1. Audiometry
Dr. Vishal Sharma

2. Pure Tone Audiometer

3. Pure Tone Audiometry
5 up, 10 down technique used with single frequency tones to find hearing threshold.
2 correct responses out of 3 is acceptable.
Air conduction measured for 1K, 2K, 4K, 8K, 500, 250 & 125 Hz via head phone.
Bone conduction measured for 1K, 2K, 4K, 500 & 250 Hz via bone vibrator. Masking of other ear.
Normal hearing for AC & BC is at 0 dB.

4. Symbols used in audiogram

5. Normal Audiogram

6. Pure Tone Average
Calculated by taking arithmetic mean of air conduction
thresholds at 500, 1000 & 2000 Hz (speech frequencies)

7. Classification of Deafness: Goodmann & Clark
P.T.A. (dB)
Type
0 - 15
Normal
56 – 70
Moderate Severe
16 – 25
Minimal
71 – 91
Severe
26 – 40
Mild
> 91
Profound
41 – 55
Moderate

10. Conductive deafness

11. Sensori-neural deafness

12. Mixed deafness

13. Diagnosis of type of deafness
Air Conduction
Bone Conduction
Air bone gap
Conductive
Worsened
Normal
Present
Sensori-neural
Absent
Mixed

14. Low frequency conductive HL
Otitis media with effusion

15. Carhart’s notch (otosclerosis)

16. High frequency SNHL
Presbyacusis, ototoxicity, acoustic neuroma

17. Low frequency SNHL (Meniere)

18. Deafness in Meniere’s disease

19. Acoustic dip (Noise deafness)

20. Uses of pure tone audiogram
1. To find type of hearing loss
2. To find degree of hearing loss
3. For prescription of hearing aid
4. Predict hearing improvement after ear surgery
5. To predict speech reception threshold
6. A record for future medico-legal reference

21. Speech Audiometry
Speech Reception Threshold (S.R.T.): Minimum intensity at which 50% of spondee (disyllable with equal stress) words are correctly identified.
S.R.T. is normally within 10 dB of Pure Tone Average.
Speech Discrimination Score (S.D.S.): Percentage of phonetically balanced (single syllable) words correctly identified at 40 dB above S.R.T.

22. Speech Audiometry PB max Score: Maximum SDS at any intensity.
Uses of Speech Audiometry
Differ b/w cochlear & retro-cochlear lesions.
Volume of hearing aid fixed at PB max score
In functional deafness: SRT > + 10 dB of pure tone average.

23. Speech Audiogram

24. Speech Discrimination
Hearing loss
Speech understanding
0 – 25 dB
No difficulty with faint speech
26 – 40 dB
Difficulty with faint speech only
41 – 55 dB
Difficulty with faint + normal speech
56 – 70 dB
Difficulty even with loud speech
71 – 91 dB
Only understands amplified speech
> 91 dB
Can’t understand amplified speech

25. Special Audiological Tests

26. Tests for Recruitment Recruitment is abnormal growth in perception
of sound intensity. Tests of recruitment are
done to diagnose a cochlear pathology.
Tests used are:
1. Short Increment Sensitivity Index (SISI) Test
2. Alternate Binaural Loudness Balance (ABLB) Test

27. S.I.S.I. Test (Jerger, 1959)
Continuous tone given 20 dB above hearing threshold & sustained for 2 min.
Every 5 sec, tone intensity increased by 1 db and 20 such blips are given.
SISI score = % of blips heard.
% in cochlear deafness
0-20 % in conductive & nerve deafness

28. A.B.L.B. Test (Fowler, 1936)
Pure tone is presented alternately to deaf &
normal ear. Intensity heard in normal ear is
adjusted to match with deaf ear. Test started 20
dB above threshold in normal ear & repeated with
10 dB raises till loudness is matched in both ears.
Initial difference is maintained, decreased &
increased in conductive, cochlear & retro-
cochlear lesions respectively.

29. Laddergram in A.B.L.B. test

30. Threshold Tone Decay Test
Olsen & Noffsinger (1974)
Detects abnormal auditory adaptation due to nerve fatigue caused by a retro-cochlear lesion.
Pure tone presented 20 dB above hearing threshold, continuously for 1 min. If pt stops hearing earlier, intensity ed by 5 dB & restart.
Test continued till pt hears tone continuously
for 1 min or intensity increment (decay) > 25 dB

31. Interpretation Tone Decay Pathology dB Type 0-5 Absent Normal 10-15
Mild
Cochlear
20-25
Moderate
> 25
Severe
Retro-Cochlear

32. Impedance Audiometry

33. Impedance Audiometer Probe
A = oscillator (220 Hz). B = air pump C = microphone to pick up reflected sound

34. Impedance Audiometry 1. Tympanometry
2. Acoustic reflex (Stapedial reflex)
Principles of Tympanometry
a. Less compliant T.M. reflects more sound.
b. Maximum compliance of T.M. denotes equal pressure in E.A.C. & middle ear.

35. Tympanogram parameters
Adult
Child
Compliance
0.5 – 1.75 ml
Middle ear pressure
+ 100 to Deca Pascal
+ 60 to Deca Pascal
External
Auditory Canal volume
1.0 – 3.0 ml
0.5 – 2.0 ml

36. Tympanogram Types (Jerger)

37. Types of Tympanogram Seen in Type Pressure Compliance A As Ad B C
Normal
Normal ME As
Decreased
Otosclerosis Ad
Increased
Ossicular discontinuity B
Nil (flat curve)
Fluid in ME, TM perforation C
Negative
ET obstruction

38. Type A

39. Type As

40. Type Ad

41. Type B (fluid in middle ear)
EAC volume = 1.8 ml

42. Type B (T.M. perforation, grommet)
EAC volume = 3.2 ml

43. Type B (E.A.C. obstruction)
EAC volume = 0.4 ml

44. Type C

45. Acoustic Reflex
Loud sound > 70 dB above hearing threshold, causes B/L contraction of stapedius muscles, detected by tympanometry as se in compliance.

46. Uses of Acoustic Reflex
1. Objective hearing test in infants & malingerers
2. Presence of reflex at <60 dB above threshold is seen in cochlear lesion due to recruitment
3. Reflex amplitude decay of > 50 % within 10 sec is seen in retro-cochlear lesion
4. Absence of reflex seen in facial nerve lesion
proximal to stapedius nv & in severe deafness
5. I/L reflex present, C/L absent in brainstem lesion

47. B/L reflexes present

48. Stapedial reflex absent

49. Acoustic Reflex Decay

50. Electro-cochleography
Measures auditory stimulus related cochlear
potentials by placing an electrode within external
auditory canal / on tympanic membrane / trans-
tympanic placement on round window.
3 major components:
a. Cochlear microphonics: from outer hair cells
b. Summating potential: from inner hair cells
c. Compound Action potential: from auditory nerve

51. Trans-tympanic electrode

52. Electro-cochleography findings in Meniere’s disease
Summation potential : compound action potential ratio > 30 %
Widened waveform
Distorted cochlear microphonics

53. SP – AP Waveform

54. Cochlear Microphonics
SP/AP > 30 %
Normal
Distorted CM

55. Otoacoustic Emission (Kemp echoes)
Sounds generated within normal cochlea due to
activities of outer hair cells.
Types: 1. Spontaneous: absent in > 25 dB HL
2. Evoked: transient; distortion product
Applications: Objective & non-invasive test for:
Hearing screening in neonates
Evaluation of non-organic hearing loss

56. Otoacoustic Emissions (OAE)
Spontaneous OAE: Sounds emitted without stimulus
Transient evoked OAE: Sounds emitted in response to click stimulus of very short duration
Distortion product OAE: Sounds emitted in response to 2 simultaneous tones of different frequencies & intensities
Sustained-frequency OAE: Sounds emitted in response to a continuous tone

57. Normal Spontaneous OAE

58. Normal Transient evoked OAE

59. Normal Transient evoked OAE

60. Normal Distortion Product OAE

61. Early detection of N.I.H.L.

62. Early stage N.I.H.L.

63. Advanced stage N.I.H.L.

64. Malingering of N.I.H.L.

65. Auditory Evoked Potentials

66. Auditory Evoked Potentials
Auditory Brainstem Response: ms post stimulus; originates in 8th cranial nerve (waves I & II) up to lateral lemniscus & inferior colliculus (wave V)
Middle Latency Response (MLR): ms post stimulus; arises in upper brainstem & auditory cortex
Slow Cortical Response: ms post stimulus; originating in auditory cortex

67. Brainstem Evoked Response Audiometry (B.E.R.A.)
Auditory evoked neuro-electric potentials
recorded within 10 msec from scalp electrodes.
Applications: Objective test
1. Hearing threshold for uncooperative pt / malingerer
2. Hearing threshold in sleeping / sedated / comatose
3. Diagnosis of retro-cochlear pathology
4. Diagnosis of C.N.S. maturity in newborns
5. Intra-op monitoring of auditory function

68. Hearing test of comatose pt

69. Anatomy of B.E.R.A. waves

70. B.E.R.A. waves

71. Normal inter-wave latencies

73. Cortical Evoked Response Audiometry (CERA) or P1-N1-P2 response
good frequency specificity over speech frequency range ( Hz)
recorded from higher auditory level than BERA, so less subject to organic neurologic disorders
CERA must be done to evaluate accurate hearing threshold in pt with flat audiogram & hearing threshold of > 25 dB at 500 Hz

74. Multiple Auditory Steady-state Evoked Response audiometry
Are responses to rapid stimuli where brain response to one stimulus overlaps with responses to other stimuli
Slow rate responses (<20 Hz) arise in cortex & faster rate responses (>70 Hz) originate in brainstem 
Gives rapid, frequency specific & objective hearing assessment by giving 4 continuous tones to each ear

75. Multiple Auditory Steady-state Evoked Response audiometry

76. Audio Test Cochlear Retro-cochlear
Speech Audiometry
S.D.S. = %
< 40 %, Roll over phenomenon
S.I.S.I.
Positive (> 70 %)
Negative
A.B.L.B. laddergram
Converging
Diverging
Tone decay
Negative (< 25dB)
Positive (> 25dB)
Stapedial reflex
Reflex at < 60 db SL; Decay absent
Reflex at > 70 db SL; Decay present
B.E.R.A. (Wave V latency)
< 4.2 msec
> 4.2 msec

77. Thank You