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Audiometric Masking
Febryanti P SariSupervisor : Dr. Yussy Afriani Dewi,dr., M.Kes.,
SpTHT-KL(K).,FICS
Department of Otorhinolaryngology Head & Neck SurgeryFaculty of Medicine Universitas Padjadjaran
RS Hasan Sadikin Bandung
2016
04/27/2023 2
Audiometry (from Latin: audīre, "to hear" and metria, “to measure") is a branch of Audiology and the science of measuring hearing acuity for variations in sound intensity and pitch and for tonal purity, involving thresholds and differing frequencies.
audiometric tests determine a subject's hearing levels with the help of an audiometer
Patrick J. Willems (2004). Genetic hearing loss. CRC Press. pp. 34–. ISBN 978-0-8247-4309-3. Retrieved23 June 2011.
AUDIOGRAM
Masked Air
Definition The process by which the threshold of
hearing for one sound is raised by the presence of another (masking) sound and the amount by which threshold of hearing for one sound is raised by the presence of another (masking) sound expressed in decibels
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
Why do we mask? To prevent the non-test ear (NTE) from
participating in the test (cross-hearing) 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
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 6
WHY? Cross Hearing!
Key Concept=Interaural attenuation! The amount of sound required to bridge across the head and stimulate the opposite cochlea by BC.
Unmasked thresholds trace out a “shadow curve” displaced from the non-test ear by the size of IA.
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 8
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)
Interaural Attenuation value based on frequency and type of transducer (Stach)
10
Frrequency
Supra-aural (TDH 49)
Insertphone (ER-3A)
Vibrator BC
(Hz) (dB) (dB) (dB) 250 40 75 500 40 75 0 1000 40 60 0 2000 45 55 0 4000 50 65 0 8000 50 65
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IA minimum by Goldstein and Newman
IA of Air Conduction - Headphones
The minimum IA of headphones is 40 dB HL
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
IA of Air Conduction - Inserts The minimum IA of inserts is 70 dB HL 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: wikipedia.org
IA of Bone Conduction
Image from: wikipedia.org
The minimum IA of bone conduction is 0 dB HL
If we present 30 dB to the test ear, 30 dB of that sound is reaching the cochlea of the non-test earYou must mask for bone-
conduction testing in conductive losses and asymmetrical losses
When to Mask-Air Conduction
Headphones: when there is a 40 dB or 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 dB or more difference between the air conduction threshold of the test ear and the bone conduction threshold of the non-test ear.
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
When to Mask - Bone Conduction
When there is a 10 dB 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
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 17
Type of masking noises Effectiveness and efficiency of masking
critical bandwith signal to be masked and type of masking noise used
White noise Narrow band noise speech noise
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 18
TYPES OF MASKING NOISES
white noise or broad bandrandom energy distribution (the average is almost the same at all frequencies) are analogous to the distribution of light white color. Because spectrum is broad and flat, WN have limitations for masking pure tones
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 19
TYPES OF MASKING NOISES
Narrow band noise / NBN The most efficient is to produce a shift in the
hearing threshold of the greatest intensity is the smallest sound masking
The results of the research of the most effective masking is around the frequency of the sound in masking
NBN intensity is lower than WN NBN can produce a shift in the threshold
without causing disruption due to masking intensity is too hard
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 20
Effective masking level The amount of intensity noise that
should be given to prevent cross hearing
Minimum masking Maximum masking Over masking
Undermasking Not using enough noise in the non-test
ear The obtained threshold is really the
response of the non-test ear
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
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.
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 23
PROBLEM IN MASKING
Central masking the increase in the threshold of hearing ear
being tested at the time of masking test starts (not yet achieve effective masking)
central masking between 5 —15 dB (usually around 5 dB)
oclussion effect Raising the threshold of hearing in the
closed ear due to the occlusion effect Commonly bone conduction with masking
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 24
TRANSDUSER TYPES
Headphone / earphone Insertphone vibrator
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MASKING METHOD
Plateau method
formula method
step masking method
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PLATEAU (HOOD) METHODWidely used in the United KingdomLess desirable because the long test timeIt is recommended if the minimum and maximum masking area is very narrowProvide sound masking intensity increased gradually until it reaches a plateau which indicates that the threshold is actually in the ear being tested has been reached
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 27
PLATEAU METHOD
Finding the threshold of the ear being tested (without masking)
Then the masking noise of 10 dB SL give to the ear not being tested and the hearing threshold test is repeated
Each time the masking sound intensity is raised 10 dB, the ear hearing threshold test is repeated
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 28
PLATEAU METHOD
During the masking intensity is still under masking, any increase in the intensity of 10 dB will shift the hearing threshold of 10 dB
At a certain intensity, the increase in 10dB masking is no longer shifting threshold
Two increases masking noise by 10 dB, no longer shifting threshold reach plateau
Effective masking has been reached
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 29
FORMULA METHOD
Air conduction Masking minimum (Mmin) = AC
threshold in TE –IA + A-B gap in NTE
Masking maximal (Mmax) = threshold BC in TE + IA
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 30
FORMULA METHOD
Bone conduction Masking minimum (Mmin) = BC TE +
A-B gap NTE Masking maximum (Mmax) = BC TE +
IA note: Mmaks < UCL
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 31
INITIAL INTENSITY MASKING (Sataloff)
Avoid under masking Easing achieve effective masking
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 32
MASKING INITIAL INTENSITY (Sataloff)
Air conduction tests effective initial intensity is the intensity of
the initial masking as a guide at the start of the hearing threshold shift in the ear being tested
Sataloff performed on the intensity of the air conduction threshold of the ear not being tested + 30 dB
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 33
Condition need masking for AC AS
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MASKING INITIAL INTENSITY (Sataloff)
Bone conduction test Bone conduction starts at the air conduction
threshold of the non test ear + 20 dB If the masking threshold ear in normal or
sensorineural deafness, should be added to 15dB at 250-500hz,and 10dB at 1000 Hz, which is the correction factor occlusion effect on the closed ear headphones
Above 1000 Hz occlusion effect is very minimal Conductive deafness not need the added value
occlusion effectAudiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 35
>
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STEP MASKING method(Katz dan Lezynsky)
Faster than methods plateau The increase in the intensity of masking
methods plateau only 5-10 dB each time, step masking using greater intensity =
20 dB Masking begins with providing EML
(Effective Masking Level) of 30 dB SL (Sensation Level)
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 37
METODE STEP MASKING (Katz dan Lezynsky)
If the masking threshold after administration shifted by 15 dB or more required additional masking (subsequent masking / submask) of 20 dB
If the administration of the initial masking 30 dB SL EML no threshold shift or just a 5-10 dB, the likelihood is that the actual threshold (no cross-over hearing) so it does not need to be supplemented submask
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 38
STEP MASKING METHOD (Katz dan Lezynsky)
CRITERIA AFTER INITIAL MASKING QUOTE FROM Abiratno.2005Threshold shifting with EML 30dBSL
need/not submask
0-10 dB No need15 dB possibly no need20 dB Possibly need to25 dB Need to
04/27/2023 39
STEP MASKING METHOD(Katz dan Lezynsky)
If the threshold in the ear being tested eased after the initial masking (30 dB SL EML)
The number of shifts in the ear threshold test showed indications of whether or not an additional masking / submask
If after submask summed (20 db above masking initial EML), an indication of the need to shift the threshold / absence of additional submask
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 40
METODE STEP MASKING (Katz dan Lezynsky) Criteria after giving subsequent masking by Abiratno.2005
Threshold shifting with EML 20dBSL
Need/not submask
0-10 dB No need15 dB Possibly no need20 dB Possibly need> 20dB Need to
Masking for Speech Reception Threshold
Just like masking for puretones› Determine the need for masking and use
plateau method to determine effectively masked threshold for speech
› Minimum IA 45dB› Initial level masking 30dB› Subsequent mask is 20dB
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 42
Masking for word recognition score(WRS)
Wrs doesn’t count hearing threshold,only using one level intensity
Using widely spectrum noise masking Level masking of the non test ear 30dB
Audiology: Diagnosis. Edited by Roeser, Valente, and Hosford-Dunn. Thieme Medical Publishers,Inc., New York.2000
04/27/2023 43
conclusion Masking may be necessary if one normal
ear and one ear of a hearing loss, or if there is an asymmetrical hearing threshold
Inspection begins frequency 1000 Hz The purpose masking to determine the
actual threshold of the ear suspected of having hearing problems and avoid the tested crossings from ear to ear not being tested (cross hearing)
04/27/2023 44
Given the time needed to carry out the masking procedure, then we need to understand a clear indication when required masking and masking effective intensity for each frequency being tested
If we doubt the diagnosis of hearing, whether conductive hearing loss (CHL), nerve deafness (Sensorineural hearing loss) or deafness mixture (SFM), absolutely necessary masking
04/27/2023 45
With audiometric we can distinguish or compare hearing threshold between conduction and bone conduction
Masking air conduction is done when there is a difference between AC and BC on both ears ≥ IA and bone conduction masking done in case A- B gap ≥10 dB
For masking procedure, in the field of audiology known three methods, namely methods plateau, method formula and step masking method
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Thank you
04/27/2023 47
Contoh penggunaan formula untuk menilai masking minimum dan maksimum
Telinga kanan: yang sedang dites Telinga kiri : gangguan konduktif ringan
dengan A-B gap : 30 dB (dikutip dati Hodgson 1980, Handbook of Clinical Audiology)
04/27/2023 48
Contoh kasus: Evaluasi pendengaran dengan
menggunakan metode step masking Kasus dengan gangguan pendengaran
unilateral kiri. Telinga kanan: Normal (AC dan BC rata-rata 10 dBHL). Telinga kiri : ambang AC tanpa masking rata-rata 55 dBHL tertera pada tabel 3.10
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METODE FORMULA
Formula Masking untuk tes hantaran udara
Mmin = At – 40 + (Am – Bm) Mmaks = Bt + 40 dengan catatan Mmaks
kurang dari UCL (uncomfortable loudness level)
NB: Nilai IA minimum untuk semua frekuensi yang dipakai dalam metode formula : 40 dB
04/27/2023 52
Berdasarkan pada panduan besar IA minimum untuk hantaran udara, semua frekuensi perlu di masking kecuali 4000 Hz dan 8000 Hz (besar IA lebih kecil dari IA minimum pada masing-masing frekuensi)