2. • It is a subjective test
• It is a non invasive test
• It is a graphical recording of Hearing
Loss both quantitatively and
qualitatively.
• The audiometer is an electronic
device that generates pure tones.
The intensity of these tones and
increased/decreased in 5 dB steps.
3. PURE TONESOUND
Whenanobjectvibratesinfixedsingle
frequency,the soundwaveswill presenta
sinusoidalwavepattern knownassine-
wave.
Thesoundsensationproducedbysuch
a sine-waveiscalledasapuretone
sound.
Inpuretoneaudiometry,wetest the
hearingsensitivityofasubjectonlyfor
pure tonesounds.
10. So,in clinicalaudiometry,it isthe
relative threshold¬theabsolute
thresholdthatis measured.That
means,inaudiological measurements,
the intensity of soundis always
measured& expressedincomparison
to orin relationto anothersound
whichis idealnormalhearing
threshold.
11. DECIBEL & OTHER
RELATED TERMS
TheDecibelisthe unit by whichthe intensity
of the sound(or pressure exerted by a sound
stimulus)ismeasured.
Averageminimumwhichwillproducea
soundjustaudibletoanormalear:-
Inunitsofpressure0.00024dynes/sq.cm.
Inunitsofintensity1/100000000000000000
watts/sq.cm.
12. DECIBEL & OTHER
RELATED TERMS
BEL- A ratio expressed in logarithm(with
base 10)whichtellsushowmanytimesthe
sound we are measuring is stronger or
weakerthan areferencesound.(0-14)
BEL=logIO/IR
IO=intensityofthesound
IR=intensityofthereferencesound
13. deciBEL-onetenth of
BEL.
[DECIBEL(dB)=10logIO/IR]
SPL-signifiesthat apressurereference
has beenused(i.e.referencesoundhasa
pressurelevelof .00024dynes/sq.cm.)
Inactualpracticeitwasfoundthattheunitof
BEListoolargeandencompassesavery
hugeamountofsoundintensity.
14. DECIBEL & OTHER
RELATED TERMS
HL-Indifferentfrequenciesthe intensityor
the pressureof justaudiblesoundisslightly
different.Henceforstandardisation,different
amountof pressure(orintensity)havebeen
separatelycalculatedfor eachfrequency,
suchthat the minimum soundaudiblebya
normalsubjectin different frequenciesmay
bedesignatedas0dBHL,for that particular
frequency.
15. SL-Thisisinreferenceto the auditory
thresholdofaparticularsubject&
indicates howmuchsoundsensation
that particular subjectisactually
getting.
SL+handicap=HL.
DECIBEL & OTHER
RELATED TERMS
29. MASKING
Masking is doneby:
1.Whitenoise-consistsof soundof all
frequenciesfrom high to low.
2.Narrow bandnoise-moreeffectivefor
masking, consists of anarrow band of
noise 100-200 Hz above/below that
frequency.
3.Complex noise-low frequency
fundamental+multiples offrequencies up
to 4000Hz.Leastefficient for masking.
42. LIMITATIONS OF P.T.A.
4.IT DOES NOT IDENTIFYTHE NATUREOF
THE PATHOLOGY.
5.BONE CONDUCTION TEST DOES NOT
ASSESS THE TRUE SENSORINEURAL
RESERVE.
6.MANY SOURCES OF VARIANCES IN THE
TEST RESULTS THATARE NOT RELATED
TO HEARING.
43. RECRUITMENT
• It is a phenomenon of abnormal
appreciation of loud sounds, a loud
sound that is tolerable in normal
ear may grow to abnormal levels
of loudness in recruiting ear and
thus becomes intolerable.
• It is a feature of cochlear hearing
loss.
44. TESTS FOR RECRUITMENT
1) FOWLER’S ALTERNATE BINAURAL
LOUDNESS BALANCE TEST
• Done in case of unilateral hearing loss
• A tone of 1000 Hz is played alternatively to
the normal and affected ear.
• The intensity in the affected ear is
adjusted to match the loudness in normal
ear.
45. • The test begins at 20 dB above the
threshold and is repeated at every
10 dB rise until the loudness is
matched or limits of audiometer is
reached.
• The initial difference is maintained
throughout in normal hearing or
conductive hearing loss.
• Partial or complete or over
recruitment is seen in cochlear
lesions.
46. SHORT INCREMENT
SENSITIVITY INDEX TEST
• Due to the recruitment, patients of
cochlear lesions can distinguish
smaller changes in intensity of pure
tone better than patients of normal
hearing, conductive and nerve hearing
loss.
47. • Method:
A continuous tone is delivered 20 dB
above threshold and sustained for
about 2 minutes. At every 5 seconds,
the tone is increased by 1 dB.
Twenty such blips are delivered.
Patient is asked to indicate the blips
heard.
SISI score is presented in
percentage.
48. • Interpretations:
• Score less than 20% : Normal
hearing and conductive and
nerve hearing loss.
• Score more than 70%: Cochlear
hearing loss.
49. CARHART'S TONE DECAY TEST
This simple test is a measure of nerve
fatigue, which is a feature of retrocochlear
hearing loss.
Principle: A normal person can hear a tone
continuously for 60 seconds. In nerve fatigue,
patient stops hearing earlier.
50. • Method:
A tone of 4,000 Hz is delivered at 5 dB
above the patient's threshold for 60
seconds. When patient stops hearing,
intensity is increased each time by 5
dB.
• The procedure is continued till
patient hears the tone continuously
for 60 seconds or tone's upper limit
is reached.