(Masking Exam) Flashcards
masking is what? (not asking why we use it)
a way to cover up one signal from another
why do we use masking?
to make sure we are actually testing the ear we want to test
what is crossover?
sound traveling through the skull and being heard by the other ear, but at a lower intensity than the presentation in the original ear
crossover occurs via
bone conduction
why is intensity lost in crossover?
since the sound has to travel through the skull to get to the other ear
crossover occurs for who?
people with normal hearing and hearing impairments.
why don’t people with normal hearing notice crossover?
because the cross over sound is so much softer in the contra ear than the ipsi ear.
interaural means what?
between ears
if you use supra aural headphones, how much sound is attenuated as sound travels from the stimulated ear to the contra ear?
40dB in AC
when using inserts, the amount of sound attenuated when sound travels to the contra ear is ?
55dB in AC
no matter where you put the bone oscillator on your skull, it always does what?
presents the same sound intensity to both cochleas at the same time
if a person has 0dB thresholds and you present a tone at 30dB in one ear, how loud is it in the other ear? with supra aural HPs and inserts?
Supra aural HPs- -10dB Inserts- -35dB (not audible AT ALL)
supra aural HPS have a ___________ of 40dB
interaural attenuation
if you had someone with 0dB threshold and you present a tone at 70dB to one ear, the other ear will hear it at what threshold?
40dB for supra aural 15dB inserts
if a person has an ear with 80dB thresholds and 0dB thresholds in the contra ear and a 70dB tone was presented, what happens?
the originial ear does not perceive the tone, but the sound crosses over to the contra ear and that ear hears it, allowing the person to “respond” to the tone. (at 30dB for supra aural, 15dB for inserts)
if you present 20dB via a bone oscillator, what happens?
both cochleas are sent the 20dB of sound, but only the better cochlea will hear it
is there attenuation in presenting sound via BC?
no attenuation for either ear!
interaural attenuation varies depending on _________. what will we focus on and why?
varies depending on freq. we focus on 40dB for SA HPs and 55dB for inserts since this is the lowest value that all freqs. have.
what is the masking stimulus?
noise! (but there are 3 kinds of noise - white noise, narrow band noise, speech shaped noise)
what are the 3 types of masking noise?
white noise, narrow band noise, speech shaped noise
white noise is also called? what is it?
broadband noise. energy around every freq.
narrow band noise is what?
noise centered around the freq. of the test sound.
what are 2 things to know about narrow band noise? (not what it is)
-more efficient than white noise, because it centers around the freq. being tested -seems less loud to listener than white noise since it’s not encompassing as many freqs
speech shaped noise is what?
noise centered around freqs. most important for speech (500 to 2000Hz ish)
on a spectrum plot, a pure tone is _______?
energy at one freq. (one bar)
white noise that is louder than the pure tone, will show what on a spectrum plot?
will be higher in amplitude at the pure tone, but also covers the same amplitude at every single freq.
narrow band noise that is louder than a pure tone will look like what on a spectrum plot?
noise will be taller in amplitude, and surround a few freqs around the pure tone, but does not cover every freq.
Broadband noise activates ____________ whereas NBN activates _______
activates whole cochlea NBN activates cochlea around pure tone area of BM
a shadow curve is what?
an audiogram where one ear is about 40 to 55dB lower than than the other ear almost consistently across freqs.
a shadow curve is really what? (not what it looks like)
it’s showing the good ear picking up the sound presented to the bad ear, making it look like the bad ear is responding
in a shadow curve, you need to ?
mask
a square is what symbol?
left masked
a triangle is what symbol?
right masking
right masking has what symbol?
triangle
left masking has what symbol?
square
when do we mask?
when using inserts/SA HPs and there’s a chance of crossover
the test ear is?
the ear we are trying to get thresholds in
the Non test ear is?
the ear that we’re not trying to get thresholds in and needs to be presented with masking noise sometimes to prevent it from responding to sounds presented to the other ear
how does crossover occur?
-bone conduction (even when testing AC) -sometimes by sound leakage
high decibel level presented to poorer ear crosses over to better ear. What is this?
crossover
crossover is also high decibel level _________________________
presented to poorer ear, which crosses over to better ear
the interaural attenuation of BC is?
0dB
the larger the interaural attentuation, the ___________________-
louder the sound has to be before it is heard by both ears
broadband noise is also known as?
white noise
we mask in air conduction when __________ (not the equation)
when there is a chance that the signal in the test ear is being heard by the non-test ear
what’s a way to help make an educated guess as to whether a HL is SNHL or conducctive?
use other test results like tymps, ear canal volume, and acoustic reflexes
why is masking noise never presented via BC?
because IA between ears is 0, so basically you’re presenting the masking noise to both ears, even the one you’re presenting the tone to
masking is presented via what in BC?
earphones/inserts
what criterion is used to determine masking in BC?
air bone gaps
besides AC and BC, when is another situation we may need to mask in?
when testing speech
when do we need to mask in speech?
if the speech signal you are presenting at is 40dB/55dB or more above BC in opposite ear at 500, 1000, or 2000
OE stands for?
occlusion effect
OE is only a problem when?
when testing 250, 500, or 1000Hz in BONE CONDUCTION
what is minimum masking level?
smallest masking noise needed to mask a stimulus heard by the NTE due to crossover
any level of masking noise below the minimum masking level is called what?
undermasking
any level of masking noise above the maximum masking level is called what?
overmasking
what is the maximum masking level?
largest amount of masking noise that will only have a masking effect on the NTE without also masking the TE
in the equations given, if we are using inserts, what does this mean for the equations?
any equation using 40, replace 40 with 55
any equation using 40, replace 40 with 55
what are the steps in using the formula method?
-establish unmasked threshold of TE -present masking noise at a level within the range of minimum and maximum to the NTE -re-measure the threshold of the TE, this is your masked threshold
if you have a type B tymp, what can you probably expect?
air bone gaps
why is IA not used to determine when to mask for BC?
since IA for BC is 0
what are the steps in using the plateau method for air conduction?
-start with masker 10dB above AC threshold of NTE -if there’s a response, increase masker by 5dB, if no response, increase stimulus by 5dB -keep going until you get a response at the same stimulus level after raising the masker 3 times. This is your masked threshold
what are the pros and cons of the formula method?
-pro-don’t have to worry about changing the masking stimulus because the range between min and max masking is the same as the plateau region -cons-requires calculations
-pro-don’t have to worry about changing the masking stimulus because the range between min and max masking is the same as the plateau region -cons-requires calculations
what are the pros and cons of the plateau method?
-pro-don’t have to worry about changing the masking stimulus because the range between min and max masking is the same as the plateau region -cons-requires calculations
what are the pros and cons of the plateau method?
-pro-does not require calculations -cons-have to play with masking stimulus until you reach the plateau region and get 3 responses
when does the masking dilemma occur (not mathematically)
when it’s impossible to avoid over masking and so you can’t obtain masked AC or BC thresholds
in the masking dilemma, what happens?
an adequate level of masking noise will cross over and be heard by the test ear, since the masking noise presented exceeds the maximum masking level
OE only affects what?
bone conduction thresholds
what is the occlusion effect?
when an ear is covered by an earphone or plugged with an insert, it improves that ear’s BC response
why does the occlusion effect occur?
since there are several different routes for BC, when the ear is blocked, the inertial and osseotympanic BC signals cannot exit the ear via the ear canal and get stuck in the ear canal
how do we compensate for the OE?
by using additional masking for BC. 20dB more for 250Hz, 15dB more for 500Hz, and 5dB more for 1000Hz
when does the masking dilemma usually occur?
bilateral conductive HL
how can the masking dilemma be avoided (SOMETIMES). why?
by using inserts. due to greater interaural attenuation
what’s a subjective hint about when you might see a shadow curve?
when one patient says that one ear is worse than the other.
the higher the IA, the ______________
less often you have to mask
in masking dilemmas, the lowest _______________________________-
masking threshold is always over masking
the masking noises used in pure-tone audiometry are called what?
narrowband (NB) maskers
why is the IA of inserts larger than supra aural?
because of the surface area of the transducer and how much of the skull is exposed to the transducer. Supra aural HPs go over more surface area of the skull, thus vibrating the skull at a lower intensity
what is cross-hearing?
when the signal is delivered to the TE and it is audible to the NTE too
IA is the difference between what?
between the level of the test signal (by AC or BC) and the BC of the NTE
according to the textbook, initial masking level is what?
according to the textbook, initial masking level is what?
The initial masking level will do what to the AC and BC of the NTE?
raise them both by 10dBHL since the initial masking level is 10dB higher than the NTE threshold
if the masking noise is 80dB and the tone is 80dB, where are we in relation to the plateau?
at the very right end of the plateau
over-masking should never be a problem when the NTE has a
SNHL
Tip: When MASKING with BONE Conduction, start with the __ ear
poor
