Questions about Earmold Types and Venting to Reduce Feedback



I have had Kirkland Signature 8.0 HA’s for about 3 months now. The right one has always worked quite well and the left one not so good. The loss is significantly worse on the left. I started out with vented sleeves in both ears, then tried unvented sleeves in both ears. The issue of what appears to be feedback around 3-4 kHz at higher ambient noise levels and high amplification levels remains in the left ear. I use the Own Voice Processing feature of the HA’s and do not find the occlusion effect with the closed sleeves that bad. Not an issue for me. My left HA has the gain tweaked back some from the REM gain that is said to be ideal. This is to make them tolerable to use with the feedback minimized.


From some research I see that the vented sleeves have two vents that are said to be equal to >4 mm diameter x 16 mm long. The closed sleeves are not really closed and have a single vent which is .8 mm x 4 mm and said to be equivalent to a 1.6 mm x 16 mm vent.

The Connexx software which I have installed says that I need a Click Mold Short in these sizes:

Right Ear: 2.5 mm = medium SAV
Left Ear: 1.3 mm

Some Questions:

  1. What is calculated for a vent in the Left ear seems to be larger than what I currently have in my closed click sleeve if it is not 16 mm long. True, or is it really 16mm? Is it going to help or hurt with feedback?
  2. Should I get an earmold in just the left or both ears?
  3. What material should I get? I have read that the softer silicone offers the most acoustic isolation.
  4. What type of earmold would be best? Canal lock or ??

Thanks for any help you can provide. I am getting a bit tired of all of these changes and fittings, and would like to get it right this time…

Edit: I should clarify that I am not asking this so I can tell the fitter what to do. I am just assuming there may be options in what she can do, and I want to be able to select the best ones.



Since you’re experimenting, I think I’d go with the Select-a-Vent that @jim_lewis chose. Have you considered asking them to test you for dead regions? It’s possible that no amount of gain is going to help you at certain frequencies.



Thanks for the comment. I will ask if Select-a-Vent is an option. I see that this company in Canada called Emsee Labs that makes earmolds has the Select-a-Vent option, but it apparantly can only be installed if there is room. I am using small click sleeves, so I don’t know if that will be the case for me.

I have done some home testing and verified I can hear all frequencies up to 8 kHz with my left year with enough amplification. And, I do not hear any noise or buzzing along with the test tones, just a very reduced volume. So, I don’t suspect there are real dead zones, just very reduced response. What I am hearing with the HA’s at higher sound levels is just added crap/noise on top of the real signal. While I was resistant to admit it initially, I am coming to the conclusion that it is simply feedback. That is what the fitter thinks as well when I describe what I hear.



You may very well be on the right track, but I’m a doubting Thomas. Have you considered you could be hearing the tone in your other ear via bone conduction? Clearly I’m just speculating.



I’ve forgotten what your Connexx fitting profile looks like with any feedback sensitivity region displayed. For me, I found the most useful curve was the feedback analysis curve provided by ReSound’s Smart Fit software. It showed, for example, that even with an “oversized” tulip dome or a power dome crammed into my ear canal that, because of the irregularities in the shape of the canal that one is trying to occlude with a pretty regularly-shaped device, the inexpensive, off-the-shelf domes were just not allowing me to control occlusion to whatever degree that I wanted. As expected, when I switched to custom-made molds by inserting a solid vent insert, if I wanted, I can get almost 100% complete occlusion. One of my ear canals is very small and it requires a pretty small mold that just accommodates the receiver and the vent tube. I know some users have mentioned getting their custom molds with money-back guarantees - maybe they were already paying a provider for the full retail package? - but I wonder if your provider could tell just from inspection or just making an impression (hopefully cheaper than completing the deal with a mold) whether your ear canal will accept a suitably sized mold made to use select-a-vent?

See Smart Fitting curves towards the bottom of the following post. The light gray shaded area descending from the top of each graph shows the region sensitive to feedback (hence the lack of occlusion) below the amplification max limit for the receiver in use (MP in my instance) (lower limit of top pinkish red region).

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As my audiogram shows, my hearing is pretty poor. I have tried various ear tips over several years and ended up using these:Capture
They are cheap, comfortable, and I have no feedback after gently pressing them into my ear canals probably eight or ten times a day.



i.e., you put them on the receiver wires, behind the domes, and push them into your ear canals after inserting the receivers fitted with domes?



Users that have profound hearing loss should use unvented full shell ear molds.
Good ear vented ear mold
Bad ear unvented ear mold.



“i.e., you put them on the receiver wires, behind the domes, and push them into your ear canals after inserting the receivers fitted with domes?”



I think that’s not unreasonable advice for OP, but not generically for somebody with his loss. He only has a slight to mild loss out to 1500 hz.



I have moderate sloping to profound loss and use a select-a-vent mold. I use the smallest vent and I get no feedback and no occlusion.

About software changes, reducing the gain would be third on my list and should be avoided unless there is no other way, and usually there is another way.

With a combination of the feedback control processing, and changes to the fit, feedback can be controlled. I would go with maxed out feedback processing, to handle 1 second of feedback, rather than turn down the gain for 24 hours.



I am still trying to piece together some of the research I have done. I recall one report that I read concluded that only the part of the earmold that was in your ear canal provided effective sound isolation. The part in the outer ear did not. I also recall another article claiming that a soft mold was no better than a hard mold, as it is the ear that gives and accommodates the mold, not the other way around. Then there are reports that silicone and silicone II give the best isolation. Somewhat confusing at this point…



The way the Connexx software seems to work is that you need to run a test to determine critical gain to see the area at risk of feedback. To do that one needs a connection to the hearing aids which I do not have. I just run the software in simulation mode. At my request the fitter has done the test, and the image below is my recreation with a yellow highlighter tool of what I recall seeing. Essentially the risk was not encroaching on the prescribed correction for my right ear, but it was on the left.



That is an interesting idea. Makes me wonder if I could make something like that from some safety ear plug material…



Even though it doesn’t seem to be encroaching on the right, that’s only under 80 db SPL input, probably. So I bet for loud noises in the resonant 4K max sensitivity region that you can get feedback in the right ear as well, too. With my open domes, even though the feedback analysis region didn’t overlap the maximum output shown for 80 dB input in the graphs I linked in a post above, I could still get feedback.



So in other words, it would be better to go with earmolds in both ears?



Audiologists have told me over many years that the full shell earmolds are the best way. I did have soft earmolds that sticks better to the ear but sometimes give me an ear rash. I had a custom earmold that the cone part was soft material and the outer shell was hard material. Nowadays l have been told that nobody makes that kind of custom soft/hard earmold anymore.



I just got off the phone with Lloyd’s about my my new earmolds getting made. They needed to know what size vents to put in. The Target software calls for .6-.8mm vents with earmolds. I asked about select-a-vent. I believe he said the smallest size mm with select-a-vent was 3mm. I may have misunderstood him but that’s way too big for my loss. We decided to go with 1.0mm vents and soft silicone canal with lock molds, not half shell or full shell. They will be in the mail today. Cost a little over $100 for the pair. These earmolds will be on Naida UP aids with power slim tubes.
I have been trying different domes and tulips with bad results. No feedback issues just not enough power, lack of clarity.
Hopefully this may help you go in the right direction.



The trouble with “select-a-vent” is that the range of vent sizes might vary depending on what mold manufacturer you get. With ReSound, besides no vent, the smallest size insert vent hole was in the 0.5 to 0.8 mm diameter range (hard to measure something that small). And no packaging information as to where the vent insert plugs came from, if I want to get more for some reason-guess it’s back to my audi for more, if needed. The holes for the vent inserts to go in the left and the right molds were different sizes because the left mold had to be smaller due to the smaller diameter of my left ear canal and, strangely enough, the smallest size vent holes in the different-sized plug inserts for left and right ear were different - maybe because of the difference in overall shapes for left and right ear molds required different-sized vent holes for equivalent acoustic resistance? The larger and smaller plug inserts with the different sized holes came on the same “tree” of inserts, though. I didn’t ask my audi what it was all about - I just chose the closest sized holes to match for left and right plug inserts. Some of the inserts for whatever reason seemed prone to plopping out of the mold tube holes - the smaller sized insert plugs with bigger diameter vent holes were a bit on the floppy side and did not seem to grab onto the side of the mold bore hole as well as the more rigid insert plugs with smaller diameter vent holes, etc.



That sounds pretty much like what Lloyd’s was saying too. That’s why we went with the 1.0mm straight up. Lloyd’s mentioned plugging issues with such small vents.
The OP sounds a little like me concerning not quite right fitment. My many different dome trail and errors led me to going ahead and doing earmolds. When your loss gets to a point of bad word recognition you have to do something. Hopefully the earmolds will help with all the frustration.