SLHS 654 Principles of Masking Study Guide

Define masking. What’s it;s purpose?

Elevation in threshold for one signal by intro of second signal. Used to determine the true degree of hearing loss with significant asymmetry between ears OR to differentiate conductive vs sensorineural loss

Define interaural attenuation and how to use it

Difference in intensity between stimulus delivered to test ear and the amount that is lost as it crosses over to the NTE. Use min of 40 dB to avoid cross hearing

What is effective masking?

Calibrated amount of noise that’ll l provide a threshold shift to corresponding dBHL

Rule for masking air conduction thresholds

If AC threshold of TE is 40dB more than BC of NTE, cross over may occur, and masking is necessary

Rule for masking bone conduction thresholds

When there is a greater than 10dB air bone gap in the same ear, same frequency, masking is frequency

Describe differences in masking noises, and why each one is more effective at masking particular stimuli

Narrow band noise: masking for pure tones

White noise (wide/broad band): many audiometers have white noise built in, use in masking speech stimuli

Plateau method

Masker is increased in 5dB steps 3 times if the TE threshold doesn’t change

Overmasking

Occurs when masker in NTE is presented so loud it crosses over the head and raises threshold in test ear

Central masking

An elevation in threshold in the test ear as a result of masking noise in NTE even though the noise isn’t intense enough to cross the skull to the TE. Cause isn’t understood, but it is probably mediated by the efferent pathway (a central phenomenon). Threshold increase=5dB (not a cause for concern)