5 - BC: How to Mask Flashcards
Effectiveness of the masker depends on which two signal properties?
Signal level
Signal bandwidth
Speech signals use a ____ (pink noise/narrow band noise) masker
Pink Noise
Pure tone signals use a ____ (pink noise/narrow band noise) masker
Narrow Band Noise (NBN)
To mask a pure tone, a ____ (1/3, 1/2, 2/3) octave band NBN is used, centered on the pure tone frequency
1/3
What is the definition of an Effective Masking Level?
The level of masking noise required to render a signal inaudible
True or False: If the NTE is participating, then the NBN (Narrow Band Noise) will affect the threshold regardless of the level it is presented at
False: The NBN will affect threshold once the NBN reaches an effective masking level to mask the pure tone (PT) in the NTE
What is “undermasking”?
When the initial masking levels are not sufficient to “cover” the crossed pure tone (PT) signal
How do we determine how much masking to start out with?
Calculate the IML. Keep in mind, this is an estimate only, based on assumptions about the crossed BC signal
Describe the process of finding the new BC threshold using masking
- use IML to estimate minimum level of masking needed to begin
- start tone in TE at unmasked BC threshold
- when client does not respond, add 5 dB to the tone until client responds
- when client does respond, increase NBN by 5 dB
- alternate increasing masking and tone by 5 dB until you consistently get a response across at least a 15 dB increase in masking
- true masked BC threshold is the level of pure tone where NBN plateau is at least 15 dB wide
What points should you include in your instructions to your client for BC masking?
- you will hear more beeps
- respond by pressing the button every time you hear a beep
- you will also hear a noise. Ignore it and continue to listen for the beeps
- respond to the beep each time you hear it, even if it’s quiet
- do you have any questions?
