Pure tone audiometry is a test used to evaluate hearing thresholds across different frequencies. It involves presenting pure tones to a patient through headphones and determining the lowest volume they can detect at each frequency. Key information obtained includes the type, degree, and configuration of any hearing loss. PTA requires patient cooperation and provides an objective measure of hearing sensitivity. Proper testing conditions and techniques are important for accurate results.

1. AUDIOMETRY
Dr. Ashly Alexander
ENT PG Resident
GMC, Bhopal

2. TYPES
• SUBJECTIVE
Requires active cooperation of the
subject
Ex:
Pure tone audiometry
Speech audiometry
Bekesy audiometry
• OBJECTIVE
Based on physical, acoustic or
electrophysiological measurements
without depending on subjective
responses & cooperation
Ex:
Impedance audiometry
BERA
OAE
Electrocochleography

3. HEARING LOSS
1. Conductive hearing loss- caused by any disease process,
interfering with conduction of sound, from external ear to
the stepidio-vestibular joint.
2. Sensorineural hearing loss-
sensory- lesion of cochlea
neural- VIII nerve & its central connection
retro cochlear- lesion of VIII nerve
central- lesion of central auditory connection
3. Mixed hearing loss- both conductive & SNHL in same ear.

4. PURE TONE AUDIOMETRY

5. PURE TONE AUDIOMETRY
• Testing of hearing ability for pure tone with the help of an audiometer
• Hearing threshold is typically defined as the lowest (softest) sound level
needed for a person to detect a signal approximately 50% of the time
• Patients hearing threshold is measured in comparison to ideal fixed normal
hearing level (0 dB) and thus is a relative hearing threshold measurement.
• PTA requires active cooperation from subject

7. WHY PURETONE THRESHOLDS?
• The auditory system is organized tonotopically(i.e., a frequency-to place
mapping). That means, high frequencies are represented at the basal end and low
frequencies at the apical end.
• Damage to sensory cells of the cochlea at a specific place along the basilar
membrane can result in a loss of hearing that corresponds to the frequencies
coded by that place.
• For this reason, Pure tone threshold tests provide details that would
otherwise remain unknown if a broadband stimulus such as speech were
used.

8. USES
• To find out any hearing loss is present or not.
• Degree of hearing dysfunction.
• Type of hearing loss- Conductive or SNHL.
• To decide on the appropriate rehabilitation device which can be used to
minimise the hearing disability
• Gives credibility to the clinical tests.
• Establishes a baseline for any change( improvement or deterioration)
• A record can be kept for future reference.
• Audiogram is essential for prescription of hearing aid.

9. CALIBERATION
• The human ear does not perceive sound equally well at all frequencies.
• The ear is most sensitive to sound in the intermediate region from 1000 to
4000 Hz and is less sensitive at both the higher and lower frequencies.
• In normal ears more sound pressure is needed to elicit a threshold response at
250 Hz than at 2000 Hz.
• This curve representing hearing sensitivity is often referred to as the minimum
audibility curve.

10. CALIBERATION
• The audiometer is calibrated to
correct for these differences in
threshold sensitivity at various
frequencies
• Consequently, when the hearing level
dial is set at zero for a given
frequency, the signal is automatically
presented at the normal threshold
sound pressure level required for the
average young adult to hear that
particular frequency

11. • ISO1964specification
• Done once every 6months
• Biological calibration daily
• Digital audiometers- calibrations yearly
• Accessories should meet the accepted standard

12. COMPONENTS OF A PURETONE
AUDIOMETER
• Oscillator : The role of the oscillator in a Puretone audiometer is to generate
electronically standardized frequencies within +/- 3% of their nominal value. The
frequencies generated are 125,250, 500,750, 1000, 1500, 2000, 3000, 4000,
6000 and 8000 Hz.
• Interrupter switch : The tones presented to the patient should be switched
on and off. This feature is important because a continuous tone undergoes decay
during a period of time.
• Equalisation circuit : because the threshold of human hearing is not uniform
• Output power amplifier
• Hearing level attenuator: The attenuator can be varied in steps of 5 dB. The
basic reference point is marked as 'O'.
• Outpur transducers: Is of three different types. 1. Ear phones 2. Bone
vibrator 3. Loud speaker (free field audiometry(pediatric patients)

14. IDEAL ROOM SETUP
• Acoustically treated or sound isolated room
• Ambient sound is measured with sound level meter.
• One room or a two room set up required.
• Level of sound in Test Environment < < Level of Masking Sound
• Maximum permissible ambient noise for the different frequencies required for
air and bone conduction tests.
• Air Conduction - 25 - 30 db
• Bone Conduction- 10 -15 db

15. INSTRUCTIONS TO THE
PATIENT
• The patient is instructed to raise the index finger if the sound is heard. The
patient should respond even if the sound is faintly heard.
• Before placing the ear phones on the patient, the patient's ear should be
examined for the presence of wax.
• Improper placement of head phones will cause threshold variations of even 15 –
20 dB.

16. POSITION OF HEADPHONES
• The diaphragm of the headphone should be placed exactly over the opening of
the EAC
• Small plastic tube can be placed in EAC to prevent its collapse
• Insert ear phones can be used

17. Proper positioning
during pure-tone
audiometry carried out
with a single
soundtreated room for
(A) examiner, (B)
audiometer, and (C)
patient

19. PLACEMENT OF BONE CONDUCTION
VIBRATOR
Mastoid placement-
should be free from hair,
should be placed where sound appear loudest to the
subject.
should neither touch pinna nor ear phones
non test ear should be masked
Tension of spring metal headband over the mastoid - 500
gm / sq.cm
Frontal placement
placed on the forehead over frontal bone
superior to mastoid placement due to fewer variations
produced by vibrator to skull pressure & less artifact
produced but is less sensitive

20. TECHNIQUE OF MEASUREMENT
• Some audiologists assess the threshold of air conduction by going from an
inaudible to an audible stimulus intensity. This method is known as ascending
method of estimation of threshold of hearing.
Assessing the threshold of air conduction by going from an audible to an
inaudible stimulus intensity is known as descending method of threshold
estimation.

21. TECHNIQUE OF RECORDING AIR
CONDUCTION THRESHOLD
• Most commonly used is Conventional Hughson & Westlake technique (modified
by Carhart and Jerger).
• ASHA-American Speech & Hearing Association
• British Association of Otolaryngologist procedure
• International Standards Organization procedure.

22. HUGHSON & WESTLAKE
TECHNIQUE
• Complete history and examination
• Better ear tested first.
• 1000 Hz 2000 4000 8000 10,000 1000 500 250 Hz
• If difference between these octaves is >20dB then half octaves i.e. 750, 3000, 6000 Hz
tested.
• Start with arbitrary supra threshold level. (Descending method)
• "Up 5-down 10" method of threshold estimation:
• The starting intensity of the test tone is reduced in 10 dB steps following each positive
response, until a hearing threshold level is reached at which the subject fails to respond.
Then, the tone is raised by 5 dB, if the subject hears this increment, the tone is reduced by
10 dB; if the tone is not heard then it is raised by another 5 dB increment. This 5 dB
increment is always used if the preceding tone is not heard, and a 10 dB decrement is always
used when the sound is heard.

23. • Red line for right ear
• Blue line for left ear
• Continuous line for air conduction
• Broken line for bone conduction

24. WHAT IS PURE TONE AVERAGE ?
• It is the average of hearing thresholds at 500, 1000 & 2000 Hz and is
helpful in calculating hearing disability of the patient.

25. CROSS HEARING
• Cross hearing occurs when a stimulus presented to the test ear “crosses over”
and is perceived in the nontest ear.
• Cross hearing is the result of limited interaural attenuation(IA).
• IA refers to the “reduction of energy between ears.” Generally, it represents
the amount of separation or the degree of isolation between ears during testing.
Specifically, it is the decibel difference between the hearing level (HL) of the
signal at the test ear and the HL reaching the nontest ear: IA = dBHLTestEar –
dBHL NontestEar

27. SHADOW CURVE
• The cochlea of the non test ear gets
stimulated by the sound that is
meant to test the test ear and false
threshold of the test ear is obtained.
• This false threshold if plotted for
the different frequencies will result
in a curve which actually shadows the
threshold of the better ear and is
termed as shadow curve

28. MASKING
• Masking is defined as a procedure where measured
quantities of noise is delivered to the non test ear to
prevent participation of the non test ear.

29. TYPES OF MASKERS
• White noise : Broadband or wideband noise (has the same sound intensity at all
frequencies)
• Pink noise: pink noise decreases in intensity as the frequency goes up
• Critical band noise: Narrow band of noise centered on test tone freq. with 100 – 200
Hz above and below that freq. Used in pure tone audiometry
• Speech noise : noise having frequency in speech range (300 – 3000 Hz )
• Complex noise: Low freq. fundamentals plus the multiples of that freq. up to 4000 Hz

30. • Pink noise • White noise

31. WHEN TO USE MASKING
• For all bone conduction - bones of skull transfer sound very
efficiently (interaural attenuation for BC = 0)
• For air conduction masking need to be done only if the
difference between the thresholds of two sides is more than
40 db

32. EXAMPLES
Normal-hearing Sensitivity

33. CONDUCTIVE HEARING LOSS
Normal BC thresholds (<20 db)
Increased AC thresholds (>30db)
AB gap (>25db)

34. SENSORINEURAL HEARING LOSS.
 Both air (>30db) and bone
conduction(>20 db) thresholds
are raised
 No AB gap (<20db)
 Bilateral sloping (decending)
curve in presbyacusis

35. MIXED HEARING LOSS
• AC Threshold > 45db
• BC Threshold >20 db
• AB gap >20 db

36. NOISE INDUCED HEARING LOSS.
• The audiogram in NIHL shows a
typical notch, ACOUSTIC DIP or
BOILER MAKER’S NOTCH, at 4 kHz,
both for air and bone conduction. It is
usually symmetrical on both sides.

37. MÉNIÈRE’S DISEASE.
• Hearing loss is sensorineural and
more in lower frequencies—the rising
curve. As the disease progresses,
middle and higher frequencies get
involved and audiogram becomes flat or
falling type.

38. OTOSCLEROSIS
• Pure tone audiometry shows loss of
air conduction, more for lower
frequencies.
• Bone conduction is normal. In some
cases, there is a dip in bone
conduction curve.
• It is different at different
frequencies but maximum at 2000 Hz
and is called Carhart’s notch (5 dB at
500 Hz, 10 dB at 1000 Hz, 15 dB at
2000 Hz and 5 dB at 4000 Hz)
(Figure ). Carhart’s notch disappears
after successful stapedectomy

39. CONGENITAL DEAFNESS
• Trough shaped (U or basin shaped
audiogram)- cookie bite audiogram

40. WHO CLASSIFICATION OF
HEARING LOSS
• MILD 26-40dB
• MODERATE 41-55dB
• MODERATELY SEVERE 56-70dB
• SEVERE 71-90dB
• PROFOUND >91dB

41. WHAT IS HIGH FREQUENCY
AUDIOMETRY?
• Conventional audiometry tests hearing thresholds between 250-8000 Hz
• In certain conditions of SNHL higher frequencies may be involved initially.
• High frequency audiometry tests between 8000-20000 Hz
• Classical indications: ototoxicity & noise induced hearing loss

42. • Audiogram are very often inaccurate
• Improper technique
• Improper test condition
• Improper test instrument
• Improper examiner
• Subjective & time consuming test
• Does not assess the main features of hearing- frequency discrimination &
temporal resolution of sound.
• Results may vary from set up to set up.
DRAWBACKS OF PTA

44. IMPEDANCE AUDIOMETRY

45. IMPEDANCE AUDIOMETRY
• It is an objective test, widely used in clinical practice and is particularly useful
in children.
• It consists of:
(a) Tympanometry
(b) Acoustic reflex measurements

47. TYMPANOMETRY
• Measures the compliance of tympano-ossicular system reflecting the status of
middle ear
• It is based on a simple principle, i.e. when a sound strikes tympanic membrane,
some of the sound energy is absorbed while the rest is reflected. A stiffer
tympanic membrane would reflect more of sound energy than a compliant one.
• By changing the pressures in a sealed external auditory canal and then
measuring the reflected sound energy, it is possible to find the compliance or
stiffness of the tympano-ossicular system and thus find the healthy or
diseased status of the middle ear.

48. • The equipment consists of a probe
which snugly fits into the external
auditory canal and has three channels:
(i) to deliver a tone of 220 Hz by a
mini loudspeaker,
(ii) to pick up the reflected sound
through a microphone and
(iii) to bring about changes in air
pressure in the ear canal from positive
to normal and then negative by a
manometer
Ear in which probe is connected = probe ear
Other ear is to deliver PTA/noise to measure stapedial reflex = phone ear

49. TYMPANOMETRY

50. • Probe tip is placed in ear, seal maintained
• Inducing a pressure of +200daPa
• Then pressure is reduced to +100 then to 0 such that from max stiffness to
max compliance
• Then pressure is reduced to -100 then to -200daPa
• Impedance is recorded graphically at various pressure conditions
TYMPANOMETRY - PROCEDURE

51. TYMPANOGRAMS
Type A: Normal
Type As: Compliance is lower at or near
ambient air pressure. Seen in fixation of
ossicles,
e.g. otosclerosis
malleus fixation,
Tympanosclerosis
Congenital fixation of footplate
Osteoarthritis of the
incudomalleolar joint
Thick graft myringoplasty

52. TYMPANOGRAMS
Type Ad: High compliance at or near
ambient pressure.
Seen in ossicular discontinuity or
thin and lax tympanic membrane.
Type B :A flat or dome-shaped graph.
No change in compliance with pressure
changes.
• Otitis media with effusion,
• space-occupying lesions of the
tympanic cavity,
• tympanic membrane perforations
• Probe tip not placed properly
• Impacted wax
• Thick TM
• Patent grommet

53. TYMPANOGRAMS
Type C: Maximum compliance occurs
with negative pressure in excess of
100 mm H2O. Seen in eustachian tube
dysfunction & retracted tympanic
membrane.
• Type D curve: which shows a notch in
the pressure peak, is often seen with
scarred eardrums or with normal,
hypermobile eardrums.

56. ACOUSTIC REFLEX
• It is based on the fact that a loud sound, 70–100 dB above the threshold of
hearing of a particular ear, causes bilateral contraction of the stapedial
muscles which can be detected by tympanometry.
• Afferent limb- 8th nerve, centre- SON, efferent limb- 7th nerve
• Tone can be delivered to one ear and the reflex picked from the same or the
contralateral ear.
• Normal reaction time- 120ms at 1000 Hz & 140 ms at 2000 Hz

57. PATHWAY

59. 1.To test the hearing in infants and young children.
2.To find malingerers.
A person who feigns total deafness and does not give any response on pure
tone audiometry but shows a positive stapedial reflex is a malingerer.
3.To detect cochlear pathology.
Presence of stapedial reflex at lower intensities, e.g. 40– 60 dB than the
usual 70 dB indicates recruitment and thus a cochlear type of hearing loss
4.To detect 8th nerve lesion.
If a sustained tone of 500 or 1000 Hz, delivered 10 dB above acoustic
reflex threshold, for a period of 10 s, brings the reflex amplitude to 50%, it
shows abnormal adaptation and is indicative of 8th nerve lesion (stapedial
reflex decay).
CLINICAL USES

60. CLINICAL USES
5. Lesions of facial nerve.(topognosis)
Absence of stapedial reflex when hearing is normal indicates lesion of the
facial nerve, proximal to the nerve to stapedius. The reflex can also be
used to find prognosis of facial paralysis as the appearance of reflex,
after it was absent, indicates return of function and a favourable
prognosis.
6. Lesion of brainstem.
If ipsilateral reflex is present but the contralateral reflex is absent,
lesion is in the area of crossed pathways in the brainstem.
7.Otosclerosis
Reflex cannot be recorded due to stapedial fixity

61. • WILLIAM’S TEST-the audiometer is programmed to measure the pressure
changes at the start of test; after patient swallows; after performing valsalva.
• Resting middle ear pressure should be near normal, with swallowing become
negative & positive on performing valsalva.
• This test is applicable only for intact tympanic membrane.
EUSTACHIAN TUBE FUNCTION
TEST

63. • Toynbee’s test-done in patients with perforated TM
• Audiometer is programmed to increase or decrease pressure in the middle ear and then
measure the pressure changes each time the patient swallows.
• Patient swallows 5 times-
If falls to 0 –patent eustachian tube
If pressure doesn’t fall to 0 by 5 swallows- partial dysfunction
If doesn’t fallow/change on swallowing- eusctachian tube dysfunction
EUSTACHIAN TUBE FUNCTION
TEST

64. EUSTACHIAN TUBE FUNCTION TEST
TOYNBEE’S TEST

65. EVOKED RESPONSE AUDIOMETRY

66. EVOKED RESPONSE
AUDIOMETRY
• Objective test
• Measure electrical activity in the auditory pathways in response to auditory
stimuli
• Requires special equipment with an averaging computer
• Two components of evoked electric response have gained clinical acceptance
Electrocochleography
Auditory brainstem response

67. BRAINSTEM EVOKED RESPONSE
(BERA)
• Also known as brain stem auditory evoked response or
potential(BAEP)
• Far field recording of neuroelectric activity of the eight nerve &
brainstem auditory pathways that occur over the first 10
milliseconds after a suitable sound stimulus has been delivered to
the ear
• Designated as far field recording because of relatively larger
distance between the recording electrode on the scalp and the
actual generators of the response in the brainstem.

68. BERA
• This investigation was first described by Jewett and Williston in 1971
• Potential evoked by sound is called BERA or Jewett Bumps
• Non-invasive technique to find the integrity of central auditory pathway
through the VIIIth nerve, Pons ,and midbrain.
• Never a substitute for other audiological tests

70. • Electrodes
• Reference electrode- ear to be tested
• Active electrode- vertex/forehead
• Ground electrode- opposite ear
Acoustically treated & electrically protected room
Electrical potential are generated in form of several clicks stimuli and tone bursts i.e
1000-2000clicks at a rate of 5-50/sec and picked up from surface electrodes.
Neurogenic potential is recorded by the computer

71. Measure hearing sensitivity in the range of 1000 – 4000 HZ.
In normal persons 7 waves are produced in first 10 sec.
The 1st , 3rd , 5th , wave are most stable and are used for measurement
Waves are studied for – absolute latency
interwave latency (between 1 & 5 )
amplitude

72. BERA
• Wave I-generated from 8th nerve distal part
• Wave II-generated from proximal part of 8th nerve
• Wave III-generated from cochlear nuclei
• Wave IV--generated from superior olivary complex
• Wave V-generated from lateral lemniscus & inferior
colliculus
• Wave VI & VII – medial geniculate body

73. BERA WAVES

74. 1 ) ABSOLUTE LATENCY
Time of stimuli from onset to the peak of the wave. Prolongation means
hearing loss.
Normal values are:
 Wave I – 1.8 msec
 Wave II – 2.8 msec
 Wave III – 3.8 msec
 Wave IV – 4.8 msec
 Wave V - 5.8 msec

75. 2) INTERWAVE LATENCY
Conduction time between one wave to the other
Between wave 1 and wave 3
Between wave 3 and wave 5
Usually the value will be 2 msec. Not more than 2.4 sec .
Between wave 1 and wave 5 , value is 4.4 msec .

77. 3) AMPLITUDE RATIO
 Distance between the peak and trough
 Amplitude is directly proportional to intensity
 Amplitude ratio V/I = 1
 Normal ratio is 1
 Less than 0.75 is abnormal .

78. INTERPRETATION
• Wave I : small amplitude, delayed or absent may indicate cochlear lesion
• Wave V : small amplitude, delayed or absent may indicate upper brainstem
lesion
• I – III inter-peak latency (>2.3ms): prolongation may indicate lower
brainstem lesion.
• III – V inter-peak latency: prolongation may indicate upper brainstem lesion.
• I – V inter-peak latency: prolongation may indicate whole brainstem lesion.
Shortening of wave the interval with normal latency of wave V indicate cochlear
involvement.

79. INTERPRETATION
• Wave 1 present others absent confirms a retro cochlear involvement
• Wave 3 is most commonly absent wave
• In many clinics and laboratories a I–III IWI extending beyond 2.4 ms is considered abnormal
• The I–V IWI may also be used in the detection of vestibular schwannoma
• When Wave V latency measurements are greater than 6.1 ms, the possibility of an eighth nerve
tumor should be considered
• Wave V is the only wave of the ABR that is present in each ear confirm. So wave 5 is taken for
measurement-Change in 0.3 to 0.4 ms is diagnostic
• Wave 5:1 ratio is less than .75 is indicative of vestibular schwanommas
• When tumour is large, contralateral ABR wave 3 to 5 affected due to compression of tumour

80. USES
• As a screening procedure for infants (IOC for congenital
deafness)
• Determine threshold for hearing in a deaf child
• To diagnose retrocochlear pathology particularly acoustic
neuroma.
• To diagnose brainstem pathology –multiple sclerosis,pontine
tumors, brainstem stroke
• To monitor 8th nerve intra operatively in surgery of acoustic
neuroma to preserve the function of cochlear nerves
• Used to confirm brain death
• To rule out malingering
• Prognosis in neurological disorders

82. ELECTROCOCHLEOGRAPHY
• Electrical activity generated by cochlea and the auditory nerve in
response to auditory stimuli within first 5 minutes can be measured by a
system called electrocochleography.
• Parameters measured
• Cochlear microphonics (from outer hair cells)
• Summating potential (due to combined movement of hair cells & basilar
membrane)
• Auditory nerve compound action potential
• Electrode is placed
• Through the TM on promontory/round window
• Non invasively-over the TM or deep in the EAC
• Reference electrode is placed on mastoid or forehead

83. ECOCHG
• Stimulus- click’s, tone pips
• Graph with latency in milliseconds & amplitude in microvolts is plotted .
• Done under LA in adults ( apprehensive person and children – GA)
• Normally the ratio between the amplitude of summating potential to the
action potential is less then 20 % .
• Increase in ratio is indicative of meniere’s disease (>30%) .

85. GLYCEROL TEST
• First introduced by Klockhoff & Lindblom in 1966
• Glycerol is administered in doses of 1.5mg/kg body wt in empty stomach
• Serum osmolality should increase atleast by 10 mos/kg
• ECOCHG is performed after 1hr of administering glycerol
• Side effects- headache, nausea, vomiting & drowsiness

86. ELECTROCOCHLEOGRAPHY
Use-
Assessment & monitoring of meniere’s disease.
Helping in interpretation of BERA where wave I is not
identifiable .
Intra operative monitoring in neurotological procedures .
Ascertaining hearing threshold in difficult to test pts.

88. AUDITORY STEADY STATE
RESPONSE (ASSR)
• Electrophysiological test which uses continuous auditory stimulus (instead of
click stimuli in BERA)
• Steady state signals are modulated rapidly in amplitude and frequency and
thus give a frequency specific audiogram
• Measure of entire auditory pathway upto cortex
• Easier & more objective, can be done irrespective of age, mental state &
degree of hearing loss
• Detect hearing losses > 80 dB

89. ASSR
• Detect hearing sensitivity in severe to profoundly deaf infants
• Helps in selection of children for cochlear implantation at an early
age, in comatose pts & to r/o non organic hearing loss, central auditory
neuropathy
• In central auditory neuropathy if BERA is done, it will show profound
hearing loss but they are not a good candidate for cochlear
implantation as pathology is higher up. Therefore in such cases ASSR
is necessary.

91. OTOACOUSTIC EMISSION TEST

92. OTO ACOUSTIC EMISSION
• Discovered by David Kemp in 1978
• The sound emitted by the biological activity of the normal
cochlear outer hair cells which can be picked up, recorded &
measured by placing a microphone in the deep external meatus
is OAE.
• The emission are called Kemp echo’s or cochlear echo’s
• Preneural phenomenon
• Emission are present when outer hair are healthy and are
absent when they are damaged and thus help to test the
function of cochlea.
• Do not disappear in 8th nerve pathology .

93. OTOACOUSTIC EMISSIONS
• Otoacoustic Emissions are the sound that result from energy generated in
cochlea
• Propagated through middle ear
• Transmitted through External Auditory canal
• Captured by a microphone in External Auditory canal

95. PREREQUISITES
 Done in quite room
 No patient preparation
 Requires 10 -15 minutes
 Probe placed in the ear canal
 Fan or sound producing instrument switched off
 Child test done during asleep, Adult avoid movements and talk
 Not painful
 Non-invasive

96. TYPES
Spontaneous otoacoustic emission
(SOAE)
Evoked otoacoustic emission
Transient OAE
Distortion product OAE
Stimulus frequency OAE

97. TYPES
Spontaneous otoacoustic emission (SOAE):
 SOAEs are measured in the absence of external stimulation
 SOAEs appear as puretone-like signals coming from the ear.
 Present in healthy normal hearing person when hearing loss does not
exceed 30 dB.
 Absent in 50% of normal person.
 Considered as a screening test rather
than a diagnostic test
 More in females

98. EVOKED OTOACOUSTIC EMISSION :
TYPES
Transient evoked OAE(TOAE) –
• As their name suggests, TEOAEs are measured following the
presentation of a transient or brief stimulus.
• Series of click stimuli are presented at 80 – 85 dB SPL and
response recorded . Therefore, also called COAE or Click Evoked
OAE
• Best to detect hearing loss in 2k and 4k & best for neonatal
screening

100. EVOKED OTOACOUSTIC EMISSION
: TYPES
Distortion product OAE(DPOAE)-
• Two tones (called “primaries”) are simultaneously presented at two different
frequency & intensity levels to the cochlea to produce distortion product .
• The frequencies of the primaries are conventionally designated as “f1” and “f2”
(f1 < f2) and the corresponding levels of the primaries as “L1” and “L2.”
• OAE output are mathematically related to frequencies
2f1–f2 represents the cochlear function of f2 frequency region of the cochlea
• Used to test hearing in the range of 1000 to 8000 Hz .
• Used in early detection of cochlear damage(ototoxicity & NIHL)

102. EVOKED OTOACOUSTIC EMISSION :
TYPES
Stimulus frequency OAE:
• Occur at same frequency and at same time when a pure tone is
introduced into ear
• Not used routinely in clinical practice
• SFOAE equally efficient in finding hearing loss in 1k and 2k and superior
to other EOAE at .5k

103. INTERPRETATION
• Results are shown as PASS or REFER
• If REFER- repeat OAE after 2 wks,
if again REFER do BERA

104. USES OF OAE
• Screening of neonates for SN loss
• Detects cochlear and retro cochlear pathology
• Early changes of ototoxicity can be detected
• Early cases of noise induced hearing loss can be detected
• Monitoring meniere’s disease
• Tinnitus
• Rule out malingering
• Intraoperative monitoring

105. PITFALLS IN OAE?
• False negative: middle ear & external ear pathology
• Presence of OAE does not guarantee a normal neural pathway, confirmation of
which needs BERA

106. WHAT IS OAE SUPPRESSION?
• In the normal ear, evoked OAE can be suppressed by another acoustic
signal(suppressor) applied ipsilaterally or contralaterally
• The pathway for OAE suppression is from external canal to the cochlea,
afferent fibres to brainstem superior olivary nucleus & then to efferent medial
olivocochlear fibres back to both cochlea to suppress the evoked OAE & finally
back to the ear canal.
• Clinical importance: absence of OAE suppression in auditory neuropathy &
brainstem lesions

109. TEST FOR RETRO-COCHLEAR
PATHOLOGY

110. TONE DECAY TEST
• PRINCIPAL- pathology in the auditory nerve causes an abnormally rapid
deterioration in the threshold of a tone if that tone is presented
continuously to the ear
• Measure of nerve fatigue and used to detect retrocochlear lesions .
• Normal person can hear a tone continously for 60 sec .
• In Nerve fatigue he stops hearing earlier
• Electrophysiology- Wedensky’s peripheral nerve inhibition

111. CARHART’S METHOD OF TONE
DECAY TEST
Pure tone of 4k Hz is presented at 5 dB above the patients threshold of hearing,
continuously for a period of 60 sec
If patients stop hearing earlier intensity is increased by another 5 dB
Procedure is continued till patients can hear the tone continuously for 60 sec or no
level exist above the threshold where tone is audible for full 60 sec .
Result is expressed as number of decibel of decay .
A decay more than 25 dB diagnostic of retrocochlear lesion.

112. • Decay is normal-0 to 5dB (INCREMENT)
• Mild decay-10 to 15dB
• Moderate- 20 to 25
• Severe -30dB or more =highly suggestive of
retro cochlea pathology

113. TEST FOR COCHLEAR PATHOLOGY

114. RECRUITMENT
Term coined by Fowler in 1937
Recruitment is abnormal growth of sound or non-linear growth of loudness,
which is a hallmark of cochlear pathology
Patients with recruitment are poor candidates for hearing aids.
Tests for recruitment
• Absolute binaural loudness balance test(ABLB)
• Short increment sensitivity index (SISI)
• Loudness discomfort level
• Differential liamen test

115. ABLB TEST-FOWLER’S TEST
Alternate binaural loudness balance test
Test is done in cases with unilateral pathology
Frequency used 500 or 1000Hz
Hearing threshold for the above frequency in both ears is
ascertained
Attenuator dial is set such that worse ear is at 20dB above
hearing threshold
Better ear at hearing threshold
ABLB function is started in the audiometer such that tones
alternate between two ears & pt asked to indicate in which ear
sound appears louder

116. ABLB
• If the tone is louder in the worse ear, tone in better ear is raised by 5dB
• If the tone is lesser in the worse ear, tone in the better ear is reduced by 5dB
• This process is done till the sound is equal in both ears
• This whole process is repeated at 10dB increments for the worse ear & the
level of tone in the better ear equal in loudness is recorded
• Plotted in the form of a Laddergram

117. LADDERGRAM

118. INTERPRETATION OF ABLB
• Absence of recruitment-for equal loudness levels in the two ears,
the difference in the hearing level will remain constant no matter
what be the intensity of the sound.
• Complete recruitment-when there is equal loudness at equal
intensities=cochlear pathology
• Partial recruitment- the difference in the hearing level between
the two ears for equal loudness sensation, gradually diminishes with
increasing intensities but the difference never becomes zero.
• Loudness reversal- the growth in loudness in the deafer ear is
slower than that in the better ear then decruitment is said to exist.

120. SHORT INCREMENT SENSITIVITY
INDEX (SISI TEST)
• SISI test determines the capacity of a patient to detect a
brief 1dB increment in a 20 dB suprathreshold tone at various
frequencies
• Patient with cochlear lesion distinguish smaller changes in
intensity than normal persons and those with conductive
deafness and retrocochlear pathology.
• Generally test is done between 1000 to 4000Hz
• Continuous tone 20dB above threshold is presented and
sustained for about 2 min.

121. SISI
SISI apparatus is adjusted such that every
5seconds there is a 1dB increment in the carrier
tone
Twenty such blips are then presented & the
number of correctly identified responses noted.
This multiplied by 5 gives percentage SISI score.
70-100%=cochlear lesion
65 -25%=questionable significance
0-20%=retrocochlear lesion/ normal/Conductive
Deafness

123. SPEECH AUDIOMETRY

124. SPEECH AUDIOMETRY
Use to assess hearing sensitivity of a subject for
speech
Use of speech audiometry to the neurotologist is in the
identification of neural types of hearing loss , in
which both the reception as well as the discrimination
of speech is impaired.
2 parameter:- 1 ) Speech reception threshold
(SRT)
2 ) Speech discrimination score (SDS)

125. SPEECH RECEPTION THRESHOLD
Minimum intensity at which 50%of the words are repeated correctly by the
patient.
A set of spondee words delivered to each ear
Spondaic words are 2-syllable words spoken with equal emphasis on each
syllable (eg, pancake, hardware, playground).
Present group of 6 spondee words at a step 25db above pure tone hearing
threshold then sucessive lower intensities till subject correctly identifies 3
out of 6 words.
Normal and conductive hearing loss:- SRT within 10 db of average of pure
tone threshold
Neural deafness:- higher than pure tone average
.

126. SPEECH DISCRIMINATION SCORE
(SDS)
• The percentage of correctly identified words when words from a specially
prepared list called “phonetically balanced words list” is presented to the
subject.
• 50 words from PB list are presented at 35dB above SRT.
• SDS= No. of correctly identified words x 2
• 90-100% normal. Score is considerably low in neural pathology.

127. SD Score Ability to understand
speech
90-100% Normal
76-88% Slight difficulty
60-74% Moderate difficulty
40-58% Poor
<40% very poor

128. SPEECH AUDIOGRAM

129. ROLL OVER PHENOMENA
Seen in retrocochlear hearing loss.
Increase in speech intensity above a particular level, PBmax score
falls rather than maintaining a plateau as in cochlear type of
hearing loss

130. APPLICATION
1 Find SRT which correlates well with average of pure tone frequency.
2 Differentiate organic from nonorganic (functional) hearing loss.
3 Helpful for fitting hearing aid and setting its volume.
4 Differentiate cochlear from retrocochlear sensorineural hearing loss.
5 Assessment of degree and type of hearing loss
6 Examination of word recognition abilities
7 Examination of discomfort or tolerance to speech stimuli

131. BEKESY AUDIOMETRY
Self recording audiometer is used in which the changes in intensity as well as
frequency are done automatically by means of a motor.
Two tracings are recorded for each ear-one is continuous other with pulsed
tone.
By noting the relationship between the tracing Jerger classified Bekesy
tracings into 5 different patterns which help to localize the site of lesion

132. TRACINGS
Type I - Continuous and pulse tracing overlaps.
normal/conductive hearing loss
Type II- Both tracing overlaps upto 1000HZ, then the continuous tracing falls
cochlear hearing loss
Type III- continuous trace falls rapidly away
retrocochlear/neural hearing loss
Type IV- Continuous tracing falls at frequency up to 1000HZ
retrocochlear/neural hearing loss
Type V - Continuous tracing above pulse tracing
non organic hearing loss

134. TEST COCHLEAR RETRO-COCHLEAR
PTA SNHL SNHL
SPEECH DISCRIMINATION SCORE <90 % VERY POOR
ROLL OVER PHENOMENON ABSENT PRESENT
RECRUITMENT PRESENT ABSENT
ABLB TEST CONVERGING DIVERGING
SISI TEST OVER 70 % 0-20 %
THRESHOLD TONE DECAY TEST <25 db >25 db
STAPEDIAL REFLEX REFLEX AT < 60 db
(DECAY ABSENT)
REFLEX AT >70 db
(DECAY PRESENT)
BERA (WAVE V LATENCY) <4.2ms >4.2ms

135. AUDIOMETRY IN CHILDREN
• Below 3 months- child is only startled by loud sounds
• 5-6 months- child acquires power of localizing sound & turns the eyes/head
towards the sound source
• Power of localization is initially for noise(like a rattle), then speech sound &
finally at 9-10 months for pure tone sounds.
• At 9 months- responds to name calling
• At 12 months- can utter few meaningful words
• At 18 months- child learns to respond to commands & auditory cues, also reacts
to sound from any direction
• At 24 months- child can be conditioned by auditory cues & has a vocabulary of
20+ words

136. 0-4 MONTHS
• Auropalpebral reflex- blinking/ tightening of eyelids in response to loud sounds
of 50-70bd
• Startle reflex- sudden movements or small jumps of infants body immediately
on presenting loud sound
• Arousal reflex-sudden arousal of a quiet & partially sleeping child on exposure
to a loud sound
Keep in mind that the first response is usually the correct response as these
tend to disappear on repetition.

137. AFTER 5-6 MONTHS
• Free field audiometry
• Visual reinforcement audiometry
• Distraction test

138. FREE FIELD AUDIOMETRY
• Child is placed between 2 calibrated loudspeakers in a sound treated room
• Tested whether the child is turning the head to the direction of the
loudspeaker from which sound is coming
• By gradually lowering the intensity of sound rough estimation of hearing
threshold can be obtained
• Main problem- child becomes inattentive & looses attention after some time

140. VISUAL REINFORCEMENT
AUDIOMETRY
• Similar to free field audiometry
• A moving toy is placed over the loudspeakers
• Every time the child hears the sound from one loudspeaker and looks towards it – the
toy kept above it is activated for a short duration
• This reinforces the child’s responses & helps to sustain interest
• Sound given -
25 db for 6-10 months
20 db for 13-17 months
15 db for 18-23 months
10 db for 24-29 months

142. DISTRACTION TEST
Done between 6-24 months, 2 persons are required for the test
1 distractor – keeps the child distracted with some toys or gestures so that child
is mentally involved
& 2nd examiner- presents the sound from behind & records the child’s response
PROCEDURE
• Child sits on mothers lap looking the distractor while examiner stands 2 feet
behind the child 45 degree to one side
• Distracter keeps the child distracted for some while & briefly suspends the
activity for a moment
• Examiner presents a sound from behind at the very moment
• If child responds by turning the head- assumed that child has heard the sound

144. 2-5 YEARS
Play audiometry
• Here child is conditioned i.e taught a response to respond to sound stimulus
whenever the child hears the sound
• Hearing threshold for different frequencies for both ear separately can be
measured & also air and bone conduction test can be done
• Subjective response
PTA can only be done reliably after atleast 5 yrs of age
Before this age- play audiometry + BERA is the best option

146. NON ORGANIC HEARING LOSS

147. NON ORGANIC HEARING LOSS
• Apparent hearing loss with no evidence of known disorder or insufficient
evidence to explain it
• Its of 2 types:
1. Psychogenic (conversion deafness)- due to psychological conditions, pt
not aware of deafness.
2.Malingering
Person consciously pretending to be deaf. It occurs & disappears suddenly.

148. HOW TO IDENTIFY MALINGERING ?
• Quality of voice: quality of voice is normal in malingers
• Cochleoauricular / Palpebral reflexes- present in these pts
This cause twitching of pinna/ contraction of palpebral muscles on exposure to
loud noise
• Gross discrepancy between PTA & Speech audiometry

149. TESTS FOR MALINGERING
1. Stengers test
2. Chimani Moose test
3. Teals test
4. Erhards test
5. Auditory Reflex threshold
6. Lombards test
7. Stethoscope test
8. Swinging story test
9. Doefler Stewart test
10. Delayed speech feedback test
11. Bekesy audiometry
12. Lengthened off time test

150. 1.STENGER’S TEST
• This test is performed to identify feigned hearing loss and malingering.
• This test is based on the auditory phenomenon known as “Stenger’s principle”.
This principle states that when two similar sounds are presented to both ears
only the louder of the two would be heard.
Patients usually are not aware of this phenomenon.
The test can be performed either with PTA or tuning forks.
When two similar tuning forks of same frequencies are made to vibrate and held
simultaneously in the acoustic axis of both ears only the louder fork will be
heard.

151. STENGER’S TEST
• The examiner stands behind the patient
• A tuning fork is struck & held 20 cm from the “good ear”-patient hears the
sound
• A fork is then removed & placed 5 cm from the “bad ear”- patient denies
hearing the sound
• Another tuning fork is kept 15 cm from the “good ear” without patient noticing
• If there is genuine hearing loss patient will be hearing in the good ear. This is
known as negative Stenger’s test.
• If malingerer- denies hearing at all. This is known as positive Stenger’s test

152. 2.CHIMANI MOOSE TEST
• Modification of weber test
• On placing vibrating tuning fork on the vertex – pt hears in good ear & not in
deaf ear
• Then meatus of good ear is occluded- if he is a malinger – denies hearing at all

153. 3. TEAL’S TEST
• Vibrating tuning fork is placed over the mastoid process of the so called deaf
ear- pt accepts to hear it
• Then pt is blindfolded & with a nonvibrating tuning fork on the mastoid process
pt claims to hear the sound

154. 4. ERHAD’S TEST
(LOUD VOICE TEST)
• In normal person when the ear is occluded with a finger, it dampens the sound
but can still be heard
• Malinger denies hearing it even with loudest sound

155. 5. AUDITORY REFLEX THRESHOLD
• Normal pt- stapedial reflex elicited at 70-100 db.
• In malinger stapedial reflex is present
6. LOMBARD’S TEST
• Lombards principle-one raises his/her voice when speaking in noisy environment
• Pt is allowed to read a book-noise introduced into the ear & gradually increased
till the patient raises his voice / stops reading.
• If no change- not a functional defect

156. 7. SWINGING STORY TEST
• To catch unilateral loss
• Story switches from one ear to both & to the other
• - one if you hear the full story
• -other if you only hear what is in good ear
8. DOEFLER STEWART TEST
• Persons with normal hearing raise their voice in presence of background noise
• Pt is asked to read a book & masking noise is fed to the deaf ear
• True deafness- masking noise has no effect on the voice

157. 9. DELAYED SPEECH FEEDBACK TEST
• Pt is asked to talk while you playback their own voice to them with a 200ms
delay
• Gradually raise the level-when they hear the voice, they will change their
speech
10. LENGTHENED OFF TIME TEST
• Similar to Bekesy audiometry
• Pulse tones have an off time of 800ms (in Bekesy - 200ms)
• Here pulse tracing falls than continuous tracing far more than Bekesy.

158. 11. STETHOSCOPE(COGGINS)TEST
• One ear piece of the stethoscope is closed with wax and used on the side of
deafness
• The chest piece is used to talk to the patient
• The malingerer gets confused and cannot tell whether he is hearing on right or
left side