Present by Dhruvo

2. Topic : Masking
Presenting by
Tukir Rahman (Dhruvo)
BSc in ASLP (1st batch)

3. WHY DO WE DO MASK
• To prevent the non-test ear(NTE) from participating in the test. (cross-hearing)
• That the Non-test ear is not helping out the test ear.
• This is necessary for Bone Conduction.
Because :
our ears are housed of bony skull,
which vibrates both cochlea
when sound is present.

4. INTERAURAL ATTENUATION
80 dB _+40 dB
Amount of sound that is crossing

5. INTERAURAL ATTENUATION VARIES
• Depending on the frequency
• Patient skull thickness
• The transducer which used. ( headphones, inserts, bone)

6. Air conduction Interaural
Attenuation
Bone conduction
Interaural
Attenuation
Insert Air
conduction
Interaural
Attenuation

7. WHEN TO MASK (AC)
• Headphone: When there is a 40dB or more gap between the air
conduction threshold of test and non-test ear.
• Inserts: when there is a gap 70dB or more gap between the air conduction
and bone conduction threshold of test and non-test ear.
Example : Rt ear air 50dB
Lt ear air 90dB

8. WHEN TO MASK (BC)
• When there is a 15dB or more gap between the air and bone
conduction threshold of the test ear.
Example : Rt ear air 50dB
Rt ear bone 20dB

9. TYPES OF MASKING
• Wide band (pure tone) (125-8000hz)
• Narrow band (Speech) (300–3400 Hz)

10. HOW MUCH NOISE
• Cover up the Non-test ear.
So the masking noise has to be greater then the patient AC threshold in the
Non-test ear.
Masking noise > NTE air threshold.
Example : 100 dB if Threshold is 90dB

11. THE PLATEAU METHOD
Test ear Non-test ear
AC: 30 dB AC:70dB
tone: 30dB masking: 80dB
*If the patient hear 80dB+5dB
*if the patient doesnot hear
30dB+5db
Example

13. UNDER MASKING
• Not using enough noise in Non-test ear
• In this case the non-test ear also interfere in the test ear.
• The result will
Example
Non-test ear AC 80dB
Masking noise 70dB
not acceptable

14. OVER MASKING
• Using too much noise
• The masking noise will cross the head and interfere in the test ear
(Interaural attenuation masker)
• The result will
Example
Non-test ear AC 70dB
masking noise 100dB
not acceptable

15. THE MASKING DILEMMA
• In bilateral conductive hearing loss.
• Need over masking
• True threshold is shifting ( wrong result )
In this case it is best to record unmask threshold .
And
Note below the audiogram “could not mask – Masking Dilemma”
উভয়সঙ্কট

16. IDENTIFYING THE MASKING DILEMMA
• Add the air-bone gap decibel levels
together.
• If the sum is greater then interaural
attenuation
• Then the masking dilemma will occur.
Example
Rt ear air-bone gap 45dB
Lt ear air-bone gap 35dB
Total =80dB
Suppose IA 70dB
IA < The sum of air-bone gap
The masking dilemma will occur
+

18. PEARLS OF WISDOM
When in doubt mask :
1.Use insert earphone for reduce the interaural attenuation .
2.Masking with insert earphone also reduce the risk of over masking.

19. VIDEO
• Attention all Audiologists and AuD students! Here is a fun tutorial video on
understanding clinical masking techniques.
https://www.youtube.com/watch?v=-SATWXSN64E