Lecture 5 Flashcards
What is masking?
The raising of the threshold of audibility of a sound by the presence of another (masking) sounds.
Can isolate the non-test ear by putting masking noise into it.
Separate the ears, know which ear is “distracting” out of the picture, focus on the ear that needs to be tested.
What is another definition of masking?
A carefully controlled amount of noise with specific acoustic characteristics, introduced to the non-test ear, when interaural attenuation has been exceeded, that is when there is danger of the signal in the test ear being heard.
What are the symbols for RE tested with noise in the LE, and LE tested with noise in the RE?
RE/LE = triangle LE/RE = square
Place on audiogram in reference to AC threshold of worse ear.
What is the TE and NTE?
TE = the ear to which the test signal is being directed NTE = the ear to which is not being tested but which we are concerned may be hearing the test signal.
What is central masking?
The threshold shift in the TE resulting from the introduction of masking into the NTE that is not due to crossover (not over-masking). Changed by about 5dB.
Just an effect of noise.
What is the occlusion effect?
Improvement in BC thresholds for frequencies < 1000Hz when the ear canal is occluded
Amplifies the sound signal - air spaces with resonances that can amplify sound, creating air space in the auditory canal.
What is white noise?
Composed of random energy with approximately equal intensity at all frequencies
What is narrow band noise?
White noise passed through a series of band-pass filters with different centre frequencies.
What is speech noise?
Speech-shaped noise has a spectrum that approximates that of the long-term spectrum of speech.
What is effective masking?
The dB level of a noise that just masks a signal of that level when both are present in the same ear.
dB EM
Just the right amount to mask the signal, by introducing the least amount of energy possible to make it still effective.
What are the values for IA for supra-aural and inserts (for AC)?
What is the value for IA for BC?
Supra-aural: 40dB difference
Inserts: 55dB difference
BC: 0dB difference - both cochlea stimulated at the same intensity.
When asking the question of do we need to mask, what do you consider?
The dB difference (IA) and the asymmetry.
When do we need to mask?
Whenever there is the possibility of the signal in the TE crossing over and being heard by the NTE.
What ear do you put masking into?
Put masking in NTE to determine what can be heard by the TE.
If right ear is bad, put noise in the left (vice versa).
When do you mask for BC?
What could this mean?
When the air-bone gap of the test ear exceeds 10dB, masking is needed for bone conduction in the NTE.
Could be a conductive/sensorineural - don’t know until mask.
