Masking flashcards |

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Masking

-NOISE ALWAYS IN BETTER EAR!! (NTE)

-The noise that you put in the ear you're not testing.
-We mask b/c it is possible that the good ear is hearing the sound.

Interaural Attenuation (IA)

-Amount of sound energy lost as sound travels from one ear to another via bone conduction
-Most often related to bone conduction
-Varies from person to person (we mask to be sure)
-Varies across signal
-You have to be above this level before they can hear it; how much is lost

Conservative Values

-Clinical experience will have a clinician decide when to not use conservative values
-Can view patient's own Interaural attenuation to make decision as well
-Methods may also affect with plateau allowing person to be able to allow higher levels.

IA Conservative Values:
Pure-tone AC

•Headphones- 40 dB HL

•Inserts- 50 dB HL; depends on how well you got the insert in the ear

IA Conservative Values:
Pure-tone BC

•0 dB; but can vary from person to person

IA Conservative Values:
SRT

•Headphones- 45 dB HL

•Inserts- 50 dB HL

IA Conservative Values:
WR

•35 dB HL

•WR is 30 or 40 dB SL above SRT threshold. Because we jump so much louder Interaural attention will crossover much quicker b/c we are louder.

When to Mask:
AC

•A 40 dB difference b/w AC of the test ear and the non-test ear

•AC(TE) - AC(NTE) ≥ 40 dB HL (50 dB HL)
•AC(TE) - BC(NTE) ≥ 40 dB HL (50 dB HL)

How to Mask:
AC

•Better ear + Pad (10 to 15 dB)

•AC(NTE) + pad (10 to 15 dB)

When to Mask:
BC

•AGB ≥ 15 dB

How to Mask:
BC

•Better ear + pad (10 to 15 dB) + OE
•AC(NTE) + pad + OE

Occlusion Effect (OE) for BC

•250 Hz: 20 dB
•500 Hz: 15 dB
•1000 Hz: 5 dB

When to Mask:
SRT

•SRT(TE) - SRT(NTE) ≥ 45 dB HL (50 dB)
•SRT(TE) - Best Bone(NTE) ≥ 45 dB HL (50 dB)

•PTA and SRT are not in agreement (7-10 dB diff.)

How to Mask:
SRT

•PL SRT(TE) - 35 dB

When to Mask:
WR

•PL WR(TE) - SRT(NTE) ≥ 35 dB HL
•PL WR(TE) - Best Bone(NTE) ≥ 35 dB HL

•When SRT(NTE) and WR(TE) differ by 30 dB

How to Mask:
WR

•PL WR(TE) - 25 dB

Crossover

what gets to the other side in the NTE

Shadow Curve

hearing loss that mimics the other ear that is only different by Interaural attenuation. When you mask it, it will shift and become something else. Uncertain of the hearing loss when you mask it.

Plateau Method

•Use for masking AC & BC
•Range of intensities (b/w under- and over- masking) that will permit effective masking. This is possible when the thresh in the TE remains the same when masking is successfully increased in the NTE by 5 dB (3x consecutively)


•The starting point is the masking level for either AC or BC
•If they hear the tone, masking goes up 5 dB
•If they don't hear tone, the tone goes up 5 dB
•When we reach their real threshold, it doesn't matter how loud the masking gets

Minimal Masking Level

-you could start without the pad, you will just have to turn it up a lot more; the minimum it is going to take mask

-Plateau: start at starting level, present tone. If they get it the noise goes up. If they don't turn the tone up. You need to turn the noise up 3 5 dB steps in order to get the plateau

Undermasking

When the test signal will still be perceived in the NTE b/c of an insufficient amount of masking noise presented to the NTE

Overmasking

happens when there is a conductive component in both ears. The noise can crossover too. When the level of the IA for noise is over 40. You can no longer get a threshold on the side you are testing. Use inserts b/c the IA is higher, therefore you will have less crossover

Effective Masking

-how much is it going to take for that cochlea to not pick it up

•crossover + pad (10 to 15 dB)

Central masking shift

whenever you put noise in the ear, your brain tries to shut the noise down b/c it recognizes that its noise and it tries to turn it down to "ignore" it -> this is how we hear in noise. When you out noise in their threshold may shift 5-10 dB because of the noise.

Masking with difficult populations

EXAMPLE:
You can mask for a child that doesn't understand the directions or has intellectual disabilities or deficits by "listening for the birdie in the wind".

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