I have KS10 and self-program. The target gains are missed around 4KHz due to the feedback threshold limiting the gain. So I have added overtuning to raise the feedback threshold and allow more gain at these frequencies. I am currently testing this. See before and after snapshots attached.
My question is regarding what downsides there are to this (apart from the obvious increased risk of feedback) and if there are any alternative approaches. I have a 3mm vent in the cShells and would appreciate comments on whether that is too large for my loss and a smaller vent would be better.
Which approach is liley to be better for me (smaller vent vs overtuning)?
Why would you want that?
In my opinion, we should always strive to prevent feedback.
I once just closed the vents for a experiment. Then found I could live with the occlusion. The result was better on the bottom line: matching prescription, no feedback, better low frequencies in streaming, better speech comprehension in noise.
I’m curious what the more experienced members think about it.
I want it so I can get closer to target gain around 4KHz. Without the overtuning, the gain is limited by the feedback threshold. Having made this change, I haven’t noticed any additional feedback.
When I tried thin tubes and domes, the open dome reduced the gain by loads even tho my right ear said an open dome was fine. I changed to and now I can get the gain.
3mm vent is a rather big vent! If you have these feedback issues, I would suggest plugging them with silicone and drilling a hole. For experiment’s sake you could also use an plug made of an eraser. If you like the results, you could make it permanent with two-component epoxy resin and drilling. My audiologist used a UV hardening plastic to plug the hole and a rotary tool ( a.k.a. dremel ) for the drilling. (She needs the results fast, so she can help the next customer.)
EDIT: Another quick one for experimenting is electric wire shielding: The copper wires have 3mm outer diameter. (Inner diameter is ~1.2mm):
No feedback, just reduced gain at higher frequencies. Was just wondering if there are any benefits to overtuning over reducing the vent size. One benefit of overtuning is that I can do it (and undo it) easily via the software. Changing the vent is more tricky,especially as I am still trialling them.
Which approach is liley to be better for me (smaller vent vs overtuning)?
You definitely want a much smaller vent, don’t use overtuning, as @sterei has pointed out, feedback will be a problem at times, at your level of loss you should be a occlusive fitting for best results,(as your upto 100dB in some frequencys, this profound loss) this will lift the gain in the appropriate frequencies (and across the board, as you make adjustments in one frequency, this will change others as well)
One benefit of overtuning is that I can do it (and undo it) easily via the software. Changing the vent is more tricky,especially as I am still trialling them.
You can actually change the vent size in target and see/hear the changes in real time (just to experiment with results)
You can actually change the vent size in target and see/hear the changes in real time (just to experiment with results)
Happy to be corrected but I don’t think that is right. After removing overtuning, if I change the vent size in Target, I need to perform a new feedback test which is dependent on the physical characteristics of the ear/mold. Doing so will reset the feedback threshold back to the non-overtuned lower values and so maximum gain around 4KHz is reduced for me by about 12db. Setting it to “occluded” as an extreme case did not raise the feedback threshold. I don’t see how I can get increased gain at 4KHz without either overtuning or physically smaller vent and resetting threshold via feedback test.
I have not noticed any difference when choosing different vent sizes in the Target software. Am I missing something? Feedback Manager seems to be doing a good job of reducing/eliminating feedback even when overtuning is enabled.
But that does raise the question as to what the point of the vent size setting in the software is, apart from being a reminder to do the feedback test again or just for record purposes.
Just to say that I have had fully occluded moulds for several years, but latterly I found I preferred a vent, however small, as this allows for pressure changes in the ear canal and is more comfortable to wear without fiddling with them to equalise the pressure.
In any case, having said that, avoiding feedback is the top requirement in my mind.
That’s interesting, as I have always had vents. My current trial of the Phonak Paradise / KS10 started with very small vented molds. They didnt fit very well and occlusion was bad. I asked for the molds to be made to the same spec as my previous aids (Phonak Virto Q90s) and they came back with a 3mm vent, although I am sure the Q90s vent was not 3mm (see attached with KS10 on left).
@david.hendon, do you know what was done for you to avoid occlusion as your hearing loss is similar to mine?
In fact nothing was done to avoid occlusion. I just accepted it and it was the least of my concerns. But my hearing loss in my left ear was much worse then than it is now, as I had a stapedectomy operation on it in June 2021 and this made my two ears much more similar, as shown in my here.
Now I’m using power domes on HP receivers that are barely inserted into my ear canal and that works well with my new Resound Ones. I don’t get any feedback problems fortunately. My wife is quick to tell me if she hears a squeak!
When you change the vent size in Target, you have to recalculate the fitting to allow the change in venting.
The bigger the vent, the less low frequency gain you have in Target. Or at least, that what Target does to my Aids.
Occlusion issues, change the setting, the stronger the setting, the less low frequency gain you have.
EDIT - even tho you haven’t physically change the vent size, you can change the vent size in Target. As you haven’t physically changed the vent, no need to run Feedback test again.
But that does raise the question as to what the point of the vent size setting in the software is, apart from being a reminder to do the feedback test again or just for record purposes.
The size of the vents also affects the calculated gain curves:
Let’s say that according to your you need high gain in the highs and low gain in the lows (typical ski slope).
A large vent will allow the low frequencies to reach your ears without the need for amplification from the . The same is true for an open dome.
On the other hand, with a small vent or a , the low frequencies would not reach your ears, and the HAs has to amplify the low frequencies as well.
Therefore, the size of the opening is needed for the calculation.
However, before you perform the feedback test, you can check a box to decide whether the size of the vent should be estimated or not (checkbox). This means that the gains shall be calculated based on the feedback measurement or based on the vent size you entered.
If the vent size you entered is completely off the chart, the box checks itself automatically after the feedback test and the estimated vent size is used for the calculations.
This is how I explain it to myself, maybe I am wrong. If anyone has a better explanation, feel free to correct me.
The size of the vents also affects the calculated gain curves:
Let’s say that according to your audiogram you need high gain in the highs and low gain in the lows (typical ski slope).
A large vent will allow the low frequencies to reach your ears without the need for amplification from the HAs. The same is true for an open dome.
On the other hand, with a small vent or a closed dome, the low frequencies would not reach your ears, and the HAs has to amplify the low frequencies as well.
Therefore, the size of the opening is needed for the calculation.
However, before you perform the feedback test, you can check a box to decide whether the size of the vent should be estimated or not (checkbox). This means that the gains shall be calculated based on the feedback measurement or based on the vent size you entered.
If the vent size you entered is completely off the chart, the box checks itself automatically after the feedback test and the estimated vent size is used for the calculations.
Thanks @sterei. I did try recalculating the gain curves with extreme vent settings (open to occluded) and the box unticked, but for whatever reason it did not automatically check itself (at least for me in my situation). However, I can see what you say when the vent size is needed (whether it is estimated via test or taken as correct) to calulate the gain curve. And I do see changes in it when I recalculate with different vent sizes, although not huge and mostly in the lower frequencies.
It is my assumption then that any changes to the gain curve are minimal or less for higher frequencies. And it is at 4KHz that the feedback threshold is restricting possible gain. And the only way to regain the gain is by overtuning or smaller vent. But even when I set the vent to be the smallest possible, the feedback threshold change was negligible at the higher frequencies, but in reality I would have expected the feedback threshold to be higher at 4Khz for smaller vents.
Doing so will reset the feedback threshold back to the non-overtuned lower values
Yep, and why is this, this is because you are using a 3mm vent, this is inappropriate for your level of loss (no one uses 3mm for profound) I can say that you should be more like .8 or .9
do you know what was done for you to avoid occlusion
By having a smaller vent size fitted (more like .9 ) you can avoid the occlusion effect, and of course you want a tight fitting mold, BTY have you tried silicone ones? These work really well for profound users, but Phonak doesn’t offer them in c-shell, if that’s what you are using.
By having a smaller vent size fitted (more like .9 ) you can avoid the occlusion effect, and of course you want a tight fitting mold
I still have some receivers with a very small vent (They were what the first fitter suppplied for my orginal Phonak Paradise aids). They were a poor fit and so the occlusion was bad. I just replaced my 3mm vented molds with these 1mm vented molds to test. If I push the 1mm vented molds in, then yes I dont get occlusion, but as soon as I stop pushing them back in, the occlusion is unbearable. And when I did the recalc with the 1mm vented molds, there was still 5db between target gain and feedback threshold gain at 4Khz. But, this is better than the 12db I get with the 3mm vent.
The first fitter replaced the 1mm vented molds with 2mm vented molds but the occlusion issue did not resolve (they were still a poor fit). I am coming to the conclusion now that the poor fit was mainly responsible for the occlusion and not the vent size. SIGH.
My current aids ( Virto Q90) have a 2mm vent and good fit and no occlusion or feedback. The latest attempt to fix the issues resulted in a new mold which now fits well (pushing it in does not make any difference to sound or occlusion) but a 3mm vent (no idea why I got 3mm). And the 3mm vent is limiting the gain at the higher frequencies (unless I overtune) and do not experience feedback issues.
I have my next followup appointment in about 10 days. I will look to get a new mold with same physical dimensions to keep the good fit but with a smaller vent.
All the molds I have tried are acrylic. I have not tried silicone and yes, current ones are cshells. Do you know why a silicone mold would be better? I’ll have a look at what the alternatives to cshell are. I have no idea what option costco have available.
They were a poor fit and so the occlusion was bad.
This comment is confusing, usually you’d say they were a good fit (tight, no leakage from the mold) and this is why you had the “occlusion effect” but anyways as you have noticed, the bigger the vent the less occlusion(more feedback, less gain) so it’s just a matter of working out what’s best for you, 1mm is to small for you, so maybe 1.2mm /1.6mm could be where you go next, your audiologist can offer select a vent from Phonak (borrowed from @MDB) these are small soft plugs you can fit into the 3mm vent on your molds to reduce the size without having them remade straight away, just to test which size you prefer.
Check out the very latest Activevent from Phonak, I have no experience with these, but I think they could be something that could work in the future, if they could just boost the receiver limits to include severe loss. Best of both worlds? Maybe…
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As for silicone molds, they can be made oversized, so being soft they are sometimes a bit hard to fit in the canal, but get pretty easy over time to fit, plus being a really tight fit with no leakage, and while providing that tight fit, they are flexible, so will move with your jaw when chewing, but again it’s something that you’ll need to test to know if they are right for you, because of these characteristics they are a good choice for severe profound users.
This comment is confusing, usually you’d say they were a good fit (tight, no leakage from the mold) and this is why you had the “occlusion effect”
When I tried the 1mm vented molds, and kept them pushed in gently, there would be no occlusion. When I stopped pushing them in, my voice and everything else became boomy. My assumption was that the poor fit of the mold (it must move slightly when pushed gently) was responsible for the difference and if it was tighter and didn’t move, then the experience would be the same as when I pushed it in gently.
I was surprised how large the effect was as the movement of the mold when pushed was hardly noticeable. I am not sure I can explain that as I thought a tighter fit would INCREASE occlusion as there would be no leak (apart from through vent). But pushing it in gently REDUCED occlusion.
I would love to know of some rational explanation!
Select-a-vent sounds good in theory. For me the different sized vents would quickly slide out making them useless. The new ActiveVent sounds promising, but I have no idea how the cost or reliability is.
One challenge I’ve had with custom molds is getting them to stay in the same place. If they slide out slightly, it can increase the leak and cause feedback. I think a fair amount of trial and error (or luck) is involved.
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) this also has a major effect on gain curves.