Feedback and dome size

Hearing Aids
#1

Since my aids have got to full power I’m experiencing a bit of feedback, mainly if I put my hands near my ear. When I went to the audi she showed me the graph and there was a good distance between. She kept turning the aids down and I was getting less feedback but she couldn’t understand why I was getting any feedback with the graph showing OK.
Then she decided that the dome was too small and changed it. I had a lot of trouble getting it in and it felt uncomfortable but it did stop the feedback. Having worn it for a couple of days it was just too uncomfortable so I went back to the small dome and decided to live with it.
My question is it seems the dome is too small and it’s letting noise in. What do people do if they have open domes as they must let even more noise create feedback?

I am still getting unacceptable wind noise so she took some bass off, on the advice of Phonak who she phoned up! This has resulted in my television sounding like a cheap transistor radio and don’t even ask about streaming!

Overall I’m very happy to be hearing as well as I am, it’s a revelation but these niggling faults are taking the edge off. Am I expecting too much?

#2

Custom ear molds can help with feedback. Just from personal experience, I have custom molds with high power receivers embedded in the molds, small vents, and have virtually no feedback.

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#3

The Signia/Rextons have oval shaped sleeves that come in 4 sizes. They tend to fit better and prevent feedback a little better. However, they are not a cure all for feedback.

I would expect the Phonak software has a separate equalization setup for streaming. You should ask about it, to get the bass increased. It does not change the bass overall, just for streaming.

And there is always the option of custom molds. In theory they work the best. Your high frequency loss would suggest the need for molds. However my first pair is certainly not nirvana by any means. Going in for a second try next week.

The Connexx software suggest feedback problems with your loss and a NAL-NL2 prescription. See this graph the soft sounds for both ears go into the shaded feedback zones.

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This is what custom molds look like with the recommended vent size. Same gain and no predicted feedback. However keep in mind that my molds to date have not performed as well as the computer predicts. YMMV!

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#4

Thanks for your detailed reply.
I have got tulip shaped domes already and I do find the smaller ones comfortable.
The odd thing about the graph she showed me was there was no overlap into the shaded area which was why she thought I shouldn’t get feedback.
It really isn’t a deal breaker, I’m more irritated by the wind noise! I can see me buying a pair of the ear gear protectors.

#5

There are two ways that I know of where they can generate a graph showing feedback potential. One is a simple prediction based on statistical data they have collected. That is what is in the graphs I gave you. The other way is to do what Connexx calls a Critical Gain Test. That actually generates noise and tones to test for feedback, and produces a similar graph except that it is based on your situation. That would be more accurate. There is actually a setting where they can allow the software to intrude I think 5 dB into the shaded area, or not at all. If the area is avoided you just lose the gain and associated hearing benefit.

I have accepted that wind noise is a fact of life with hearing aids. In mild winds the wind noise reduction seems to work. In stronger winds it is simply awful, and I just mute them until I can get inside.

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#6

I was having problems with feedback and discovered the major cause was earwax build up in the ears. I had them syringed and the feedback completely disappeared. Just a thought.

#7

I don’t generate much wax. The audi had a look yesterday and they were fine.

#8

Suggest using custom ear molds and have your audiologist restore the settings to normal and you will have what you were expecting from your aids! Have never had feedback since using custom ear molds.

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#9

Sierra: I have accepted that wind noise is a fact of life with hearing aids… In stronger winds it is simply awful, and I just mute them until I can get inside.

Can I ask further about this statement? Awful as in, conversation is a complete impossibility?

This is what I have found even with a modest breeze and it drives me crazy. It’s something, for the past month since I first started wearing HA, I’ve been working with my audi to try and make sound more natural. If this isn’t something that can be adjusted/resolved for anyone, then I’m going to need to adjust my expectations of what happens when wearing my HA.

#10

I think that you mean the LOUD sounds. If Connexx software is like ReSound’s, there is the odd feature that the gain table below the fitting graph, the rows run from soft to medium to loud but in the fitting graph, it’s the reverse. Soft sounds are lowest, medium higher, and loud highest. And if like ReSound’s the solid red line (right ear) or solid blue-green line (left ear for Connexx-ReSound uses a solid red line for both ears) is the MPO with the given receiver power.

I agree that AllanH should have his audi do an active feedback test. That’s what I’ve had done with my domes and molds and the results clearly show the domes in my ears don’t seal well, the molds do and as Scotty_G says, virtually no feedback problems since getting custom-fitted molds and wearing them with occlusive venting (which I’ve chosen for other reasons).

The following graphics illustrate reduction in feedback zones on switching to molds (graph on right) with the lighter gray areas coming down from the top of the graph being areas with the potential for feedback if amplification enters those regions. Self Fitting Resound Quattro 9s

The following post has fitting graphs and gain tables for ReSound illustrating that the relative order of soft, medium, loud is reversed in presentation between the two depictions. The solid red line at the top of each graph is the MPO (maximum power output) the receiver is capable of at a given frequency: One Provider's View on the A, B, C's of Fitting and Dealing with Basic Fit Problems

#11

Yes, I would think conversation would be next to impossible. My hearing is still reasonable without HA’s, so I think I would simply remove them. In a brisk wind my HA’s sound like somebody blowing as hard as they could into a PA system microphone. Brutal, even though the Wind Noise reduction is set at max.

#12

I am self taught, so I could have it all backwards. However I thought the same as you, and recall someone here correcting me. Here is another clip that shows the the numbers. Also when I mouse over the curves the top curve says Target 50 dB, Middle is 65 dB, and bottom is 80 dB. That makes sense to me for compression. Loud sounds get amplified less. Also I think it is insertion gain that causes feedback. If the mics are hearing the same sound level as the receivers are putting out, feedback is unlikely even if that sound is really loud. However if the receivers are putting out a large relative amount even if the source sound is low, that can start feedback. At least that is the way I have rationalized it…

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#13

I think you’re right that I’m making the same beginner’s mistake that you formerly did. For my HA’s, there are two views, GAIN vs. FREQUENCY and TOTAL OUTPUT (input plus gain) vs. FREQUENCY. It’s in the latter where the LOUD total output sound shows up on top, the SOFT at the bottom of the graph, the reverse of the gain table. But when one looks at dB GAIN applied vs. FREQUENCY, as you say, the SOFT sounds are at the top of the graph because they have more gain applied to compensate for hearing loss and make them loud enough to be heard. And LOUD sounds have the least gain applied because one can probably already hear them unless one has severe to profound loss. And the whole overall effect is to squeeze the normal range of sound into whatever limited moderate to loud range of sound at which you can still hear (compression).

I also looked at Dillon’s HA book and he agrees with the advice given you that it’s the softer sounds with greater gain that usually cause feedback or else the user having the volume of his/her HA’s cranked up too much - I guess turning up the volume adds gain to all sound levels from soft to loud! He says basically that feedback occurs when the gain added to a sound exceeds the attenuation of sound in the ear canal path from receiver back to HA mics so when ever there is thus a net gain of dB on a round trip, you can get positive feedback if there is also the right phase relationship between incoming sound and fedback sound - out of phase between the two, you can actually get some cancellation, negative feedback instead. I guess feedback usually occurs in the 3 to 4 kHz region as that is around the resonant frequency of the ear canal (least attenuation of sound on round-tripping) and also the most amplification is usually applied in that region to compensate for hearing loss.

#14

I had a lot of feedback with Widex Open domes (size L) and switched them out for Widex Round domes (Size M)
No more feedback!
I believe they fit Phonac’s as well.
Here is the website, ask your Audi to test their different styles or purchase them at Amazon.

https://www.widex.pro/en/products/accessories/easywear-wired-ric-ear-tip-solution

#15

I never have undersyood why people think off-the-shelf domes/molds will be optimum way to go. You buy custom fitted prescription eye glasses. After spending well into 4 figures for HA, why not spend $50-$100 to get a correct fit?

#16

@AllanH what type of Phonak aids do you have? As some Phonak models do have a wind block feature where the aud activates it and it cuts out all wind noise. I’m not sure if yours does though.

Feedback is from poor fitting domes. If your now needing more power you probably would benefit from a custom fit mold with a small vent. I found the Phonak tulip domes to be very uncomfortable that my aud fitted the Oticon domes on my Phonak aids. Not really the accepted thing as far as the companies are concerned but if its a comfortable fit I don"t much care.

#17

I have tried open sleeves, closed sleeves, and now a custom mold. So far, the best results have been with the off the shelf closed sleeves. I am now waiting to get new impressions made for a third try at the custom molds. I believe it is all in the fit. If you get a good fit with an off the shelf product, you are golden. If you don’t get a good fit, even with molds, the problem remains. I believe it is an issue of how close your particular ear canal is to what the off the shelf product is designed for.

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#18

I’ve got the Phonak M90. She did say that the windblock is all the way up so there’s nothing left to do. Makes me laugh as they boast how much better the microphone design and placement is on these aids, the older aids must have been diabolical.
I would have expected the sound to at least lessen when it is encountered but I hear no difference at all, maybe I’m expecting too much.

#19

Brilliant! Thank you! Although I did the reverse and got Phonak power domes on my Oticons. The feedback manager warble is still there, however, we were able to put much more power through which is great!

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