I’m not sure what you’re asking, but it sounds like it is going to oppozite way from what I would expect, which I cannot explain.
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Residual volume different venting/leakage. Not everyone tests with inserts either.
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On the audiogram side, you mean? You’d think they’d catch it with bone conduction?
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Yes, you’d think so, but BC is increasingly being ignored. Especially with the drive towards OTC aids - the added complexity doesn’t fit with streamlining the fitting process.
That left audiogram has all the characteristics of a basilar membrane with potential dead-spots.
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Ugh. That goes against my general optimistic view of the world.
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Mine too, it’s a dilution of the process.
It promotes the average, when we ought to be aiming to get the exceptional from the best technology.
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From the discussion above :
Observation: Insitu with a closed domes gives better results for low frequencies than audiogram
Apparent Logic : Closed domes helped in preventing leakage of low frequency sound. (The real low frequency threshold is then closer to the insitu one)
Question for professionals : Doesn’t it make the conventional audio-gram less reliable for low frequencies? Are the low frequency threshold differences between audio-gram conducted with headphones and ear canal sealing ear plugs considered / corrected in general?
:
I did my insitu using power tool kinda earmuffs over the aids and ears. Like the big old style headphones. I use open domes.
I saw some improvement in the higher frequencies because I could take my time deciding at what volume level I could hear the tone what with my tinnitus getting in the way.
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Those things aren’t related, the basilar membrane is in the cochlear. High frequency dead spots are easy to spot as they tend to occur at points of significant noise trauma (@4KHz for example). Low frequency dead spots are much harder to determine as the hair cell responses overlap each other to a much greater extent.
@Neville was suggesting that if you’d provided a BC result it would have identified the variability in the level being from a mixed (partially conductive) loss. Whilst my original assertion was that it was a test/leak error as there was no indication whether inserts (vs headset) were used. The other suggestion of the LF dead-spot is that testing variation can occur depending on the LF overlap and it yields a pretty similar reverse notched audiogram, which doesn’t respond to the ‘classic’ prescriptive gain models very well - simply because the Audiogram is a poor representation of the underlying loss: you’re almost better programming the aid to a flat 40-50dB loss with a REM/Live speech window open and just dialling up the sound manually while talking and providing a few noise stimuli.
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We do all our testing with inserts anyway. Closed domes can be flawed due to pressure on insertion issues or leakage in tall narrow canals.
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Does this imply that any PTA done without inserts potentially does have a risk of erroneous readings for lower frequencies?
There’s greater variation especially in the lower pitches when you use a headset. The assumed volume is around 5cc though that’s hugely variable, the clamping force will alter for different heads and some ears just don’t seal as well due to harder cartilage and voids in the skull shape.
Inserts aren’t perfect, but they do eliminate lots of sources of error.
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Thankyou @Um_bongo and @Neville this discussion has helped me understand the inconsistency of AC at low frequencies better
I ran the In Situ yesterday and applied the changes. I like the results. I am a little concerned at how much worse my low frequencies tested.
I would hate to think my low frequency hearing deteriorated that much since last February. Can I take it from reading this thread that it is normal for low frequencies to be worse when using In Situ?
That’s meaningless without a BC figure - looking at it, either the loss has worsened or you’re testing under different venting conditions.
However, if you find the result more beneficial, you might be headed the right way WRT actual adjustment of the aids.
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The original audiogram (grey) was done in a booth with headphones only. The In-Situ (red & blue) was done with with power domes in my family room.
I know the power domes leak because I have elongated ear openings caused by swimmers ear and they don’t cause occlusion. They do reduce feedback over bass domes though.
The audi did do BC testing for a couple of frequencies when she did the hearing test. She didn’t bother to document any readings because she said there was no problem.
I guess from what you’re saying, I will need to another hearing test done to find out for sure.
From Nov. 2009 to Feb. 2018 : I had a loss of 15 decible in the 250 & 500 frequencies. It would be worrisome to find I have another 15 decible loss in those same frequencies over a 9 month period.
I think it is the venting conditions that are responsible for the differences. I switched my 8 mm power domes with 6 mm double vent bass domes and ran the In-Situ Audiometry again. My results were even more varied in the low frequencies this time.
Note: I was wearing 6 mm double vent bass domes and still had power domes selected in Acoustics when I ran this In-Situ test.
I ran another test ( see my post below) where I have the same Base Domes selected in Acoustics and on the hearing aids prior to running In-Situ.
Choose exactly the same acoustic fitting in software before starting the insitu that you are actually using. Do the readings change when you change different types of domes and molds in the acoustics option of the software before running the test? If yes then the software is probably giving you improved results if you tell the software that you are using double vented but actually using a closed mold. Do share your findings
Ran the In-Situ again. This time with the Double Bass Dome selected. I did get slightly better results from having the correct domes selected prior to running In-Situ Audiometry.
I did the reverse. I was actually using Double Vented Base Domes, but still had Power Domes selected in Acoustics.
Note: The reading of 50 at 125 is wrong. The software wouldn’t let me increase to a db HL where I could hear the tone.
This might imply that software generates interpolated tones for lower frequencies . It might not be the real decibels but the equivalent decibels for the acoustic fitting selected. Do check again with double vent selected in software and the most occluding actual fit you can do (closed custom mold would be ideal but even power domes should do). I suspect it might take your results closer to the original audio gram .