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CROSS HEARING & MASKING :forbidden: (Terminology Review (Cross Hearing…
CROSS HEARING & MASKING :forbidden:
Clinical Masking
GOAL = test signal inaudible in the NTE (minimal masking level) without affecting the true response of the rest ear (overmasking)
Masking Levels
Maximum Masking Level = (BC TE + IA) - 5 dB
Minimum Masking Level = (AC NTE + MEMC) + 10 dB (SF) + OE
Might need more masking because of OE = more likely to occur at lower frequencies (correction factors up to 1000 Hz)
Central Masking
CANS suppress signal intensity when noise is in one ear and tone is in the other (even without crossover)
~5 dB shift (reported up to 15 dB)
Terminology Review
Cross Hearing
Cross Over
Interaural attenuation (IA)
Shadow Curve
Test 125 Hz = to see if there is a downward slope = especially if you suspect Meniere's disease, you want to look for low frequency loss
Bone oscillator on the worse side = in anticipation of masking
Masking Dilemma
Use inserts
Perform SAL = sensory/neural acuity level test
Uses of SAL
Solving masking dilemma
Testing young children = that can't handle masking test
Measuring small air bone gaps
Present from forehead placement = both will receive the noise = max level allowed
Threshold without the masking noise and with the masking noise
Max level masking right on forehead, shift of 55 conductive, not much shift in SNHL because cochlea already has the loss anyway