr - 40)
for HL > 40 dB HL
(Dillon, 1999; Byrne et al, 2001)
 Extension of the NAL-R fitting strategy for
linear amplification (Byrne et al., 2001)
 NAL-NL1
was designed for nonlinear signal
processing and provides different
prescriptive targets as a function of input
level (50, 65 and 80 dB SPL)
 Loudness
Equalization rationale
The aim is Maximizing Speech Intelligibility:
.
 For lower input level, - greatest weight to mid
frequencies

Lesser gain at frequencies of greater hearing loss
(There may be dead region in those frequencies) –

Speech Level

The aim of NAL-NL1 is to maximize speech
intelligibility for any input level of speech above
the compression threshold, while keeping the
overall loudness of speech at or below normal
overall loudness. The formula is derived from
optimizing the gain-frequency response for
speech presented at 11 different input levels to
52 different audiogram configurations on the
basis of two theoretical formulas. The two
formulas consisted of a modified version of the
speech intelligibility index calculation and a
loudness model by Moore and Glasberg (1997).


. Desired Loudness
Another rationale behind the optimization procedure used to derive NAL-NL1 is to ensure that the
overall loudness of speech does not exceed normal overall loudness.














The only information required by both of these models is hearing threshold, and the speech
spectrum levels input to the ear after amplification.
The unique aspect of NAL-NL is that the impact of high levels and degree of hearing loss with
regard to speech recognition is taken into account. (as the SII formula accounts for Speech level
distortion and Hearing Loss Desensitization)
It is based on a complex equation that specifies insertion gain at each standard 1/3-octave
frequency from 125Hz to 8000 Hz.
At each frequency the gain depends on,
Threshold at that frequency,
Three-frequency average threshold,
Slope of the audiogram from 500 – 4000Hz, and the
Overall level of a broad band signal with a
Long term spectrum like that of speech.
The NAL-Non-linear software program displays the result as either gain curves at different levels,
or I-O curves at different frequencies.
These curves can be for a 2 cc coupler, an ear simulator, or the real ear. In case of a real-ear
prescription, the gains can be either insertion gain or REAG.
For multi channel Hearing aids, the software also recommends cross over frequencies,
compression threshold, compression ratios and gain for 50, 65 and 80 dB SPL input levels.











NAL-NL2
NAL-NL2 is the second generation of prescription procedures from The National Acoustic
Laboratories (NAL) for fitting wide dynamic range compression (WDRC) instruments.
Like its predecessor NAL-NL1 (Dillon, 1999), NAL-NL2 aims at making speech intelligible and
overall loudness comfortable.
This aim is mainly driven by the fact that less information is available about how to adjust gain to
optimise other parameters that affect prescription such as localisation, tonal quality, detection of
environmental sounds, and naturalness.
In both formulas, the objective is achieved by combining a speech intelligibility model and a
loudness model in an adaptive computer-controlled optimisation process.
Adjustments have further been made to the theoretical component of NAL-NL2 that are directed
by empirical data collected during the past decade with NAL-NL1
In comparison to NAL-NL1, NAL-NL2 prescribes a different gain-frequency response shape, and
slightly higher compression ratios are prescribed for those with mild or moderate hearing loss.
NAL-NL2 further takes the profile of the hearing aid user (age, gender, and experience), language,
and compressor speed into consideration.
As a result of the new modifications made to the standard SII formula, NAL-NL2 prescribes a
different gain-frequency response shape than NAL-NL1. Specifically, relative to the NAL-NL1
prescription, NAL-NL2 prescribes relatively more gain at the low and high frequencies than at the
mid frequencies, see Figure 4.











Desired Sensation Level – DSL(i/o):
Coenelisse, Seewald& Jamieson, 1994
This procedure is a modification of DSL which can be used with adults and children.
A software implementation of the desired sensation level (DSL[i/o]) is called as DSL v4.1 (
Seewald et al, 1997)
The DSL I/O uses not only the information that is commonly available (threshold data) when
hearing aids are selected but additional measurements like loudness Discomfort Levels (LDL),
RECD are also used.
The goal of the DSL [I/O] hearing aid fitting procedure is to prescribe amplification
characteristics such that the entire range of acoustic signals available to a patient with normal
hearing is placed within the dynamic range of the patient with hearing loss (Cornelisse et al,
1995).
The underlying rationale, with regard to relative loudness across frequency bands, varies
according to the parameters chosen.
When the non-linear variable compression ratio mode (CR changes as a function of input level) is
chosen, the targets generated are based on an LN rationale.
When linear compression ratio mode is chosen (CR remains constant above the CT), the targets
generated are based on an LE rationale (Seewald et al. 1997).
When it is used to predict performance for a wide dynamic range compression aid, the DSL (i/o)
selects compression characteristics relative to the user’s perceived growth of loudness. At low I/P
level (soft speech), more gain is applied to the input signal than recommended for a linear gain
device and at high input level (loud speech) less gain is recommended than for a linear gain
device.
The difference between DSL (i/o) and DSL formulae is that the DSL (i/o) produces several inputlevel-dependent targets, whereas more conventional approach provide a single target only
regardless of the i/p signal level.
 Loudness
normalization: the main goal is
to restore the loudness of typical speech
input levels to those that are
experienced by normal hearing
individuals.
 That
is, moderate sounds should be heard as
moderate

Pluvinage & Benson, 1988, Pluvinage, 1989)

LGOB is the first clinically practical procedure to
accomplish loudness normalization
Stimuli: Three bursts of half-octave bands of
noise separated by half second intervals of
silence are presented at random frequencies and
at levels between threshold and discomfort.
 The test is performed at the octave frequencies
from 250 to 4 kHz.


The patient is asked to make loudness judgment based on
the following categories

cannot hear – CH,
very soft-VS,
soft-S,
comfortable-C,
Loud-L,
very loud-VL
Too loud – TL







The average levels corresponding to each loudness
category are then compared to the loudness needed to
produce the same categories in normal hearing people.

For each input level, the gain needed to normalize
loudness is deduced.
(Valante and Van Vliet, 1997; Cox and Flamme, 1988).
 VIOLA employs a loudness normalization rationale,

Loudness rating data are obtained using the Contour
test (Cox et al, 1997)

Pulsed warble tones are presented in an ascending
sequence from 5 dB above threshold until the patient
indicates that it is uncomfortable

An ascending approach is employed, typically
between 500 and 3000 Hz.

At each level, patient indicate which of the following
7 categories best describes the loudness:

7
6
5
4
3
2
1







= uncomfortably loud
= loud, but OK
= comfortable, but slightly loud
= comfortable
= comfortable, but slightly soft
= soft
= very soft
The results of three or four ascending sequences are
averaged.
Independent Hearing aid Fitting Forum used loudness
scaling to normalize loudness at each frequency.
 Makes use of VIOLA (visual input / output Locator
Algorithm) and Contour test.


In the IHAFF/ contour protocol, the VIOLA software
program presents the result of the loudness
normalization as 3 points on an input-output function
at each frequency at which loudness scaling is carried
out.

These 3 points show the output level needed to
normalize the loudness of 1/3 octave bands of speech

Keissling, Schubert & Archut (1996)
For the usual loudness normalization procedures hearing
aid prescription is a three step process

The loudness scale for the patient is measured

At each level, the gain needed to normalize loudness is
calculated

The hearing aid is adjusted to match the target gain.

Scal Adapt is a clever one step combination of these
three steps.


The aid is pre-adjusted using an established
threshold based procedure.

Loudness scaling using an 11 point scale is then
performed while the patient is wearing the hearing
aid.

Instead of finding the loudness that corresponds to
each input level, only some input levels are
presented and the clinician adaptively adjusts some
characteristic of the hearing aid until the patient
rates the loudness that would be perceived by a
normal hearing person listening unaided.

For example, if a normal hearing person would rate a
sound of 60db SPL at a particular frequency as
comfortable, then the gain of the hearing aid is
adjusted until the hearing impaired person also rates
60 dB SPL sound at that frequency as comfortable.

PAL (Palmer, Mueller, & Moriarty, 1999)

12 sounds, for example, water boiling, door
slamming, electric razor etc
Present it - 4 sounds soft, 4 sounds moderate,
and 4 sounds at loud levels and the person to
rate
 use that same kind of contour rating scale from
very soft to uncomfortably loud


This also includes satisfaction rating
 is
a tool used to predict the amount of
speech that is audible to a subject with a
specific hearing loss
 First given by French and Steinberg (1947)
 Method Ao (4)
 Method Ao (6)
 Method As
 Count the dot method
Method Ao (4)
 Threshold
at 500, 1k, 2k and 4k are
considered.
 The shaded are represents the speech
dynamic range.
 The
shaded area exceeding the threshold
(down from the threshold on the audiogram)
represents the audible speech in the unaided
condition.
 Similarly
the shaded area exceeding the
shifted thresholds represents the audible
speech in the aided condition.
 The
audible dB at each of the 4 frequencies
are added up and the sum is divided by 120.
 Example:
 Unaided
condition,
 If audibility at,
500 Hz – 30 dB;
1kHz – 25 dB;
2kHz and 4kHz – 0 dB
 AI = 30 + 25+ 0+ 0 = 0.46
120
 Aided
condition, HL = 500 = 20, 1 k = 25, 2k
= 30, 4k = 35
 500 Hz – 30 dB;
 1kHz – 25 dB;
 2kHz – 20
 4kHz – 15 dB
AI = 30 + 25+ 20+ 15 = 0.75
120
 Method
Ao (6):
 This method includes the data measured at
3kHz and 6kHz
Consists of 4 steps:
 The sum of audible decibels - (S1) are
obtained at 500 Hz, 1 kHz and 2 kHz.
 The sum of audible decibels - (S2) are
obtained at 3 kHz, 4 kHz and 6 kHz.
 Ao (6) is obtained by dividing the total by 120.
AI = S1 + S2/3
120
Method As:
 This method approximates Ao (4) (here‘s’
represents ‘simple’)
 This method is considered to be somewhat
less accurate than Ao (4)
 With the 25 dB dynamic range, the division
by 120 from Ao (4) becomes simply a division
by 100.
 “Count
the Dot method”
 Mueller and Killion, 1990
 This procedure incorporates 100 dots
 The method meets the criteria of weighting
different frequencies according to their
importance for understanding speech and
these dots are fit into the speech spectrum
on an audiogram format.
 AI
is renamed as Speech Intelligibility Index
and ANSI 1997 standards give procedure for
calculation of SII.
 Thresholds
 Number
of audible dBs
 Multiply the Number of audible dBs and
frequency importance function (Bandimportance function)
 Average for all the frequencies = SII
 This
is a direct method in which client’s
performance is assessed.
 Classic
method given by Carhart (1946).
 Ranking
of hearing aids based on word
recognition performance when comparing
variety of preselected hearing aids
1. Obtain SRT, SIS & UCL in sound field in
unaided condition. SIS is done at 25 dB SL
reference SRT
2. Hearing aid is put on. The gain is adjusted
such that a 40 dB HL speech is at
comfortable level. In this volume control
position, aided SRT and UCL are measured
3. HA is kept at FOG and SRT and UCL are
measured
4. HA gain is adjusted such that a 50 dB HL speech
is at most comfortable level. In this volume
control position, speech performance is
measured under 2 SNR conditions, that is, one
with WBN and other with Saw tooth noise
5. The intensity of noise is increased or decreased
till the subject could repeat 50% of the word
presented, The difference between speech and
noise is the SNR 50.
6. The gain is adjusted such that a 40 dB HL speech
is at comfortable level. In this volume control
position, MCL, aided SRT and UCL are measured
in order to check the reliability of the step 2
 Carhart
procedure is considered too
subjective, too time consuming and is rarely
used.
 Modification
of the procedure
 Measurement
 Jerger
is not done at FOG setting
(1976) suggested using SSI in
competing message at different MCRs of + 20
to -20 dB
 This
approach is identifiable with master
hearing aid evaluation units.
 Specific electro acoustic features of hearing
aids are produced from settings of a master
hearing aid, and the final selection is made
from a comparison of the settings using
speech materials.
 The second or the prescriptive, step is to
specify the set of optimum electroacoustic
characteristics that are to be integrated in
the patient’s aid, duplicating the master
hearing aid settings (McCandless,1995)
 Selecting
prescriptive formula
 Selecting hearing aid features (Vol.
DAI/telecoil Directional mic etc)
 Selecting signal processing schemes
 Selecting hearing aid style
 To
help meet listening needs (Speech
understanding)
 For localization
 For maximum use of residual hearing
 Should a give a good quality output
 Hearing aid should provide amplification in
the comfortable range
 Process
by which we see whether the
selected device is meeting the target or
goals. There few methods
 1)
Functional gain measurement
 2) Insertion gain measurement

Is an objective comparison between the
unamplified versus the amplified sound that
“reaches the ear”. Such comparisons are called
Rear-ear Insertion gain (REIG) measurements or
Insertion gain measurements

REM (Real ear measurements) is used a synonym
used for Insertion gain measurements

First study in the form of probe microphone
measurement was made by Weiner & Ross (1946)






All REM systems are comprised of the following:
a sound field speaker,
a reference microphone,
a probe-tube microphone and
a computerized micro processing unit.
Sound Generated

REM system generates its own calibrated sound source. The loudspeaker
delivers the test signal generated by the system to the sound field.

The reference (Control) microphone is responsible for calibrating the
sound field and can be positioned just below or above the ear. The REM
system uses the recordings done by reference mic to adjust the signal
source to achieve specified values.
Used to regulate the sound level near the ear to the required level.


The probe tube microphone is the main
measurement microphone
 a very soft and slim silicone rubber tube, one
end of which is inserted into the ear canal; and
the other end is connected outside the ear to
small microphone housing
 Earlier small metal tubes were used
 Later A small electret mic itself was placed in
the ear canal (called as Harford-Preves
technique).

 Stimulus
type
 Test Environment
 Signal Level
 Distance
 Azimuth
 Probe tube insertion depth
 Head Restraint







Varieties of stimulus are available on most real ear
probe mic system. Such as pure tones, warble tones,
clicks, NBN etc.
Pure tone: Continuous sinusoid of a single frequency.
But because of standing wave from reflective
surfaces. Pure tone stimuli are not recommended
Warble tones: FM of a single frequency of a pure
tone. Not influenced by standing wave.
NBN: Produced by 1/3rd octave band filtering of
white noise. It can be used as swept frequency or
single frequency measurement.
Clicks: It is broad band transient signal characterized
by instantaneous onset.
Clicks are difficult to calibrate precisely because of
the inability to limit or define the spectrum.
In addition rapid onset of click may activate the
automatic gain suppression circuit of the hearing aids
thereby giving enormous results
Composite noise: It is composed of large number
of individual sinusoidal signals summed for
simultaneous presentation. The result is “noise
like” stimulus with controlled spectral
characteristics.
 These signals are speech weighted that is high
frequencies having less energy than at the lower
frequencies. The most common speech weighting
is defined by ANSI S3.42-1992. Higher
frequencies continue to decrease in amplitude at
a rate of 6dB/octave. Another speech weighting
is defined ICRA (The international Collegium of
Rehabilitative Audiology (1997)) It rolls off the
high frequencies more quickly than ANSI, at a
rate of 9 dB per octave.


 Interrupted
composite noise. The pauses
are similar to that of natural speech
 There are two Digital Speech signals
available
Digital Speech ICRA (DIGSP ICRA) and Digital
Speech ANSI (DIGSP ANSI)
 International
Speech Test Signal (ISTS)
 This signal includes natural sentences of six
languages spoken by a female. The ISTS was
developed by a group within EHIMA
(European Hearing Instrument Manufacturers
Association).
 This is more speech-like than the other
existing test stimuli.
 The signal reflects a female speaker
incorporating and combining six different
mother tongues (American English, Arabic,
Chinese, French, German, and Spanish).
 Envt.
can affect the validity of the results.
 It is suggested to measure the ambient
levels in the proposed test room prior to
initiating IG measures to avoid contamination
 It is advisable to compare IG results obtained
for several subjects in the proposed test
room with those obtained in a sound treated
room.
 Test
level should be high enough to avoid
contamination by ambient noise level
 Test level should not be so great as to send
the hearing aid into saturation or to activate
its compressor circuitry
 Should not cause discomfort
 Level of 60 to 70 dB SPL is suggested
 For
a non linear hearing aid testing is done at
multiple levels usually 55, 65 and 80 dB SPL

Testing at closer distances of loud speaker creates the risk of
entering into the near field. When this occurs, small changes in
the distance leads to large measurement errors. It also creates
discomfort to patients.

Keeping the loud speaker too far results in interference of
ambient noise and reverberation

Jecca (1987) compared two distances, 1m and 1.5 m in two
environments, in an audiometric test room and a non-standard
consultation room. There was no difference between the two
situations and two distances.

Studies have shown that a distance of 20 cm it was unpleasant
for the patient and distance of 1 m was far more comfortable for
the patient.
Most manufacturers recommend the distance between 0.5 and
1.0 meter.


As was noted earlier, audiologists should review the
documentation provided with their specific real-ear system to
determine the recommended protocols with their equipment. As
an example, Audioscan recommends placing the patient directly
in front of and facing the speaker (0 degrees azimuth) at a
distance of 0.45 m to 0.6 m.
Fonix recommends 12 inches, 45 degrees azimuth

Killion and Revit (1987) – Reported that reduced variability of
repeated measures is obtained then the loud speaker is placed 45
degrees to the sid of 45 degrees elevation
This reduced the average test retest deviations upto 1 dB relative
to 0 degree azimuth
90 degree azimuth has better test retest variability than 0 degree
azimuth. However, this orientation may interact with directional
mic, HSE



Mueller (1992) reported 90 degree results in significant error and
should be avoided



It’s a source of greatest variability in RE measures.
Insertion depth should not be so much that it touches
TM
Place the tip of the probe tube within approximately
5 mm of the eardrum to avoid standing waves and to
assure that the high frequency components of the
response are accurately measured. As Dirks and
Kincaid (1987) illustrated, the closer the probe tube
is placed to the eardrum, the more accurate high
frequency measurements become. For clinical
purposes, a placement within 5 mm of the eardrum is
appropriate as it will provide accuracy within
approximately 2 dB of the true value at the eardrum
up to 8 kHz.
 Killion
and Revit (1987) demonstrated that
the variability associated with different LS
azimuth is due to small head movements.
Head restraint should be expected to reduce
the likelihood of error but its difficult to use
head restraint clinically
 Care should be taken
A. Probe Tube Calibration
Probe tube calibration accounts for the acoustic effects the probe tube
introduces as sound travels through it.
In effect, calibration removes the acoustic effects the probe tube during
real-ear measurement.
One has to compare the output form the reference mic to the
simultaneously recorded response of the signal travelling thorugh the
probe tube attached to the test mic.
The difference between these two responses reflect the effect of probe
tube.
In most equipments, the acoustical transmission effects of probe tube are
stored and hence the response from two mic should be same.

B. Otoscopic Examination
Prior to conducting any real-ear measurement, it is
important to perform an otoscopic examination. This
serves to provide information about the presence of
cerumen or other debris which may interfere with
placement of the probe tube and/or block the probe
tube.

If the ear canal appears occluded or if cerumen is
located where it may affect probe tube placement,
the cerumen should be removed prior to conducting
real-ear measurements.

Otoscopic examination also provides details regarding
the specific anatomy of the ear canal, which is useful
when placing the probe tube.

C. Location of speaker



One method (visually-assisted positioning) involves
inserting the probe tube a constant insertion depth beyond
the tragus or inter-tragal notch. The guidelines regarding
how far to insert the probe tube can vary, depending on
the age and gender of the patient.
General guidelines suggest: For adult females, insert the
probe tube 28 mm past the inter-tragal notch. For adult
males, insert the probe tube 30-31 mm past the intertragal notch.
For children, insert the probe tube 20-25 mm past the
inter-tragal notch. Certainly normal anatomic variants will
prohibit the placement of the probe tube to these depths
in some patients, while in other patients these locations
may not be deep enough.
'geometrical positioning.‘
 the ridge of the ear mold or hearing instrument
corresponding to the location of the inter tragal
notch is identified.
 Lay the probe tube along the ridge identified above
with the open end of the probe tube extending 5
mm beyond the tip of the ear mold or hearing
instrument.
 Mark the probe tube at the outer edge of the ear
mold or at the faceplate of the hearing aid and
then insert the probe tube into the ear canal until
the mark lies at the rim of the inter tragal notch.






Probe tube placement can also be assisted via acoustical
positioning procedures (ANSI, 1997; ISO 12124:2001). A
simplified method is through visualization and repositioning
based on the REUG curve, monitoring particularly the frequency
region above 4000 Hz.
a. Insert the probe tube less than half way into the ear canal
while presenting a 65 dB pink noise signal or composite signal.
b. A notch in the gain curve above 4000 Hz is likely to be
observed.
c. Gently insert the probe tube deeper while keeping an eye on
the notch which is moving towards higher frequencies.
d. The probe tube is located correctly as soon as the notch is no
longer dragging the gain curve down (-5 dB) in the highfrequencies.
e. Once the measurement is stabilized move the probe tube
marker into position or to attach the probe tube to the probe
tube support.
It is the process of controlling the acoustic
signal at a specific point in space so that the
amplitude remains at the desired level across
frequencies.
 There have been 2 commonly used methods
of sound field equalization
 a. Substitution method
 b. Modified pressure method (this term was
recently recommended by ANSI) / earlier it
was called as modified comparison method
(Preves, 1987; Preves and Sullivan, 1987).

a. Substitution method
 The exact position in the room where the person
will be seated is identified
 without the patient in the room, a mic is placed
at the location the person will occupy for
measurements.
 A signal is produced by the loud speaker,
measured by the mic and deviation from a flat
free field is calculated.
 After that the unoccluded ear testing will be
conducted with the patient in the exact position
.The centre of the patient’s head is placed in
the precise location previously occupied by
microphone
 microphone is located in the ear canal.
 Then aided measurement conducted in the
similar manner as unaided testing. It is usually
done in off line.

b. Modified pressure method
 There are two mics, one that measures SPL in
the ear canal and one that is located some place
in the head and regulates the SPL being
generated by the loud speaker and maintain the
signal at a constant level. There are two major
differences between substitution method and
this. First, there is no equalization conducted
with the patient absent. Second, a second
regulating mic will be present for all the
measurement. It can be done either in online
/offline.


 Feed
in thresholds
 Select prescriptive formula
 Select ear
 Stimuli
 Level
1. REUR (real ear unaided response)
 SPL, as a function of frequency, at a
specified measurement point in the
unoccluded ear canal for a specified sound
field. This can expressed either in absolute
SPL (Response) or again in decibels relative
to the stimulus level (Gain).







They reflect the resonance characteristics of ear canal,
concha, and also the head and torso.
The average adult REUR has a primary peak around 2700
Hz of about 17 dB, and a secondary peaks around 4000 Hz
to 5000 Hz region of 12 – 14 dB. It is the gain provided by
the pinna and the ear canal with consequent head
diffraction effects as measured in the ear canal.
Procedure:
1. Conduct otoscopic examination.
2. Place probe tube in the ear canal, with end of tube at
appropriate distance from the inter tragal notch (e.g.,
within 5 mm of the eardrum).
3. Place patient at appropriate distance/azimuth from the
loudspeaker.
4. Select desired input level.
5. Conduct the measurement.
 Reference
value for the calculation of
insertion gain.
 Also reflects the abnormalities of ear canal
or the middle ear.
2. REAR (Real-Ear Aided Response)
 SPL, as a function of frequency, between the
SPL at a specified measurement point in the
ear canal for a specified sound field, with
the hearing aid (and its acoustic coupling) in
place and turned on.









The gain of the hearing instrument across
frequencies, measured in the ear canal. It is a direct
measurement how a hearing aid will perform in a real
ear.
Procedure:
1. Conduct otoscopic examination.
2. Seat the patient at the appropriate
distance/azimuth from the loudspeaker.
3. Place probe tube in the ear canal, with end of
tube at appropriate distance from the inter tragal
notch (e.g., within 5 mm of the eardrum). NOTE: if
the REAR/REAG is being used to calculate insertion
gain, be sure to position the probe tube at the same
location as the REUR/REUG measurement.
4. Insert the hearing instrument into the client's ear
while holding the probe tube so that its position in
the ear canal is not disturbed.
5. Turn the hearing instrument on and set the user
gain control to the desired setting.
6. Select desired input level.
7. Conduct the measurement.
 Clinical
applications .
 Serves as a reference for insertion gain
calculation
 To find out inter modulation distortions in
the hearing aid
 Trouble shooting the hearing aids
 Helps in finding out the maximum output in
the real ear of the hearing aid when it is in
saturation.
3. REIG (Real-Ear Insertion Gain)
 The real ear insertion response (REIR)(ANSI
S3.46-1997): Difference in decibels, as a function
of frequency, between the REAR and the REUR,
obtained with the same measurement point in
the same sound field conditions.
 The REIG is the value, in decibels of the REIR at
a specific frequency. The amount of gain
provided by the hearing instrument alone
calculated by subtracting the REUG from the
REAG across frequencies or by subtracting the
REUR from the REAR across frequencies.
 REIG = REAG – REUG






Procedure :
Step 1: Conduct an REUR
Step 2 : Conduct an REAR, using the same sound field
conditions and measurement point as the REUR (i.e.,
probe tube placement and signal level).
Step 3: Subtract the REUR from the REAR across
frequencies or subtract the REUG from the REAG
across frequencies.
Step 4: Adjust hearing instrument characteristics so
that the REAR (REAG) and thus the subsequent
calculation of REIG provides the best match to the
target REIG values across frequencies.



REOR (Real ear occluded response)
SPL as a function of frequency, at a specified measurement
point in the ear canal for a specified sound field, with the
hearing aid (and its acoustic coupling) in place and turned
off. This can be expressed either in SPL or as gain in
decibels relative to the stimulus level.
Here the effect of placement of ear mould or hearing aid
in the ear easily can be measured. For open ear fitting
REOR may be very similar to REUR at some frequency
region. For most of the ear mould styles REOR will be
substantially below than REUR. In cases of venting REOR
comes higher than that of REUR at the region around 1500
Hz, because of the resonance. REOR helps in the
estimation of insertion loss. Tight fitting hearing aid the
REOR falls below the input level. So it becomes very
important in the measurement of REIR.











Procedure:
REUR measurement (even if it is not necessary)
Hearing aid will be placed. Make sure the hearing aid is
turned off.
Place probe tube in the ear canal, with end of tube at
appropriate distance from the inter tragal notch (e.g.,
within 5 mm of the eardrum).
Place patient at appropriate distance/azimuth from the
loudspeaker.
Select desired input level. (usually 60dB SPL)
Conduct the measurement
Clinical applications
Helps in determining appropriate vent size.
Indirect measure of occlusion effect.
Helps in selecting an acoustically appropriate sound
delivery system
 Real
ear saturation response
 Difference in decibels, as a function of
frequency, between the SPL at a specified
measurement point in the ear canal for a
specified sound field, with the hearing aid
(and its acoustic coupling) in place and
turned on. The measurement is obtained
with the stimulus levels sufficiently intense
as to operate the hearing aid at its maximum
output level.
 It is very critical measurement for children
and non responsive patients when the
maximum output of the hearing aid must not
only comfortable but also safe.
 Procedure:
 Same
as that of REAR, ensure that the
hearing aid is in saturation. This can be
accomplished by setting the input as 90dBSPL
and by adjusting the hearing aid volume
control to a just below the feedback.
 Clinical applications
 To measure the patient discomfort level
 To make sure that the maximum output of
the hearing aid is both comfortable and safe.
 Procedure
given later


Real ear to dial difference (REDD)
The difference between the outputs measured in dB SPL using a
probe microphone near to the ear drum to the measure made in
dB hearing level (HL) from a calibrated audiometer.

It usually requires an audiometer to produce the signal in dB HL
and the real ear analyzer and measure the response near the
eardrum in dB SPL.

Here continuous pure tone signal is usually produced from the
audiometer at 70dB HL using headphone or insert as the
transducer (which used to measure the patient threshold values).

The real ear analyzer measures the response near the ear drum
with the probe microphone. The difference between the SPL
value measured by real ear analyzer and the amplitude produced
by the audiometer in dB HL is the REDD at that frequency.
 We
obtain information across frequencies
 It is not necessary to mask the other ear.
 REG can be done for whom behavioral
responses are not available.
 The effects of input level are assessed.
 Sound
field is any area in which sound waves
are present
 Functional gain: is the dB difference
between aided and unaided behavioral or
neural thresholds
 EQUIPMENT
 The equipment used in sound field
measurements consists of a stimulus
generator, loudspeakers, and calibration
equipment.
 A.
Loudspeakers
 The ideal loudspeaker for audio logic testing
should possess the following general
characteristics:
 (a) Broad bandwidth (minimally 100–10,000
Hz);
 (b) Constant output as a function of
frequency (c) low distortion;
 (d) Capability of accurately transducing
transient as well as steady-state signals;
 B.ENVIORNMENT
 Sound
field measurements are influenced by
the acoustic characteristics of the
environment in which auditory measures are
to be conducted.
 When pure tones are introduced into the
sound field, the resonances of the room are
evidenced by standing-wave patterns with
resultant variation in measured SPL
depending on measurement location in the
room.
 Hence, warble tones
 To
achieve a reliable and repeatable
measurements in a sound field, it is
necessary to place the patient in an area
where ambient noise levels are controlled.
 Less reverberant condition
 Good absorbing material that dampens the
sound and reduces standing waves.
 Patient
placement in a sound field
 Patient
should be placed far enough from
reflecting surfaces so that there is no
disturbance from changes in sound pressure.
 Patient
be placed 1 m from the sound field
speaker to reduce the influence of standing
waves. The patients head must be held as
steady as possible.
 Frequency
specific stimuli- pure-tones have
problem of standing waves
 Hence, warble tones need to be used
 Speech
stimuli should also be used – to assess
the utility to understand conversational
speech under a variety of listening situations.
 Depending the age Ling sound test or
 Picture Identification testing or Word
Recognition testing should be done
 Its
also important to judge the intelligibility
of a paragraph/sentences using paired
comparison procedures.
 Finally,
loudness discomfort levels need to be
estimated
Functional Gain measurements
 It is a subjective method using sound field
measurements
 Functional gain can also be measured using
other objective methods such as ABR, ASSr
 Subject’s preferences and comfort levels can
be measured using this
 It
is a Real ear measure
 It is an objective method and less time
consuming
 Subject’s preferences and comfort levels can
not be measured using this
 This can be used to assess at different
stimulus level
 Verification
is an important component of
the hearing aid evaluation, but it does
evaluate whether the matched hearing aid
targets are actually appropriate for the
patient with regard to improvements in
speech perception, or whether the patient
will benefit from such prescribed hearing aid
gain.
 Hearing aid validation refers to outcome
measures designed to assess treatment
efficacy, that is, whether the hearing aids
are beneficial.
There are two types of validation/outcome
measures
 Subjective outcome measures use
questionnaires and interviews
 There are several questionnaires developed.
Some are:
 The Client Orient Scale of Improvement
(COSI) -Dillon, James, & Ginis, 1997
 The Glasgow hearing aid benefit profileGatehouse, 1998)
 Abbreviated Profile of Hearing Aid Benefit
(APHAB)- Cox & Alexander, 1995
1. The Glasgow
Benefit Inventory
(GBI)
Questionnaire
(Gatehouse, 1999)
2.Client Oriented
Scale of
Improvement (COSI)
(Dillon, James, & Ginis,
1997
3.International
outcome inventory
of hearing aids(IOIHA)
general
(12
All these scores
from –100 to +100.
range
The GBI contains
18 questions
regarding change
in health status
which assess how
the intervention has
altered the quality
of life of the person
a
subscale,
questions
Report the degree of
benefit obtained
compared to that
expected for the
population in similar
listening situations.
The goal of the
COSI is for the
patient to target up
to five specific
listening situations
Various categories
ranging from worse 148
to almost always ,
is a close ended
self benefit sevenitem questionnaire
which measures
hearing aid benefit
in seven
unidirectional
outcome domains.
Five point rating
scale
social
support
subscale,
(3
questions)
a physical health
subscale,
(3
questions)
Abbreviated Profile
of Hearing Aid
Benefit: APHAB
(Robyn M. Cox and
Genevieve C.
Alexander 1995)
Hearing Aid
Performance
Inventory
(Walden,
Demorest,
Helper, 1984)
24 items were
extracted from the
PHAB and
constructed into an
APHAB.
designed for use
in the hearing
instrument
verification
process. It
& consists of 64
items designed to
assess hearing aid
benefit in a
variety of
listening
situations across
a wide range of
ages.
Ease of
Communication
(EC)
Reverberations (RV)
Background Noise
(BN)
Aversiveness of
sounds (AV)
Percentile
scoring
1.Noisy situation
2.Quiet situations with
speakers in proximity
3.Situations with
reduced signal
information
4.Situations with no
speech stimuli
The
patient
chooses from a 5
item
scale,
ranging
from
“very helpful (1)
to
“hinders
performance” (5)
149
Hearing
Handicap
Inventory for
the Elderly
(HHIE)
The HHIE was
published by
Ventry and
Weinstein in
1982
The
HHIE
is
composed of 25
questions.
All
questions
are
labeled according
to the scale to
which they pertain
The
HHIE
is
composed of two
subscales, Social
(S) and emotional
(E).
The
emotional scale
estimates
the
patient’s attitudes
and
emotional
responses to his
or her hearing
loss. The social
scale measures
the
perceived
effects of hearing
loss in a variety
of
social
situations.
There is a three
point
scale
responses
system, “yes” (4
points),
“sometimes”
(2
points), “no” /”not
applicable”
(0points).
The
maximum score
is
100
and
minimum is 0.
Higher the score,
greater is the
perceived
handicap.
150
The Speech, Spatial and Qualities of Hearing Scale (SSQ)
●
The Speech, Spatial and Qualities of Hearing Scale (SSQ)is designed to measure a
range of hearing disabilities across several domains.
●
Particular attention is given to hearing speech in a variety of competing contexts,
and to the directional, distance and movement components of spatial hearing.
●
In addition, the abilities both to segregate sounds and to attend to simultaneous
speech streams are assessed, reflecting the reality of hearing in the everyday
world.
●
Qualities of hearing experience include ease of listening, and the naturalness,
clarity and identifiability of different speakers, different musical pieces and
instruments, and different everyday sounds
●
SSQ ratings were compared with an independent measure of handicap.
151
152
Self
assessment of
hearing
handicap: a few
audiological
and
non
audiological
correlates
Vanaja
(2000)
C.
S.
Questionnaire
was divided into
three
major
subscales:
A)
speech
understanding, B)
awareness
and
C)
emotional
subscales.
50 items in the
questionnaire
assessed
the
hearing handicap
of the individual
in
various
situations
such
as
familiar/unfamiliar
,
noisy/quiet,
with/without
visual cue.
A three point
rating scale was
used to quantify
the answer given
to each question.
A score of 0
indicated
no
handicap and 2
indicated
maximum
handicap.
153
 Objective
outcome measures
 Use speech perception and speech in noise
tests to check the improvement.
 HINT
 SIN
 QUICKSIN
 Indian Languages

Behavioural audiometry is not viable until the age of
5 to 6 months and, in some infants or young children
with developmental delay, not possible at all.

Difficult-to-test populations, hearing thresholds can
be obtained only through electrophysiological
measures that do not require any voluntary response
from the individual

Electrophysiological tests can assist research involved
in the adaptation (improvement) of hearing aids,
because these tests can measure auditory function
objectively

By placing the HA on a child and measuring the AR in the
contra lateral ear with a 65 dB SPL speech input, volume
control can be lowered or raised until the reflex is barely
observed. The optimum setting can be made by setting the
VC at a level just below the occurrence of the AR.

The difference between the aided and unaided reflex
threshold is the real ear or use gain at a particular volume
control setting.

Can also find out dynamic range (PT threshold-reflex
threshold)

And also LDLS can be predicted using Immittance since the
ART and loudness discomfort level for some types of
acoustic stimuli - especially speech - were at
approximately the same levels.

Level at which OAE is recorded cannot be used
to predict behavioural thresholds from which to
prescribe amplification.

However, the presence of OAEs or CMs suggests
normal outer hair cell function (mainly in the
cases of AD), which means amplification may
cause noise-induced hearing loss due to OHC
damage.

As a result it is important to monitor the child
for progressive hearing loss. This could
potentially be achieved using OAE tests.
Present the signal through the speaker
Carry out unaided ABR
Fit the hearing aid and record the aided ABR
Threshold, amplitude or latency of wave V can be used to fit
the hearing aid
1) Threshold of wave V.

The hearing aids and/or settings which provide lowest
threshold is selected
Krebs (1976); Cox and Metz (1980) and Kilney (1982)
2) Latency of wave V.


The hearing aids and/or settings which provide shortest
latency is selected
L-I function

The observed patterns could be used to
determine what type of HA would best suit a HL.

For instance, if Steeper than normal LI function
was a sign of recruitment (i.e., reduced dynamic
range) and that subject would benefit from
compression circuitry. Hecox (1983)
3) Gain of hearing aid can be adjusted till a
recognizable wave is obtained

Kiessling (1983) – has given Amplitude projection
procedure based on amplitude- intensity
function
 Threshold
gives gain, Amplitude growth
function gives DR & Compression.

Click stimulus -brief stimulus can be distorted and create
ringing in the hearing aid

Click stimuli are broadband and thus do not represent accurate
measures of hearing thresholds for any specific frequency

Hearing aids reacts differently to rapidly changing stimuli than
to continuous stimulus which leads to distortion of the stimulus

Brief stimuli may not activate the hearing instruments
compression circuitry in the same way as longer duration
There has not been much success in discovering valid ABR
measures to assess HAs
Even tone bursts can create a large artifacts with hearing aids



Studies (for example Picton et al (1998)) suggested that
it would be possible to measure functional gain of
hearing aids on the basis of ASSR threshold.
Damarla & Manjula, 2007
 studied the relationship between the real ear insertion
gain (REIG) and ASSR gain (unaided ASSR threshold vs.
aided ASSR threshold).


that ASSR gain and REIG were highly correlated and
there was no significant difference at all test
frequencies.
Amplitude Projection Procedure has been applied on
the ASSR data and ASSR could be used for selection
of gain and compression ratio.
 The
estimation error of hearing thresholds
from ASSR can be very large
It has been found that aided LLR responses are larger than
unaided responses when stimuli were presented at the same
input level.
The cortical responses are present reliably with speech stimuli
in aided infants with moderate and severe hearing losses.
However, can be present even in children with profound hearing
loss cases
the cortical responses’ shape changes consistently with changes
in the gain-frequency response of hearing aids.
Hence, LLR can be used to ensure that the hearing aid is useful
or not.
Presence of LLR indicates that the signal is audible and
perceived at the cortical level (verification)
It also monitors the change in neural processing of speech
(Validation)

The stimuli can be longer than the brief clicks or
tone pips that are needed to measure an ABR.
This means the hearing aid has time to react to
the sound

It can be done with speech stimuli and provide
information regarding speech processing.

It assesses almost the entire auditory system
Limitation: Arousal state affects the results.
 Aided
 The
MMN and P300 have been studied
results of this tell us about the
improvements in speech discrimination
ability with hearing aids.
 Counseling
and training