1. The Basic Audiologic Evaluation
An introduction to audiometry
and impedance testing
Nicole J. Lanthier, MA, CCC-A
Clinical Audiologist, Reg. CASLPO

2. What is an Audiologist?
A professional holding a Master’s degree in Audiology, as well as a professional license or certification, who is educated in the areas of hearing measurement, hearing disorders, aural rehabilitation, amplification, & hearing conservation
Otolaryngologist ~= Opthalmologist
Audiologist ~= Optometrist
HearingAid Dispenser ~= Optician

3. Who Needs Audiologic Testing?
Infants, children, and adults
people known to be at risk through genetics, noise exposure (ongoing or episodic), oto-toxic drug exposure, aging, related health issues or trauma, those who are concerned about difficulties hearing (or friends/family are concerned about their hearing)
age = birth years

4. The Basic (Adult) Audiologic Evaluation
history, reason for referral
otoscopy
tympanometry
stapedial reflexes
pure tone audiometry
air and bone conduction; masking
speech testing (speech audiometry)

5. Tympanometry
tympanometry = an objective measure of eardrum compliance change as air pressure is varied in the external ear. An assessment of eardrum mobility. Also called dynamic compliance
tympanometric curve = pressure-compliance function

6. The Tympanogram Measured on an “impedance bridge”
A tympanogram will give an indication of the status of the middle ear, in terms of compliance
is the middle ear system “stiff” or “floppy”
what is the pressure in the middle ear space
is the eardrum intact

7. Tympanometric Norms for Compliance
typically ~ 0.3 cc cc WNL for adults; ~ cc for children
lower than this indicates high impedance, higher than this indicates high compliance
low compliance may indicate middle ear effusion or stiffening (otosclerosis)
high compliance could indicate TM scarring (flaccid monomeric areas), ossicular discontinuity

8. Tympanometric Norms - from Margolis &Heller, 1987
Compliance Vol. Width
(mmho or cc) (cc) (daPa)
ADULTS
(X = 0.8) (X=1.1) (X= 80)
CHILDREN (age years)
(X = 0.5) (X = 0.7) (X= 100)

9. Liden-Jerger Classification of Tympanometry
categorical classification of tympanograms
the most commonly used of classification systems; uses “alphabet” category names
normal tympanogram (normal compliance, pressure, morphology) is “Type A”

10. Type A with Subscript
Type Adeep (Ad) denotes a tympanogram with a peak and normal peak pressure, but increased compliance
e.g. peak pressure + 15 daPa, compliance 1.9cc
Type Ashallow (or As) denotes a tympanogram with a peak and normal peak pressure, but reduced compliance
e.g. peak pressure daPa, compliance 0.2cc

11. The Flat Tympanogram A flat or “type B” tympanogram can indicate
occlusive obstruction in the ear canal
look for smaller EAC volume; otoscopy
a TM which is not moving due to high middle ear impedance
look for normal EAC volume; otoscopy
a perforated TM
look for large volume; otoscopy

12. Type C Tympanogram - Negative Pressure
When peak pressure is lower than daPa this is a “Type C” tympanogram
indicates negative middle ear pressure; usually associated with eustacian tube dysfunction
compliance may be normal or reduced
“type C” can be concomitant with, a precursor to, or occur during resolution of middle ear effusion

13. Stapedial Reflexes (aka Acoustic Reflexes)
Loud acoustic stimulus will cause bilateral contraction (reflex) of stapedius muscles
measured on an “impedance bridge”
loud stimulus delivered to one ear, can measure reflex response on the ipsilateral or contralateral ear - measurement of both “ipsi” and “contra” gives best info

14. Acoustic Reflex Pathways
START: outer ear -> middle ear -> inner ear -> VIII nerve -> cochlear nucleus -> ipsilateral superior olivary complex
THEN
IPSI - ipsi facial nerve - > ipsi middle ear OR
CONTRA - contra superior olivary complex -> contra facial nerve -> contra middle ear

15. Stapedial Reflexes (aka Acoustic Reflexes)
use to detect non-organic hearing loss, investigate facial nerve function, investigate possible retrocochlear pathology
reflex can be also be absent due to middle ear dysfunction or severe hearing loss
look at reflex threshold norms compared to hearing levels

16. Reflex Decay
reflex decay test - present stimulus tone 10 dB higher than the patient’s reflex threshold for 10 seconds; 500 or 1000 Hz stimulus
measure the amplitude of the reflex for 10 seconds, if it is reduced 50% or more in this time period this is “reflex decay”
suggestive of retrocochlear pathology

17. Pure Tone Audiometry
Typically tested frequencies include 250 Hz Hz
humans can hear ~ 20 Hz Hz but this tested range of frequencies is the area of our most sensitive hearing and the frequencies most used in human speech
may include ultra high frequency testing (>8000 Hz) if monitoring high risk individuals (noise, cisplatin exposure etc.)

18. Pure Tone Audiometry
A calibrated audiometer is required to ensure that the presented sounds are the proper frequencies and intensities
calibrated earphones required to deliver the sounds
quiet testing area required to ensure detection of sounds is not masked

19. Earphones Earphones are sound transducers
Common styles or earphones include
supra-aural earphones
circumaural earphones
insert ear phones
bone conduction transducer/headband
speakers for sound-field presentation

20. Advantages of Insert Earphones
reduces chance of collapsing ear canals
best reduction of environmental noise
improved comfort
hygiene - usually disposable/cleanable tips
increased inter-aural attenuation
less need for masking
fewer masking dilemmas

21. Pure Tone Testing
Typically used protocol is a bracketing technique, beginning at 30 dBHL when thresholds unknown, or ~10 dB above known thresholds
if no response at 30 dB, go to 50 dB
bracket “10 down & 5 up”
e.g. response at 30, go to 20, response at 20, go to 10, no response at 10, go to 15; recheck 2-3x

22. Pure Tone Testing good idea to test better ear first
if there is an asymmetry in hearing of over 60 dB when using insert phones, or 40 dB using supra-aural phones, you may have problems with crossover and inadvertently stimulate the non-test ear
inter-aural attenuation ~60 dB w/ insert earphones, ~ 40 dB w/ supra-aural headphones

23. Crossover
E.g. - thresholds of 10 dB left and thresholds over 50 dB right will require masking w/ supra-aural headphones
e.g. thresholds of 10 dB left and thresholds over 70 dB right will require masking with insert earphones
if you do not mask, the sound will cross over via bone conduction

24. Crossover
To prevent getting responses from the non-test ear in these situations you must use masking noise
for pure tone testing use narrow band noise
for speech testing use speech weighted noise
remember crossover is by bone conduction even if stimulating via air conduction

25. Masking Various equations used - example here
For masking for air conduction
threshold of non-test ear, plus 15 dB
want to plateau 15 dB to ensure real threshold
ideally want 30 dB effective masking
remember that masking can also cross over, so you don’t want to overmask and elevate threshold of test ear- remember inter-aural attenuation

26. Masking Example - AC E.g. threshold left ear 10 dB, right 75 dB
begin with masking left 25 dB, present tone again right - if response obtained from right, increase masking 5 dB, if no response, increase presenting level to test ear by 5 dB
follow this until you are able to increase masking three times in non test ear with reliable responses from test ear

27. Bone Conduction
Bone conduction testing uses a vibrating sound generator held to the head to stimulate the inner ear ~ directly
“bypasses” outer and middle ear systems
usually test 250 or Hz with BC
usually use pure tone stimuli
typical placement on mastoid, (not touching pinna) can use forehead, teeth, nose

28. Bone Conduction
Use bone conduction when air conduction thresholds are elevated & want to differentiate b/w conductive and sensorineural hearing loss
conductive hearing loss - hearing loss due to pathology of outer or middle ear systems
AC thresholds elevated, BC thresholds WNL = conductive hearing loss

29. Air-Bone Gap
The difference b/w the AC and BC thresholds is called the “air-bone gap”, or the “conductive component”
e.g. AC threshold 45 dB, BC threshold 5 dB
air-bone gap, or “conductive component” 40dB
this indicates normal function of the inner ear and auditory CNS, problem OE or ME

30. Conductive Hearing Loss
Conductive hearing loss associated with
otitis media
otitis externa
TM perforation
ossicular discontinuity
otosclerosis
occluded ear canal/stenosed ear canal

31. Sensorineural Hearing Loss
if elevated AC and BC thresholds are the same (or very close, 5 dB, together) then the hearing loss is sensorineural
e.g.AC threshold 45 dB, BC threshold 45dB
OR AC = BC = 40
no air-bone gap, bypassing the OE and ME does not improve threshold, so hearing loss is sensorineural - due to IE/possibly retrocochlear

32. Sensorineural hearing loss
Called sensorineural since can be sensory or neural: typically sensory, due to IE/cochlea
popular but incorrect, “nerve deafness”
Sensorineural hearing loss associated with
noise exposure -retrocochlear pathology
aging -illness (e.g.meningitis)
ototoxic drugs -labyrinthitis

33. Mixed Hearing Loss
if there is an air-bone gap, but the BC thresholds are not WNL, then it is a mixed hearing loss
the degree of hearing loss is partly due to OE or ME and partly due to IE
e.g AC threshold 75 dB, BC 40 dB
air-bone gap 35 dB, BC threshold elevated out of normal range (>25 dB)

34. Mixed Hearing Loss MHL has a component of CHL and SNHL
Mixed hearing loss can be associated with:
otosclerosis
SNHL with otitis media,
SNHL with cerumen occlusion
SNHL with TM perforation
SNHL with overlay of etc. etc. etc.
post-surgical e.g. cholesteatoma removal

35. Speech Reception Threshold
SRT - lowest dB HL at which (closed set) speech can be understood
usually obtained by presenting descending levels of spondaic words (spondees) until only 50% score is obtained
use a list of familiarized words
spondee - two syllable word with equal emphasis on both syllables (e.g. hotdog)

36. Speech Reception Threshold
SRT is usually within ~ 6 dB of the pure tone average (PTA = average threshold using 500, 1000, and 2000 Hz)
if hearing loss is steeply sloping or has a “notch” SRT may be lower than PTA, closer to “best threshold”
quick reliability check - if SRT better than thresholds would indicate ? test validity

37. Speech Discrimination Testing
Present a list of published phonetically balanced words, usually words at a level allowing good audibility and comfort
usually ~ dB over PTA/SRT
NU-6, W-22
PBK for “kindergarten age” children
modify for special needs (board, write etc.)

38. Hearing “Sensitivity” vs. Hearing “Clarity”
speech discrimination testing gives an idea about the “clarity” of hearing
patients with identical audiograms (thresholds/sensitivity) may differ significantly in their functional auditory abilities depending on their speech discrimination abilities
unusually poor or asymmetric “discrim” can suggest retrocochlear pathology

39. Infants/Toddlers Below age of 6 months use ABR and OAEs
from age ~ months use visual reinforcement audiometry = VRA
usually done “in the soundfield”, child seated on parent’s lap between loudspeakers in a soundbooth; reinforcing toys hidden behind smoked glass on either side of child
condition child to turn to sound & reinforce

40. Young Children Age ~ 2 1/2 - 5 years use play audiometry
usually with earphones, condition child to respond to perceived sounds with a “play” response such as dropping a block in a bucket or putting a sticker in a book
can usually accomplish some speech testing
children/adults with “younger functional ages” can be tested in this manner as well

41. Amplification?
people with hearing loss affecting the frequency/intensity ranges of spoken language will often benefit from amplification (hearing aids or other varieties of amplification)
good speech discrimination allows better amplified performance
ensure appropriate hearing aid prescription

42. Other Audiologic Tests
ABR/BAER
ECOG
OAEs
CAP testing
tinnitus counselling

43. Re-Cap otoscopy tympanometry stapedial reflexes pure tone audiometry
air and bone conduction; masking
speech testing
other tests as needed to follow up

44. Abbrevations Used EAC = external ear canal WNL = within normal limits
TM = tympanic membrane (eardrum)
SRT = speech reception threshold
PTA = pure tone average
OE = outer ear
ME = middle ear

45. Abbrevations Used SNHL = sensorineural hearing loss
CHL = conductive hearing loss
MHL = mixed hearing loss
ABG = air bone gap
AC = air conduction
BC = bone conduction