1. LET’S REVIEW…
HIS 230

2. Basic Hearing Evaluation
 Audiogram
 Puretone audiometry
 Air-conduction (AC) and bone-conduction (BC) testing
 Speech audiometry
 Speech reception threshold (SRT)
 This may also be called speech recognition threshold
 Word recognition score (WRS)
 This may also be called speech discrimination score
 The goal is to determine
 How well you hear
 How clearly you hear speech
 If there is a medical reason for hearing loss
 If there is a need for some sort of intervention

3. Puretone Audiometry
 Recall that human ears have an audible
bandwidth (frequency range) of 20 to 20,000
Hz
 In audiometric testing, the stimuli are
puretones from 250 to 8000 Hz.
 Why?
 because human speech falls within these frequencies
 Most commonly octave bands at 250, 500, 1000,
2000, 4000, and 8000 Hz are tested
 The interoctave frequencies of 3000 and 6000 Hz
are also commonly tested in adults

4. Puretone Audiometry
 Air-conduction testing
 Performed with headphones or insert earphones
 Takes into account the entire auditory pathway
 Outer ear, middle ear, inner ear, nerve, brain
 Bone-conduction testing
 Performed with a bone-conduction oscillator
placed on either mastoid bone (most common) or
the forehead
 Directly stimulates the inner ear and nerve
 Bypasses the outer and middle ear

5. Puretone Audiometry
 Threshold is the softest sound that a listener can hear
50% of the time
 A bracketing technique is used to establish threshold.
 Remember…down 10, up 5.
 If the patient responds, reduce the stimulus intensity by 10
dB. If no response, increase intensity using 5 dB steps.
Repeat this procedure until you find threshold.
 The patient’s thresholds are recorded on the
audiogram.
 I prefer to start testing at 1000 Hz at 50 dB HL.
 I always use a pulsed puretone, as it is preferred for
patient’s with tinnitus. In addition, it is important to vary the
timing of your presentation of the tones so the patient isn’t
guessing at a pattern

6. Puretone Threshold Symbols
Note: Bone conduction thresholds obtained on the forehead are
indicated by a ^ symbol.

7. Normal Hearing
 Normal AC and BC
thresholds
 Many different
scales exist
regarding degree
of HL
 For the purposes
of this class, we
will use the scale
on the next slide.

8. Degree of Hearing Loss
 This is the exact scale
that I use in interpreting
audiograms
 Some clinics are more
liberal and consider
normal hearing to be any
threshold up to 25 dBHL
 In determining the
degree of loss, the
textbook approach would
be to calculate the
puretone average
(PTA=average dB of AC
thresholds at .5, 1, 2
kHz) and compare the
PTA to the scale at right.
From: Northern, J. He aring Diso rde rs (3rd
ed)

9. Configuration of HL
 Flat
 Thresholds within 20dB of each other across all
frequencies
 Rising
 Low frequency thresholds are at least 20dB poorer than
high frequencies
 Sloping
 High frequency thresholds are at least 20dB poorer than
low frequencies
 Precipitous
 High frequency thresholds worsen by at least 20dB per
octave

10. Disorders of the Outer & Middle
Ear
 Causes a conductive hearing loss (CHL)
 On the audiogram, you would find normal bone
conduction thresholds and abnormal air
conduction thresholds
 Tympanograms (test of middle ear function) will
be abnormal

11. Conductive Hearing Loss
 Normal BC
thresholds
 Abnormal AC
thresholds
 An air-bone gap is
present at .5, 1, 2,
and 4 kHz
 WRS should be
nearly normal, as
there is no
Image from: telemedicine.orbis.org
This patient has a mild CHL

12. Abnormal Tympanograms
Type B=flat Type C=negative
pressure

13. Abnormal Tympanograms
Type As=stiff,
hypocompliant
Type AD=flaccid,
hypercompliant

14. Outer Ear Pathologies
 Anotia
 absence of the outer ear
 Microtia
 malformation of the outer ear
 Wax build-up
 Otitis Externa
 aka swimmer’s ear or outer ear infection (bacterial)
 Atresia
 absent or closed earcanal
 Stenosis
 narrowing of EAC
 Otomycosis
 fungal infection of EAC
 Exostoses
 bony growth in EAC, common in cold water swimmers
 Osteoma
 bony tumor in EAC

15. Tympanic Membrane
Pathologies
 Myringitis
 inflammation of TM
 Tympanosclerosis
 thickening and scarring of the TM
 Perforation
 hole or tear in the TM
 May be caused by fluid pressure due to otitis media,
barotrauma (rapid pressure change due to flying or
scuba diving), or self-inflicted (q-tip use)

16. Middle Ear Pathologies
 Otitis media (OM)=middle ear infection
 Otitis media with effusion (fluid)
 May be acute (sudden onset) or chronic (long-lasting)
 Eustachian tube dysfunction
 malfunction of Eustachian tube
 Causes retraction of TM and popping, crackling, pressure,
pain
 Patulous Eustachian tube
 Eustachian tube is stuck open (patent)
 Autophony, hearing one’s own voice in head, is common
complaint
 Otosclerosis
 Bony growth over stapes footplate and fixation to oval
window
 Ossicularchain discontinuity
 Loss of connection between the ossicles; usually due to
head injury
 Cholesteatoma
 An erosive tumor composed of skin, protein, and fats

17. Treatment for Conductive HL
 Medical
 Antibiotic eardrops, oral antibiotics for bacterial infections
 Surgical
 Myringotomy (incision in TM), pressure-equalization tubes,
ossicular repair, stapedectomy (removal of stapes and
prosthesis placement)
 Amplification
 CHL is very easy to fit with a hearing aid(s)
 Because the sensory cells of the cochlea are healthy, CHL
only requires amplification to power through the middle ear
pathology. Once the sound gets past the middle ear
problem, it is clearly transmitted through the remainder of
the auditory system with ease.

18. Collapsing Canals
 If you ever discover a conductive hearing loss
component in the high frequencies when you
are using traditional headphones, it is
necessary to retest your air-conduction
thresholds using inserts.
 The pressure of traditional headphones can
actually cause a collapse of the ear canal in
some patients (especially true in the elderly)

19. Disorders of the Inner Ear
 Results in a (primarily) sensorineural hearing
loss (SNHL)
 On the audiogram, you would find abnormal bone
conduction and air conduction thresholds
 Tympanograms (test of middle ear function) will
usually be normal

20. Sensorineural Hearing Loss
 Abnormal AC and BC
thresholds
 No air-bone gap
 WRS will vary depending
on degree of loss and
cochlear vs. neural
damage
 According to the PTA
method of determining
degree of HL, this patient
has a slight SNHL.
 However, due to the
sloping configuration, it is
more accurate to define
the loss as a slight-
sloping-to-severe SNHL.
Image from: telemedicine.orbis.org

21. Normal Tympanogram
Tests middle ear function
= eardrum, ossicles,
eustachian tube
Measures changes in the
movement of the eardrum
Type A=normal

22. Inner Ear Pathologies
 Presbycusis
 Age-related hearing loss; effects the high frequencies first
 Noise-Induced Hearing Loss (NIHL)
 Exactly like it sounds; dependent on intensity, duration, and type
of noise exposure, classic “noise notch” seen from 3 to 6 kHz,
with recovery at 8 kHz
 Meniere’s disease
 Overacummulation of endolymph in the cochlea; characterized
by attacks of vertigo, tinnitus (roaring), low-frequency SNHL
(usually unilateral), nausea/vomiting
 Ototoxicity
 High-frequency SNHL due to damaging effects of certain drugs
(most notably aminoglycoside antibiotics and platinum-based
chemo drugs)
 Perilymph fistula
 Hole (fistula) at the oval window, in which perilymph leaks into
middle ear. Fluctuating HL (SNHL or Mixed HL) and dizziness
common.
 SuperiorSemicircularCanal Dehiscence
 Hole or thinning of the bony lining of the superior SCC;
symptoms: fullness, autophony, dizziness with/sensitivity to loud
sounds, low-frequency CONDUCTIVE hearing loss with normal
tympanogram

23. A note about sudden hearing
loss
 Sudden, idiopathic sensorineural hearing loss is any
SNHL that occurs very suddenly with no identifiable
cause
 Usually unilateral
 May be partial or complete loss of hearing
 Often accompanied by dizziness and tinnitus
 Requires IMMEDIATE medical referral
 Do not assume that a patient has wax, an infection, or a
broken hearing aid if they call complaining of a sudden
inability to hear. If you can’t see them ASAP refer them to
their primary doctor or an ENT for a same-day
appointment, if possible. Steroid treatment that occurs
within the first week of the hearing loss may result in
improved/recovered hearing.

24. Mixed HL in the Right Ear
 Mixed hearing loss
(MHL) is a
combination of
sensorineural hearing
loss with a conductive
HL component
 Commonly seen in
older adults with
presbycusis and
middle ear disorder
 May be seen in cases
of perilymph fistula,
head injury,
barotrauma
Imagefrom:
asha.org

25. Mixed Hearing Loss
 Abnormal AC and
BC thresholds
 Air-bone gap
present
 Expected WRS
based on BC
thresholds
 This patient has a
mild to moderately-
severe MHL.
Image from: telemedicine.orbis.org

26. Treatment for MHL
 Because MHL is a combination of CHL and
SNHL, the treatment should also take a
combined approach
 Always refer to ENT for medical treatment
FIRST
 Finally, amplify the hearing loss that remains

27. Acoustic Neuroma
 A benign (non-cancerous) tumor that grows on the
auditory nerve (CN VIII)
 Also referred to as an aco ustic tum o r or ve stibular
schwanno m a
 Occur at a rate of 1/100,000 every year
 In 95% of cases, tumors are unilateral (one ear only)
 Classic signs of acoustic neuroma
 Asymmetrical, sensorineural hearing loss in the high
frequencies
 Poorer word recognition score in affected ear
 Unilateral tinnitus
 May also be associated with dizziness
 If the tumor is big enough to press on the facial nerve (CN
VII), may report facial weakness/numbness

28. Audiogram of Patient w/ Acoustic
Neuroma (Right ear)
Image from: f1000prime.com
Right Left
WRS(
%)
76 100

29. Diagnosis of Acoustic Neuroma
 It is important that you refer patients to an ENT
physician if they exhibit an asymmetrical
hearing loss and unilateral ear symptoms
 Auditory brainstem response (ABR) testing
may be performed by an audiologist
 Magnetic resonance imaging (MRI) of the
internal auditory canals is the gold standard
for diagnosis, as ABR testing may miss small
tumors

30. Hearing Aids in Patient’s with
Acoustic Neuroma
 May wear a hearing aid in the affected ear, but
hearing should be tested regularly to monitor
for changes in hearing sensitivity and speech
understanding

31. Always keep these FDA
Regulations in mind… If any of the following conditions exist, a patient must
be referred for a medical evaluation by a physician
(preferably an ENT):
 Visible congenital or traumatic deformity of the ear.
 History of active drainage from the ear in the previous 90
days.
 History of sudden or rapidly progressive hearing loss within
the previous 90 days.
 Acute or chronic dizziness.
 Unilateral hearing loss of sudden or recent onset within the
previous 90 days.
 Audiometric air-bone gap equal to or greater than 15
decibels at 500 Hz, 1,000 Hz, and 2,000 Hz.
 Visible evidence of significant cerumen accumulation or a
foreign body in the ear canal.
 Pain or discomfort in the ear.

32. Why do we mask?
 To prevent the non-test ear (NTE) from
participating in the test (cross-hearing)
 We want to make sure that when we are
testing the right ear, that we are getting the
true threshold of the test ear (TE) and that the
NTE is not helping out
 This is necessary because of BONE
CONDUCTION!
 Our ears are housed in a bony skull, which
vibrates BOTH cochleae when sound is present
at a certain level

33. Interaural Attenuation
 Interaural attenuation (IA) is the amount of
sound that is attenuated/reduced when
crossing from one ear to the other
 The IA varies:
 Depending on the frequency
 From patient-to-patient (skull thickness)
 Depending on the transducer used (phones,
inserts, bone)

34. IA of Air Conduction -
Headphones
 The minimum IA of headphones is 40 dBHL
 If we present 80 dB to the test ear, 40 dB of
that sound is reaching the cochlea of the non-
test ear
Image from: wikipedia.org

35. IA of Air Conduction - Inserts
 The minimum IA of inserts is 70 dBHL
 If we present 80 dB to the test ear, 10 dB of
that sound is reaching the cochlea of the non-
test ear
 You are less likely to mask for air-conduction
testing when you use inserts 
Image adapted from:

36. IA of Bone Conduction
Image from: wikipedia.org
The minimum IA of bone
conduction is 0 dBHL
If we present 30 dB to the
test ear, 30 dB of that sound
is reaching the cochlea of
the non-test ear
You m ust mask for bone-
conduction testing in
conductive losses and
asymmetrical losses 

37. When to Mask-Air Conduction
 Headphones: when there is a 40 dBor more
difference between the air conduction threshold of
the test ear and the bone conduction threshold of
the non-test ear.
 Inserts: when there is a 70 dBor more difference
between the air conduction threshold of the test
ear and the bone conduction threshold of the non-
test ear.
 NOTE: Because we begin our audiogram with air
conduction testing, we assume that there is no
air-bone gap and compare air-to-air to determine
the need for masking. Occasionally, you will have
to go back and mask some AC thresholds afte r
you have actual BC thresholds to compare to.

38. When to Mask - Bone
Conduction
 When there is a 15dB or more difference
between the air conduction threshold of the
test ear and the bone conduction threshold of
the same ear
 aka: Mask for BC when there is an air-bone gap

39. Types of Masking Noise
 Puretone Testing
 The masker is a narrow-band noise (NBN) that is
centered around the test frequency
 Speech Testing
 The masker is a wide-band noise that consists of
sound energy from 300-3000 Hz

40. How Much Noise?
 Well, you need to “cover up” the NTE….so, the
level of the masking noise has to be greater
than the patients AC threshold in the NTE, but
not so loud that overmasking occurs.

41. Undermasking
 Not using enough noise in the non-test ear
 The obtained threshold is really the response
of the non-test ear

42. Overmasking
 Using too much noise
 The obtained threshold is exaggerated when
the masker crosses the head and shifts the
threshold of the test ear.
 Traditionally, we use the plateau method to
ensure that we have obtained a true threshold
and are not undermasking or overmasking.

43. The Plateau Method
 Always start with the noise 10 dB above the AC
threshold of the NTE
 With noise in the NTE, present the tone in the test
ear at threshold level
 If the patient hears the tone, increase the masking noise in
the NTE by 5 dB
 If the patient does not hear the tone, increase the tone in
the TE until the patient responds
 After the patient responds to the tone with three
consecutive, 5 dB increases of noise in the NTE,
you have achieved your plateau, and the patient’s
masked threshold can be recorded.

44. Occlusion Effect
 During masking for bone conduction, the bone
oscillator is on the TE mastoid, while the NTE is
plugged up with a phone or insert.
 In this situation, the occlusion of the plugged up,
non-test ear will actually increase the likelihood
that the NTE will respond to the tone (especially at
.25, .5, and 1 kHz).
 As a result, the patient’s occlusion effect must be
added to the AC threshold of the non-test ear at
the onset of masking.
 It’s recommended to add an extra 10 dB at .25 and .5
kHz and an extra 5 dB at 1 kHz. So instead of starting
your masking at 10 dB above the NTE threshold at .25
kHz, you would start your masking at 20 dB above the

45. The Masking Dilemma
 In bilateral, conductive hearing losses, the
amount of masking noise required is often
sufficient to result in overmasking and a
shifting of the true threshold.
 In these cases, it is best to record the
unmasked thresholds and note below the
audiogram, “could not mask-masking
dilemma”

46. Pearls of Wisdom
 When in doubt, mask
 Using insert earphones will greatly reduce the
need for masking due to a higher interaural
attenuation
 Inserts also reduce the risk of overmasking
 Ask the patient to tell you which ear they hear
the beeps in (if they can)

47. SRT
 Speech reception threshold (SRT)
 The softest level (dB HL) at which a patient can
accurately repeat spondees (two-syllable words;
i.e. baseball, hotdog, birthday) 50% of the time
 SRT is primarily used as a reliability check
 In comparing the SRT to the PTA, they should be
within 10 dB of each other
 The patient should be able to repeat words about as softly
as they can hear tones at .5, 1, and 2 kHz
 If you have poor SRT-PTA agreement, then the
reliability of your results should be considered to be
questionable

48. SRT procedure
 Same procedure as determining thresholds for tones
 Tell the patient: “You will hear some soft two-syllable words.
Please repeat the words as best as you can. If you’re not sure of
a word, please try to take a guess.”
 Start at the patient’s most comfortable level
 Use the same bracketing technique as puretone testing
 If they repeat word correctly, decrease intensity by 10 dB
 If they miss the word, increase intensity by 5 dB
 SRT is the softest level at which the patient accurately
repeats spondees 50% of the time with at least 3 correct
responses at that intensity

49. Masking for SRT
 Just like masking for puretones
 Determine the need for masking and use plateau method to determine effectively
masked threshold for speech
 Consider the interaural attenuation (IA):
 40 dB for headphones
 70 dB for inserts
 0 dB for bone (you probably won’t do a bone-conducted speech test, though it is
possible and very useful in children)
 The same rules apply for speech
 Take your SRT in the TE minus the be st bo ne co nductio n thre sho ld in the NTE. If
that value is greater than the IA, you need to mask.
 Example, if your SRT using traditional headphones is 50 dB in the TE and the best BC
threshold in the NTE is 5 dB (50dB-5dB=45 dB), you need to mask since 45 dB is greater
than 40 dB.
 ***Note: usually you have not yet performed BC when you are performing SRT, so
assume air=bone. Alternatively, you can subtract the SRTof the NTE fromthe SRTof
the TE to determine the need formasking. Just keep in mind that the SRT is an air-
conduction test and you mask based on the BC scores of the non-test ear.

50. Masking for SRT
 How much noise?
 If you’ve determined the need for masking, add
10 dB to the SRT of the non-test ear and present
a spondee at threshold
 Just like puretone masking utilizing the plateau
method, if they get the word correct, then
increase masking by 5 dB and present another
spondee and repeat until your 15 dB masking
plateau is achieved. Or, if they cannot repeat the
spondee, increase the presentation level in 5dB
steps until threshold is reached and plateau your
masking level accordingly.

51. WRS
 Word recognition score (WRS)
 The percentage of phonetically-balanced,
monosyllabic words that a patient can accurately
repeat
 Presented at either MCL (most comfortable level) or
MIL (most intelligible level)
 This is generally thought to be approximately 30-40 dB SL
re: SRT
 A pre-recorded list of 25 to 50 words should be
presented to each ear
 Most common word lists: CID W-22 and NU-6
 Each word should be preceded by a carrier phrase:
 “Say the word pick”
 “Say the word ro o m ”

52. WRS
 When scoring a patient’s performance on WR
testing, you must remember that wrong is
wrong!
 The patient should only be given one attempt at
each word (oftentimes if they miss a word the first
time, they will ask you to repeat it…don’t)
 Close isn’t correct
 i.e. If they say the word “eats” for “eat”

53. WRS in determining site-of-lesion
 Patient’s with normal hearing or conductive
hearing loss will perform normally on WR
testing
 Patient’s with only high-frequency or a mild,
flat SNHL will also generally perform near-
normal
 The more severe the SNHL, the poorer a
patient will perform on WR testing
 Neural losses result in poor performance

54. WRS in determining site-of-lesion
 Asymmetrical WRS, especially in the presence
of puretone asymmetries, should be
considered a “red flag” for an acoustic
neuroma
 In patient’s with a retrocochlear lesion, roll-
over may also be present on WR testing. This
means that with increased presentation level,
the patient’s performance will actually
decrease (i.e. 56% at 85 dB decreasing to
12% at 95 dB).

55. Masking for WRS
 You will be much more likely to mask for WRS than SRT since WRS
is a supra-thre sho ld test
 Consider the interaural attenuation (IA):
 40 dB for headphones
 70 dB for inserts
 0 dB for bone (you probably won’t do a bone-conducted speech test,
though it is possible and very useful in children)
 The same rules apply for speech
 Take your presentation level in the TE minus the be st bo ne co nductio n
thre sho ld in the NTE. If that value is greater that the IA, you need to
mask.
 Example, you are performing WR testing using traditional headphones at 75 dB
in the TE and the best BC threshold in the NTE is 20 dB (75dB-20dB=55 dB).
So, you know you need to mask since 55 dB is greater than 40 dB.
 ***Note: usually you have not yet performed BC when you are performing
WRS, so assume air=bone. Alternatively, you can subtract the SRT of the NTE
from the presentation level to determine the need for masking, but, again, the
SRT is an air-conduction test.

56. Masking for WRS
 How much noise?
 If you’ve determined the need for masking, add
10 dB to the SRT of the non-test ear + an extra
15 dB for your plateau. So…
 Noise in NTE = SRT of NTE + 25 dB
 Ex: The SRT of the NTE is 30 dB, so you add 25 dB to
arrive at your masking level of 55 dB in the NTE.
 With symmetrical SNHL, it is often a quick “shortcut”
to set your masking noise at 20 dB below the
presentation level

57. Most Comfortable Level (MCL)
 The dB level of speech that the patient
feels is most comfortable.
 Measured with a cold-running speech stimulus (i.e.
the Pledge of Allegiance, nursery rhyme, etc)
 May be performed monaurally (one ear at a time) and
binaurally (both ears at same time)
 Recall the advantages of binaural hearing?
 The binaural MCL will be about 5 dB less than the individual
MCLs for fairly symmetric losses
 Start at ~20 dB above the patient’s SRT and gradually
increase the intensity until the patient reports that the
speech is “comfortable”
 Many clinicians perform word recognition testing at
the patient’s MCL

58. Uncomfortable Loudness (UCL)
 The dB level of speech that the patient
feels is uncomfortable.
 Measured with a cold-running speech stimulus (i.e.
the Pledge of Allegiance, nursery rhyme, etc)
 Begin speaking at MCL and ascend until the patient
reports that speech is uncomfortable
 Because MCL and UCL measure
loudness across a broad frequency
spectrum, they are difficult to use when
programming multi-channel hearing aids

59. Loudness Discomfort Level
(LDL)
 The loudness discomfort level (LDL)
is the level at which the patient
reports sound to be uncomfortably
loud at specific frequencies
 Stimuli: pulsed tones or narrow bands
of noise at .5, 1, 2, 3, and 4kHz

60. Loudness Scaling to Determine
LDL
 When performing
LDLs, the patient is
asked to rate the
loudness of
frequency-specific
stimuli (i.e. pulsed
tones)
 It is best to provide
loudness anchors
such as the Cox
loudness descriptors
(at right) rather than
just having the
patient raise their
hand when the sound
is uncomfortable
Image from:
http://www.harlmemphis.org//index.php?cID=138

61. Clinician Instructions for Measuring
LDLs
 Begin slightly above threshold at 1kHz and use an
ascending technique to present pulsed tones
 Ascend in 5 dB steps for patients with threshold at or
below 50dBHL
 Ascend in 2 dB steps for patients with thresholds
above 50dBHL
 Determine the patient’s LDL, which is the level
that they rate as #7, uncomfortably loud
 Repeat twice at each frequency and take the
average LDL for the three trials
 Common LDL frequencies are .5, 1, 2, 3, and 4 kHz
 If you are pressed for time, .5 and 3 kHz will provide
you with good, useable information

62. Converting dB HL to dB SPL (real-
ear)
 When measuring LDLs on the audiometer, the
LDL will be in dBHL; however, hearing aid output
is in dB SPL
 You CANNOT make a direct comparison of the
patient LDL in dB HL to the hearing aid MPO in
dB SPL
 Remember, 0dBHL at 1000 Hz
(headphones)=7dBSPL in the open soundfield. This is
referred to as the RETSPL, which stands for real-ear
threshold in sound pressure level.
 But, what is that dB level when there is a hearing aid
in the ear, which decreases the physical
volume/space of the ear canal and increases the

63. Converting dB HL to dB SPL (real-
ear)
 The conversion formula is as follows:
 LDL in real-ear SPL=LDL in HL + RETSPL +
RECD
 Refer to the Audiology Online presentation: “How
Loud is Too Loud? Using Loudness Discomfort
Level Measures for Hearing Aid Fitting and
Verification, Part 2”
http://www.audiologyonline.com/audiology-ceus/cours

64. RETSPL Values – Most
Common
500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz
Headphone
s (TDH 39)
11.5 7.0 9.0 10.0 9.5
3A Inserts
(HA-1)
6.0 0.0 2.5 2.5 0.0

65. Real-Ear-to-Coupler Difference
(RECD)
 Ideally, you would measure the patient’s
individual RECD . However, it is usually safe
to use average RECD values.
 Average RECD values are provided below
from Dr. Mueller’s AO presentation:

66. Average REDD Values
 RETSPL + RECD=REDD (real-ear-to-dial
difference)
 I’ll make it very simple for you. Take your LDL
in dB HL and add the average REDD values
(adult) below to arrive at your LDL in dB SPL
in the real-ear!500 Hz 1000 Hz 2000 Hz 3000 Hz 4000 Hz
Headphone
s (TDH 39)
15.5 15.0 16.0 18.0 22.5
3A Inserts
(HA-1)
10.0 8.0 9.5 10.5 13.0