Pta Flashcards
What is the normal range of hearing in pta?
0 to 20db
What does AC mean?
air conduction
what is occlusion effect and what type of testing does it improve? and particularly at what frequencies?
The perceived increase of a bone-conducted signal reaching the cochlea when the external ear canal is closed, covered or plugged, e.g. by an earphone, thereby forming an enclosed air volume in the canal. The effect is greatest at low frequencies such as 500hz cana be as high as 20db
what is carhart effect and what does it affect?
A phenomenon observed in hearing by bone conduction in the presence of a conductive lesion in the middle ear; it is most often seen in cases of otosclerosis. The effect is observed as a depression (worsening) in the bone-conduction audiogram, maximally around 15 dB at 2 kHz; this audiometric configuration is known as the Carhart notch.
The Carhart effect is due to the fact that a middle-ear lesion not only attenuates signals in the normal air-conduction pathway but also affects the transmission of bone-conducted signals to the cochlea. The result is that the observed air-bone gap in such cases underestimates the true attenuation in the air-conduction pathway.
Name some of the transducer issues and what it can it result to? and what can you do to prevent it?
- Air bone- radiation of BC= when testing BC at high frequencies can result to sound leaking to the none test ear in which can result a better BC therefore it is important to occlude the none test ear at high freq and similarly, with BC at low freq testing it is important not to occlude the none test ear as this would result a higher BC result due to occlusion. This can cause a AIR-BONE GAP in which suggests a false conductive HL
- with AC collapsed headphones on the external ear cn cause an occlusion in which can result a lower high freq and which implies an improved BC therefore implying a false CL , therefore to avoid this its ideal to use insert as it’s less and to check if the ear phone is collapsed then prevent this by looking at the person ear canal and put some pressure on their anti tragus to see if the ear canal collapses and if that happens got to make sure that doesn’t happen.
what are the BSA classification for HL?
Mild hearing loss- 20-40
moderate hearing loss- 41-70
severe HL- 71-95
Profound HL- >95
What is cross hearing?
when the test tone can stimulate the non test cochlea therefore causing an unwanted response.
How does cross hearing complicates AC and BC
AC- is HL worst then it appears
BC- still don’t know what type of HL it is
What are the IA values on Transducer and Freq and what are the limitation of it
Largest is Inserts 55, super aural= 40 and Bone= 0 but possibly 20
freq= AC= SMALLEST MID FREQ, BC= smallest at low freq
limitation of the study=sample size was small and studies havn’t directly answered question about where to set criterion.
Name the 3 rules of masking and explain how it’s done and what is the reasoning behind it?
Rule 1 and 3= focuses on AC masking that asks the- is there is a HL and how bad is it? implication it could result the worst ear to look better then it is.
Rule 1- if there is a 40db difference between the two ears at each frequency. for example at 1khz there is a difference of the right ear of 40db ( if using supras) compared to the left ear. therefore, we have to use BC on the worst ear thus would be the left ear.
Rule3= if there is difference of 40db on the BC compared to the worst AC. REASONING BEHIND IT= that the non test choclea could be sensitive enough to detect the tone= (shadow response).
In order to test that, you need to know what transducer you using such as supra IA (40db) and see how much the sound could reach to the opposite ear. if its enough then masking needs to be conducted.
Rule 2 focuses on BC=
the rule is if there is a gap of 15 db of the BC AND AC.
Implication= it may appear a conductive HL but could be a SNHL.
What do you do? if there is a gap then mask it and if there is not a gap then that’s a true threshold of that ear but don’t forget about the other ear, therefore need to mask that as well, to get a true threshold of that ear, as that might be worst then it appears.
What is Masking?
Masking it when the non test ear is presented a noise (narrow band noise) to raise the true threshold of the test ear
What is a plateau?
Plateua is when the noise (non test ear) is not contributing anything more to the sound of the test ear
What is the slope of the directional peripheral masking?
The slope should be 45 degrees and 10db increase, this will demonstrate that a 10db increase of masking noise would raise the threshold of the test ear by 10db more,
What is central masking? and how do you know that’s the case?
That is when the noise and sound is processing higher then the perhial ear but to the CNS, therefore, the noise is gong to the non test ear and the test tone is going to the test ear.
the way you know this by the slope being less then 45 degrees and the raised threshold would be 5db
What is cross masking? and how is this a problem?
Cross masking is when the noise in the none test ear is loud enough to cross over to the test tone. The slope for this is less then 45 degrees and a 5db increase of threshold. Cross masking can cause a masking Dilema, especially people with a HL in the none test ear, that is the masker is already above the threshold of the none test ear.
