3. INTRODUCTION
What is audiology ?
Sound is a physical stimulus that evoke sensation of hearing.
Audiometry is the measurement of hearing sensitivity.
4. SOUND
For sound to occur, must have a
SOURCE: Something has to be disturbed.
FORCE: Something has to disturb it.
MEDIUM (e.g. air): Something has to carry the disturbances.
When air molecules are
displaced, pressure waves
occur
6. FREQUENCY RANGE OF HEARING
SENSITIVITY
Humans: 20 Hz to 20 kHz.
Below 20 Hz, we feel a vibration rather than hear a sound.
Most people have very diminished sensitivity for frequencies > 8000-10, 000 Hz.
Bats (auditory specialists) : 2 kHz-100 kHz.
7. CASE 1
4 months old baby referred from secondary hospital as he failed OAE screening twice
Hx , normal SVD , no maternal infection , family hx : Have an uncle who's deaf and mute
Examination ears both intact TM
What hearing assessment will u do ?
8. BEHAVIOURAL OBSERVATION AUDIOMETRY (BOA)
Observing changes in behaviour in response to sounds.
For who? Very young babies (under 6 months corrected) or with similar functional age.
Calibrated (known frequency and intensity) noisemakers
Audiologist records sound level (from sound level meter), sound type & observed response-
observer determines whether response is present/absent
9. INFANTS 7 MONTHS - 3 YEARS
Aim: to detect hearing impairment greater than
20-30 dB HL
Typically use behavioural techiques
– Visual Reinforcement Orientation Audiometry (VROA) for 6-18 months
– Play audiometry
May incorporate objective testing if noncompliant or very difficult to test
10. CASE 2
20 years old female previously well came with 1 years hx of hearing loss , on and off ear discharge
O/E : Right ear moderate dry CP, left ear normal
Tunning fork test :
- weber lateralized to right
- Rennin +ve both ears
- What Audiological assessment would you order ?
11. PURE TONE AUDIOMETRY
Most common test
Threshold of audibility
Activation of auditory system
Energy formatted into neural
code
Air conduction assesses entire system
Bone conduction assesses cochlea onwards
12. HEARING LEVEL
Whats the difference between dB SPL & dB HL ?
dB SPL is a measure of sound pressure levels in air.
It’s measured in decibels (dB) relative to a pressure of 20 micro pascals.
dB SPL = 20log10(P1/P0) , P0 = 0.00002 pascals
Sound Event Sound Pressure (Pa) Sound Pressure Level (dB SPL)
30 meters from a military
aircraft at take-off
200
140 =20log10(200/.00
02)
Pneumatic chipping and
riveting (operator’s
position)
63 130
Boiler shop (maximum
levels)
20 120
Automatic punch press
(operator’s position)
6.3 110
Automatic lathe shop 2 100
Construction site—
pneumatic drilling
0.63 90
Kerbside of busy street 0.2 80
Loud radio (in average
domestic room)
0.063 70
Restaurant 0.02 60
Conversational speech at 1
meter
0.0063 50
Whispered conversation at
2 meters
0.002 40
Background noise in TV
and recording studios
0.0002 20
Normal hearing threshold 0.00002 0
16. CASE 3 :
70 years old male, DM , HTN, DLP came with long time hx of hearing loss in both ears , when
interviewing the patient he had difficulty hearing you & when u increase ur voice he replies “YOU DON’T
NEED TO SHOUT”
O/E : Bilateral intact TM,
What Audiological assessment is needed ??
PTA
What other tests can confirm diagnosis ?
17. TESTS FOR COCHLEAR PATHOLOGY
Recruitment is the hallmark of cochlear pathology
physical condition of the inner ear that leads to reduced tolerance of loudness. It commonly occurs in
individuals who suffer hearing loss due to cochlear damage. While low-magnitude sounds cannot be
heard in the affected ear, the perceived loudness increases over-proportionally with sound volume once
the auditory threshold has been overcome.
Tests of recruitment include
short increment sensitivity index (SISI)
alternate binaural loudness balance (ABLB)
18. SHORT INCREMENT SENSITIVITY INDEX (SISI)
measure of one’s ability to tell the difference between the loudness of sound.
test of a person’s ability to recognize 1 dB increases in intensity during a series of bursts of pure tones
presented 20 dB above the pure tone threshold for the test frequency.
patient with a cochlear disorder will be able to perceive the increments of 1 dB, whereas a patient with a
retro-cochlear disorder will not.
19. SISI
● The score is a percentage, which
expresses the number of 1 dB
increments the patient detected out
of the 20 in total, multiplied by 5:
• 70-100% correct = high (cochlear loss)
• 20-70% correct = inconclusive
• <20% = low (retrocochlear loss)
20. ALTERNATE BINAURAL LOUDNESS BALANCE (ABLB)
A test to detect perceived loudness differences between the ears and is useful in patients with unilateral
hearing loss
The test begins at 20 dB HL in the good ear. Then alternate the side and play
the same sound to the poorer ear. With a two-channel audiometer
Once you achieve equal loudness, increase the intensity in 20 dB steps until you reach either the
patient’s tolerance level or the maximum output of the audiometer.
23. CASE 4
40 years old male, post right cortical mastoidectomy presented with increase HL and tennitus on the right side
Since 2 months , with right side facial deviation and absent corneal reflex
O/E : right ear clear, intact TM , left side intact TM
Weber lateralize to left , rennin +ve bilaterally
PTA right sever to profound mixed HL , left normal HL
SDS : 40%
SISI :10%
ABLB : no recruitment
Tone Decay : 30%
Acoustic reflex : absent
Acoustic reflex Decay : positive reflex decay
24. TONE DECAY
The test involves looking at the patient’s response to the onset of a suprathreshold
sound and then their continuous response to this as it continues over time
A normal response should be maintained for a minute of stimulation. Should
a patient not be able to maintain this, the stimulus intensity is increased until a minute is achieved.
This is only increased up to a maximum 30dB suprathreshold.
25. A decay of between
15 and 20 decibels is indicative
of cochlear hearing loss.
A decay of more than 25 decibels is
indicative of damage to
he vestibulocochlear nerve
26. ACOUSTIC REFLEX DECAY
The acoustic reflex decay test measures whether a reflex contraction is
maintained or weakens during continuous stimulation (usually 10 seconds).
The test is usually conducted at 500 Hz and 1000 Hz, but not above these
frequencies as even normal ears can show decay at higher frequencies.
27. The test is performed by presenting a continuous
stimulus 10 dB above the ART
(acoustic reflex threshold at 500 Hz or
1000 Hz)for the given frequency
for a period of 10 seconds.
if the reflex response decreases to 50% of its original size within
the 10 seconds of testing,
the test would be positive for reflex decay.
28. GOING BACK TO HIS AUDIOLOGICAL ASSESSMENT
SDS : 40%
SISI :10%
ABLB : no recruitment
Tone Decay : 30%
Acoustic reflex : absent
Acoustic reflex Decay : positive reflex decay
Editor's Notes
AUDIOLOGY The study of sound and hearing
CYCLE: One complete period of compression
and rarefaction of a sound wave
VOR Uses operant conditioned
response and visual
reinforcement
Response typically head
turn. Eye turn also
possible
Complex visual
reinforcement usually
lighted puppet theatrecolour
movement and light
are important
dB SPL is often converted using dB weighting scales—dBA and dB HL—as these provide adjustments to account for the way in which humans perceive sound differently at different frequencies.
Audiologists create audiograms of a person’s hearing using the dB HL scale. Based on this, they can determine if a person’s hearing levels are better or worse than normal at each frequency.
Sensory -Loss of hair cells and supporting cells, flattening and atrophy of Organ of Corti -Abrupt steep highfrequency loss
Neural -Atrophy of spiral ganglion -Moderate slope at high frequency
Metabolic/ strial -Atrophy of stria vascularis -Flat sensory loss with earlier onset
Inner ear conductive/ mechanical - Stiffness of basilar membrane - Upward slope to high frequency
