Pure tune audiometry Air- and bone-conduction thresholds Recruitment Carhart’s tone decay test Bekesy audiometry Speech audiometry Impendence audiometry Tympanometry Acoustic reflex Acoustic reflex decay test

1. Audiology
 Dr. Amro Yousef Alamleh

2. Audiometric tests
1. Pure tune audiometry
 Air- and bone-conduction thresholds
 Recruitment
 Carhart’s tone decay test
2. Bekesy audiometry
3. Speech audiometry
4. Impendence audiometry
 Tympanometry
 Acoustic reflex
 Acoustic reflex decay test

3. Pure Tone Audiometry
 It is non-invasive subjective test
 It is a graphic recording of hearing level both quantitatively and
qualitatively.
 An audiometer is on electronic device that generates pure tones. The
intensity of these tones are either increased or decreased in 5 dB
steps.
 The graph on which these thresholds are charted is called
audiogram.

5.  The AC thresholds are measured usually for tones of 250, 500, 1,000, 2,000,
4,000 and 8,000 Hz by using headphones or insert earphones
 The BC thresholds are measured usually for 250, 500, 1,000, 2,000 and 4,000
Hz by using vibrator (bone oscillator) on mastoid process.
 The speech frequencies range from 500–2,000 Hz4.
 Pure tone average: The pure tone average is an average of the AC thresholds
at 500, 1,000, and 2,000 Hz speech frequencies.

8. Method
 Audiometry is done in a soundproof room (ideal) or a quite room.
 First AC and then BC is recorded separately for each ear.
 Audiometry legend
 For right ear  red color pencils are used
 For left ear  blue color pencils are used
 For AC  continuous line
 For BC interrupted (broken) line is used for recording.

12. Masking
 Crossover occurs when sound signal to test ear strong enough to
vibrate skull and travel to nontest ear.
 Interaural attenuation is reduction in sound energy from one side
of skull to other.
 Interaural attenuation depending on
1. Frequency
2. Patient characteristics  From patient to patient (Skull
thickness)
3. Transducer used (headphones, insert earphones, vibrator)

13. Interaural attenuation
 Interaural attenuation for air conduction
 with headphones is 40 to 65 dB
 with insert earphones is over 70 dB (70-90 dB)
 Insert earphones allow much higher interaural attenuation and, thus, there is much
less chance of crossover. Interaural attenuation may be 70 to 90 dB, which
 It often eliminates the need for masking during air conduction testing.
 IA attenuation for bone conduction 0 to 10 dB.
 Crossover in air conduction can occur as low as 40 dB HL and in
bone conduction as low as 0 dB HL.

16.  Two rules of when to mask (pure tone or speech
audiometry):
 Air conduction:
 Mask the nontest ear whenever the air conduction level to the test
ear exceeds the bone conduction level of the nontest ear by 40 dB
or more for circumaural earphones, 70 dB or more for insert
earphones.
 When difference between the AC of two ears is 40 dB or more, the
better ear is masked.
 Bone conduction: Mask the nontest ear whenever there is
an air–bone gap greater than 10 dB in the test ear.

18. Pure tone testing yields one of several
audiogram types:
 1. Normal hearing: All air conduction thresholds in both ears are within
normal limits (≤ 25 dB HL).
 2. Conductive hearing loss: Hearing loss measured only by air conduction,
with normal bone conduction thresholds, indicating outer or middle ear
pathology.
 3. Sensorineural hearing loss: Hearing loss by air and by bone conduction of
similar degree, indicating pathology of the cochlea (sensory) or of the nerve
(neural).
 4. Mixed hearing loss: Hearing loss by both air and bone conduction but air
conduction hearing is worse than bone conduction, indicating a combination
of conductive pathology overlaid on sensorineural pathology.

19. Audiometric configuration
 Audiometric configuration of the loss is important information. The audiogram
may be:
1. Flat
2. Rising
3. Sloping
4. Falling
5. Notched
6. Saucer-shaped
 Thus, pure tone air and bone conduction threshold testing provides a good profile
of an
 individual’s hearing. However, pure tone results should be interpreted in
conjunction with
 speech audiometry, tympanometry, and acoustic reflexes.

24. Recruitment
 In this phenomenon of abnormal appreciation of loud sounds, a loud sound
which is tolerable in normal ear may grow to abnormal levels of loudness in
the recruiting ear and thus becomes intolerable.
 Recruitment is a feature of cochlear hearing loss (Meniere’s disease,
presbycusis).
 It is absent in
 Persons with normal hearing
 CHL (external and middle ear diseases)
 Nerve hearing loss (acoustic neuroma).
 The common tests for recruitment are
 Fowler’s alternate binaural loudness balance test (ABLB)
 Short increment sensitivity index (SISI) test.

25. Short increment sensitivity index (SISI) test
 A continuous tone is delivered 20 dB above the threshold
 Frequency 1000 Hz
 Sustained for about 2 minutes.
 At every 5 seconds the tone is increased by 1dB.
 20 such blips are delivered.
 Patient is asked to indicate the blips heard.
 SISI score is presented in percentage.
 Interpretations
 Score less than 20%: Normal hearing and conductive and nerve hearing loss.
 Score more than 70%: Cochlear hearing loss.

26. Carhart’s Tone Decay Test
 This simple test is a measure of nerve fatigue, which is a feature retro-
cochlear hearing loss.
 Principle:
 A normal person can hear a tone continuously for 60 seconds.
 In nerve fatigue, patient stops hearing earlier.
 A tone of 4,000 Hz is delivered a t 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.
 Interpretation: A tone decay of more than 25 dB is diagnostic of a
retrocochlear hearing loss.

27. Békésy Audiometry
 Auditory phenomenon: auditory adaptation or fatigue
 Procedure
 Using a Bekesy audiometer, patient plots own threshold by pressing a
button when a tone is just heard and releasing it when the tone is no longer
heard.
 Bekesy audiometer automatically decreases and increases intensity
according to patient’s button responses while it sweeps across frequency.
 Two tracings made, first for an interrupted (I) tone and then for a
continuous (C) tone

28.  Interpretation
 Type I: I and C tracings overlap; normal
 Type II: C drops 10 to 20 dB below I above 1000 Hz; cochlear site
 Type III: C drops steadily below I, beginning in low frequencies, by as
much as 50 dB or to audiometer’s limit; VIII nerve site
 Type IV: C drops below I tracing, beginning in low frequencies, by about
30 dB but courses parallel with I; VIII nerve site
 Type V: C is above I tracing, suggestive of pseudohypoacusis

29.  Sensitivity for cochlear site good (93%) but sensitivity for VIII nerve
poor (49%).
 Tone Decay Test (TDT) takes less time and is superior for assessing
auditory fatigue; acoustic reflex decay even better.
 Bekesy test equipment is no longer available at most audiology clinics.

30. Type I
 “C” tracing overlaps the
“I” tracing.
 Both about 10 dB wide.
 Occurs in normal ears
and in disorders of
middle ears.

31. Type II
 “C” tracing overlaps the “I” tracing
at low frequencies.
 Somewhere between 500 and 1000,
“C” tracing drops to 10-15 dB below
“I” tracing and runs parallel to it all
the way out to the high frequency
end.
 This type occurs in some cochlear
disorders.

32. Type III
 “C” tracing drops dramatically
below “I” tracing, sometimes as
much as 40-50 dB.
 It continues down to the intensity
limit of the equipment.
 The break can occur at almost
any point in the frequency range.
 It occurs in 8th nerve disorders.

33. Type IV
 “C” tracing runs below “I”
tracing at all frequencies.
 No overlap at low
frequencies.
 This type occurs in some
8th nerve disorders.

34. SPEECH AUDIOMETRY
 Speech audiometry is the measurement of patient’s ability to hear
and understand the speech.
 The three parameters studied are:
1. Speech detection threshold (SDT)
2. Speech reception (recognition) threshold (SRT)
3. Speech discrimination score (SDS)

35. Speech Reception Threshold (SRT)
 SRT is the minimum intensity (lowest level in dB) at which 50% of
spondee words are repeated correctly.
 Spondee words are two-syllable words with equal stress on each
syllable such as oatmeal, popcorn, shipwreck, blacknight, blackboard,
football, eardrum, sunset, and daydream.
 Method: A set of spondee words is delivered to each ear of the patient.
The word lists are delivered through the headphone of an audiometer.
The intensity of spondee words are changed in 5 dB steps till half
of them are correctly heard.

36. SRT
 Interpretations:
 The SRT is normally within the range of 10 dB of the pure tone average
(PTA, the average of air conduction thresholds at three speech frequencies
(500, 1,000 and 2,000 Hz)).
 In cases of hearing loss, SRT is more than 10 dB better than pure tone
average.
 The SDT and PTA are typically 9 dB lower than SRT.

37. Speech Discrimination Score or Speech
Recognition Score (SDS)
 SDS is percentage of phonetically balanced (PB) words that patient repeats correctly.
 Phonetically balanced (PB) words (Phonemes) are single-syllable words such as fish,
dish, pin, sin.
 Method: The PB words are delivered through the headphone to each ear at an intensity 30–
40 dB above the SRT. A list of 50 PB words is presented and the number correctly heard is
multiplied by 2.
 Interpretation:
 Normal hearing: SD score of 95–100%
 Conductive hearing loss: SD score 90–100% but at higher intensities.
 Sensorineural hearing loss: SD score is less. Nerve hearing loss has very poor score
in comparison of cochlear hearing loss.

38.  Interpretation is as follows:
 90% to 100% correct normal
 76% to 88% correct slight difficulty
 60% to 74% correct moderate difficulty
 40% to 58% correct poor
 40% correct very poor

40. Test Cochlear HL Retro-cochlear HL
Recruitment Present Absent
Tone decay test Less than 25 dB More than 25 dB
Békésy Audiometry Type II Type III, IV
(SISI) test More than 70% Less than 20%
SDS Difficulty Poor, very poor
Acoustic reflex decay
test
Negative Positive

41. Impedance/Immittance Measures
Impedance audiometry
 Measures of middle ear function can be based on
 Impedance is the amount of energy rejected by middle ear
 Admittance is the amount of energy accepted by the middle ear.
 Impedance and admittance are opposite sides of the same phenomenon and yield
the same information. The term “immittance” was coined to accommodate both
approaches.
 The tests performed on an immittance/impedance meter in a routine test battery are
1. Tympanometry
2. Acoustic (stapedial) reflexes

42. Immittance analyzer
 Immittance analyzer to assess middle ear function and acoustic reflex
 The immittance analyzer usually has the following components:
1. Probe tip (For tympanometry) which has three channels with following
functions.
 Deliver a tone of 220 Hz
 A microphone, which picks up the reflected sound
 Pressure control (to increase or decrease manually the pressure in the ear canal
during tympanometry)
2. Frequency selector (for acoustic reflex and reflex decay testing)
3. Intensity selector (for acoustic reflex and reflex decay testing)
4. Earphone (for stimulating the contralateral ear reflex)

45.  Tympanometry is an objective test that measures the mobility (compliance) of the
middle ear at the tympanic membrane as a function of applied air pressure in the
external ear canal.
 Compliance is expressed as acoustic admittance in millimho (mMho) or as
admittance of equivalent volume of ear in cm3 of mL.
 Pressure is expressed in dekapascals (daPa)
 Tympanometry results are represented by air pressure/compliance graphs, which
are called tympanograms that are diagnostic of certain middle ear pathologies.

46.  When a sound hits tympanic membrane, some of the sound energy is absorbed while
the rest is reflected. A stiffer tympanic membrane reflects more of sound energy
than a compliant one. The reflected sound energy is measured to find the
compliance or stiffness of the tympano-ossicular system
 As pressure changes, the point of maximum compliance of the middle ear is
identified as a peak on the tympanogram.
 The point of maximum compliance indicates the pressure at which the eardrum is
most mobile and occurs when the pressure in the external ear canal equals the
pressure in the middle ear. The peak air pressure of tympanogram is equal to middle
ear pressure.

47. Normal values
 Ear canal Volume :
 Adults  0.6 – 2 mL
 Childern  0.5 – 1 mL
 Compliance : 0.3 – 1.5 cm3
 Pressure : – 100 to + 100 daPa

48. Types of tympanograms
 There are five types of tympanograms.
1. Type A
2. Type B
3. Type C (C1 and C2)
4. Type As
5. Type Ad

52. Acoustic/stapedial Reflex
 Acoustic reflex is contraction of the stapedial muscles elicited by the
presentation of an acoustically loud sound (70–100 dB above the pure tone
threshold of hearing) (median = 85 dB).
 If pure tone thresholds were at 10dB HL, you would expect ipsilateral ARTs
between 80 – 90dBHL and contralateral ARTs between 85-95dBHL as an
approximation).
 When either ear is presented with a loud sound, the stapedius muscles on both
sides contract. Contraction of the stapedius muscle tilts the anterior stapes away
from the oval window and stiffens the ossicular chain. This results in increased
impedance which is detected by tympanometry as a small decrease in
compliance by an ear canal probe.

54.  Tone is delivered to one ear and the reflex is detected from the
same and the contralateral ear.
 Acoustic reflex neural pathways
 Though the majority of neurons run through ipsilateral pathway,
some crosses the brainstem to continue to the opposite cochlear
nucleus. The pathway begins at cochlea and proceeds through CN
VIII, cochlear nucleus, trapezoid body, superior olivary complex,
and motor facial nucleus to the stapedial muscle.

55.  Ipsilateral pathway: The loud sound travels through the outer,
middle and inner ear, then along the vestibulocochlear nerve
(CNVIII)  ipsilateral ventral cochlear nucleus the superior
olivary complex  the CNVII nuclei  CNVII  contraction of
the stapedius muscle.
 Contralateral pathway: In the contralateral reflex pathway, the
loud sound travels through the outer, middle and inner ear, then
along the CNVIII to the brainstem arriving at the cochlear
nucleus. From here the signal travels to the other superior olivary
complex and the other CNVII nuclei. The signal is then sent
down the CNVII causing contraction of the stapedius muscle

56. 1. Normal hearing
2. Mild to Moderate cochlear hearing loss

57. 1. Mild conductive hearing loss in the left ear
2. Facial nerve lesion in the left ear

58. 1. Severe to Profound cochlear hearing loss in the left ear
2. Retrocochlear lesion in left ear

59. 1. Severe conductive hearing loss in left side
2. Intra-axial brainstem disorder in left side

60. Cochlear hearing loss
 In ears with a cochlear hearing loss, it is possible for the acoustic
reflex to be elicited at sensation levels of less than 60 dB.
 The sensation level is the difference between the ART and the
hearing threshold.
 For example, if the hearing threshold at 1 kHz is 50 dB HL and the
ART is 90 dB HL, the sensation level is 40 dB.
 A sensation level of less than 60 dB is a positive Metz test
 This indicates a cochlear site of lesion (sensorineural loss) due to the
loudness recruitment phenomenon.

62. Acoustic reflex decay test
 It can be useful in detecting/confirming a retrocochlear pathology.
 But the test may be useful when the audiogram and case history are
normal, but reflex results show a retrocochlear pattern.
 It 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.

63.  The test is performed by presenting a continuous stimulus 10 dB above the
ART (acoustic reflex threshold) for the given frequency for a period of 10
seconds.
 The size of the reflex response will either stay the same or decrease during the
10-second period.
 Acoustic reflex decay test
 Negative
 If the reflex dose not decrease
 If it decreases by less than 50 % of its original size
 Positive, if it decreases to 50 % of its original size within 10 seconds of
testing