Dhar chapter 3 Flashcards
pure tones
lowest level a person response to tonal stimulus. unlikely in nature. freq and amplitude.dB. use AC thresholds at a few freq to get average. based on psychometric methods (limits, etc).
why puretones?
provide info on type of hearing loss and quantify freq-specific threshold
inter-octvaes
if theres a 20dB difference add more freq on the audiogram.
why do we have pure tone rules?
- To standardized across clinic
- Makes sure that that’s how its done time after time after time. So if tess works at an oncology unit…shes has to know when hearing starts being effective because of chemo
why pure tone audiometry?
Its frequency specific
A system test, but not a part of the system test. (OAE’s are part of the system tests. Outer ear etc)
speech perception in noise test
• But theres a better system test. A speech perception in noise test. Why not do this? Cuz it invalidates the frequency specific. Why does it have to be frequency specific tho? It tells us about the type of hearing loss and it’s a clue into whats happening. Not only is our auditory system organized by pure tone frequency, but also specific insults have effects. Being freq. specific in a certain test tells us where the problem might be…but can also tell us how we got the prob to begin with…the cause. Etiology.
Should we still worry about all of these frequencies and also worry about AC and BC? Why cant we do 500, 2000, and 8000?
It leaves too many holes in the puzzle. The pathologies that were after, have a finer issue than a broad scale. The resolution of the test has to be fine enough to catch the majority of diseases/pathologies. If they majority of brain tumors are half a mm in diameter, what good is an imaging test that only goes down to 2mms.
AC vs BC?
• Test different parts of the hearing system. Unique situation where you can test the same function using 2 pathways. Outer and middle ear, or not. And therefore by comparing the outcome when you test the same system using 2 diff pathways, you can narrow down where the problem might have occurred.
Should audiologist be doing pure tones?
• What parameters do you test on the fly? Masking. Could a computer do it and call u to come in? maybe. What other situations do u change? You could tell if they’re guessing. Could u train a high school student to tell u that though? Yeah. Any other objections? The whole process of diagnosing the patient goes from history counseling. AUD’s are the best at doing this…but john Hopkins doctors don’t drive to champaign to give me my xray specifically. What are you paying the audiologist to do? A secretary/assistant might not know if they’re faking the problem or not. AUD is technically paid to interpret, maybe otoscope, counsel; talk about treatment options, sumit doesn’t see AUD’s running health tests. What’s the most efficient use of your time? Routine cases why not have an assistant? If the cases are complicated an AUD could step in. This only works when you have enough patients.
-Important issues you have to control for when you do a pure tone audiogram.
- Don’t get the instructions. There is no standard way across the board. You have to redo instructions sometimes to make sure that you’re getting the best results possible.
- Equipment problems
- Cognitive capacity of the patient
- visual cues
Equipment problems
Headphones. Do we all use the same headphones..no. Notice audiometers don’t say which types to use. So even tho there is choice, the choice is limited because you want some kind of standard of how this is administered. Yeah you’ll couple it/calibrate it…so why does it matter? Youre gonna calibrate in a 2cc coupler (insert phones) and measure it. That 2cc coupler isn’t a specific ear canal..its some kind of an average representation. The average rep has been made by determining how far the ER3’s go into the ear. The iphone headphones don’t go in as far so the 2cc coupler isn’t the same anymore. You also cannot account for the distortion. The dollar store cheap earphones don’t only put out the freq you want to put out. So you raise your hand everytime because you hear all sorts of other freq too. Earphones are CRITICAL to standardized test results. ER3’s, TBH39, bone conductor thing and speakers also have a calibration and need to not distort. Over the ear earphones might not work cuz of collapsed ear canal. The cartilage isn’t as robust anymore so when u push on the pinna it distorts the volume. So some old people get a hearing loss when you put those headphones on. You have to be careful about placement. If the headphones don’t sit on the ear right…then the calibration doesn’t equal the right thing. Some of the sound could also leak out if the ear isn’t covered. Theres figure in the textbook (3f) that has audiograms that came from different people with different amounts of occlusion. You approach 0 at 80% occlusion and other than that youre thresholds go down cuz it leaks. If you place the BC vibrator anywhere..but your calibration is based on vibes made off the mastoid. So Transducers can influence test results
test tone
The rhythm….dont do it! If the subject has tinnitus then they might not recognized the freq/causes problem you use a pulsing tone or narrowband. Worbal tone? A freq modulated tone…the freq fluctuates around 1000 hz instead of just the 1 at 1000hz. U use this in sound field/with kids. It prevents standing waves/canceling out. The wave is never constant with a worbal tone.
• BC thresholds effected by vibrator placement
Its hard to keep it on the mastoid and not touching the pinna and without a bunch of hair under it and you don’t want it to be uncomfortable. An badly placed BC vibe has effects on results
compressional mode
compression of cochlear bony part makes basilar membrane move. bone is moving and then the cochlear duct is being compressed. Now if you have a balloon full of water then the water starts going back and forth. So essentially you compress the bony shell and move a traveling wave thru cochlea.
internal mode
You also have 3 bones in the middle ear space. Now we have an earthquake!! The whole “room” is moving back and forth. These bones tho move independently (like having a pic hanging in the house) and have a different rate of motion than the overall earthquake. So the combo of all of this sets up a 2nd mode of hearing.
