1. DR.DHIMAN BHATTACHARYYA.
1ST YEAR PGT,MS(ENT)
IPGME&R & SSKMH,KOLKATA.

2. PURE TONE SOUND
 When an object vibrates in fixed single
frequency, the sound waves will present a
sinusoidal wave pattern known as sine-wave.
 The sound sensation produced by such a
sine-wave is called as a pure tone sound.
 In pure tone audiometry, we test the
hearing sensitivity of a subject only for pure
tone sounds.

4. AIMS OF PURE TONE AUDIOMETRY
 Whether the subject has any definite hearing
loss.
 Whether the hearing loss is
conductive/sensorineural/mixed type.
 In sensorineural deafness,wheather the
deafness is cochlear or retrocochlear.
 To note the degree of hearing dysfunction.

5. PURE TONE AUDIOMETER
 It is the electronic device used for creating pure
tone audiogram.
 It consists of an audio-oscillator which generates
pure tone sounds of different frequencies.
 Each tone can be separately amplified to a
maximum of 100 to 110 dB in most frequencies
except very low & very high frequencies.
 Audiometer is connected to standard & specified
bone conduction vibrator or earphones through
which sound is presented to subject’s ear.

7. THRESHOLD
 The International Standards Organisation has
defined hearing threshold as “the lowest sound
pressure level, at which under specified
conditions, a person gives a predetermined
percentage of correct responses on repeated
trails”.
 For clinical usage, this predetermined
percentage is 50%.
 In pure tone audiometry,we try to obtain
thresholds that compare the hearing sensitivity

8. THRESHOLD
 of a subject in decibels with a fixed ideal or
normal hearing level(0 dB).
 So, in clinical audiometry,it is the relative
threshold & not the absolute threshold that is
measured.That means, in audiological
measurements, the intensity of sound is
always measured & expressed in comparison
to or in relation to another sound which is
ideal normal hearing threshold.

9. DECIBEL & OTHER RELATED
TERMS
 The Decibel is the unit by which the intensity
of the sound(or pressure exerted by a sound
stimulus) is measured.
 Average minimum which will produce a
sound just audible to a normal ear:-
 In units of pressure 0.00024 dynes/sq.cm.
 In units of intensity 1/100000000000000000
watts/sq.cm.

10. DECIBEL & OTHER RELATED
TERMS
 BEL-A ratio expressed in logarithm(with base
10) which tells us how many times the sound
we are measuring is stronger or weaker than
a reference sound.(0-14)
[BEL=log IO/IR]
 DECIBEL-one tenth of BEL.
[DECIBEL(dB)=10 log IO/IR]
 SPL-signifies that a pressure reference has
been used(i.e. reference sound has a pressure
level of .00024 dynes/sq.cm.)

11. DECIBEL & OTHER RELATED
TERMS
 HL-In different frequencies the intensity or
the pressure of just audible sound is slightly
different. Hence for standardisation, different
amount of pressure(or intensity) have been
separately calculated for each frequency,
such that the minimum sound audible by a
normal subject in different frequencies may
be designated as 0 dB HL, for that particular
frequency.

12.  SL-This is in reference to the auditory
threshold of a particular subject & indicates
how much sound sensation that particular
subject is actually getting.
SL+handicap=HL.
DECIBEL & OTHER RELATED
TERMS

13. PROCEDURE OF P.T.A.
 AIR CONDUCTIONTESTS(conditions
required):-
 1.CALIBRATION OFTHE INSTRUMENT-
 ISO-1964 specification.
 6 monthly electronic calibration.
 Air conduction headphones-TDH39/TDH49.
 Insert ear-phones-ER-3A.
 Ear conduction head phone cushions-MX 41
AR.

17. PROCEDURE OF P.T.A.
 2.REASONABLY NOISELESS TEST
ENVIRONMENT-
 American standards Association(ANSI-53.1-
1991) table.
 ISO/DIS 8253 table.
 3.POSITION OF HEADPHONES.
 4.INSTRUCTIONTOTHE PATIENT.

18. PROCEDURE OF P.T.A.
 TECHNIQUE OF AIR CONDUCTION TESTS:-
 1.CONVENTIONAL/ HUGHSON-
WESTLAKE(5-up-10-down) technique.
 2.American Speech & Hearing
Association(ASHA) technique.
 3.British Society of Audiology/British
association of Otolaryngologists technique.
 4.ISO/DIS 8253 technique.

20. PROCEDURE OF P.T.A.
 BONE CONDUCTIONTESTS(conditions
required):-
 1.Calibration of the instrument-Radio ear B71.
 2.Reasonably noiseless test environment.
 3.Placement of bone conduction vibrator-
 a)Mastoid placement-
 Superior in respect of sensitivity by 10-15 dB.
 The bone conduction vibrator is placed over the
mastoid bone attached to a spring metal
headband.The pressure on mastoid is given as
500 gm/sq.cm.

21. PROCEDURE OF P.T.A.
 Area over which the person can hear the sound
loudest is placed.
 The testing ear is kept uncovered.The other ear
is kept covered for masking.
 The bone conduction vibrator must not touch
the pinna or the earphone.
 b)Frontal placement-Superior in respect of
consistency because of less variation of amount
of tissue between bone conduction vibrator &
the earphone.
 TECHNIQUES OF BONE CONDUCTION.

22. MASKING
 In pure tone audiometry, the clinician must
ascertain the exact hearing threshold by air &
bone conduction for the different frequencies
for each of the two ears separately &
individually.This can not be taken lightly &
needs to be over-emphasised.
 Contralateral masking means introducing a
noise in non-test ear, such that the non-test
ear is acoustically blocked & can not
participate in the hearing test.

23. MASKING
 When to mask:-
 Interaural attenuation(40-45 dB HL for air
conduction).
 Hazard of cross hearing is much more in bone
conduction than in air conduction test.
 Chance of cross-hearing is AC(test ear)-
BC(non-test ear)>IA.
 For bone conduction, the Interaural
attenuation may be 0 dBHL.

24. MASKING
 How much to mask-neither undermask,nor
overmask.
 Minimum masking level:
 (AC)Air conduction threshold in the test ear-
45+(Air conduction threshold in the masked
ear-Bone conduction threshold in the masked
ear).
 Maximum masking level:
 Bone conduction threshold for the test
ear+45.

25. MASKING
 Masking is done by:
 1.White noise-consists of sound of all
frequencies from high to low.
 2.Narrow band noise-more effective for
masking, consists of a narrow band of
noise 100-200 Hz above/below that
frequency.
 3.Complex noise-low frequency
fundamental+multiples of frequencies up
to 4000 Hz. Least efficient for masking.

26.  A) QUANTITATIVE INFORMATION-
 1.What is the AC threshold?
 2.What is the BC threshold?
 3.What is the A-B gap?
 4.Wheather masking has been done or not?
 5.Does it match with clinical findings and
tuning fork tests?
 B)QUALITATIVE INFORMATION.
INTERPRETETION OF P.T.A.

27. PTA OF CONDUCTIVE DEAFNESS

28. PTA OF SENSORINEURAL DEAFNESS

29. PTA OF MIXED DEAFNESS

30. CONDUCTIVE DEAFNESS
AC threshold>30dB.
BC threshold<20 dB.
A-B gap>25 dB.

31. SENSORINEURAL DEAFNESS
AC threshold>30 dB.
BC threshold>20 dB.
A-B gap<20 dB.

32. MIXED DEAFNESS
AC threshold>45 dB.
BC threshold>20 dB.
A-B gap>20 dB.

33. CONDUCTIVE DEAFNESS IN OSSICULAR
DISCONTINUITY

34. CARHART’S NOTCH(OTOSCLEROSIS)

35. STRIAL PRESBYACUSIS(S.N.D.)

36. S.N.D. D/T ACOUSTIC TRAUMA

37. LIMITATIONS OF P.T.A.
 1.AUDIOGRAMSAREVERY OFTEN
INACCURATE.
 a)Improper technique- masking, placement.
 b)Improper test condition-RNTE.
 c)Improper test instrument- calibration.
 d)Improper examiner.
 2.A SUBJECTIVE &TIME-CONSUMINGTEST.
 3.IT DOES NOT ASSESSALL FEATURESOF
HEARING.

38. LIMITATIONS OF P.T.A.
 4.IT DOES NOT IDENTIFYTHE NATURE OF
THE PATHOLOGY.
 5.BONE CONDUCTIONTEST DOES NOT
ASSESSTHETRUE SENSORINEURAL
RESERVE.
 6.MANY SOURCES OFVARIANCES INTHE
TEST RESULTSTHATARE NOT RELATEDTO
HEARING.

39. HAVE A GOOD DAY