Feedback from full shell earmold

#1

I had a full shell earmold made. Well, I have been wearing it for a bit, and I sometimes hear feedback in my ear that others cannot hear because I asked. I am so annoyed at this. What is wrong with the earmold doing this? Do I need to go back?

I don’t know if earmolds have changed the past few years, but it has a “second” tube to the side of the earmold that goes in your ear. What the heck is that for if you know what I am talking about? Also, I noticed that the tubing does not go all the way to the edge or flush to the inner part that goes in your ear. Could that be an issue for whistling?

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#2

What type of hearing aid do you have? A behind the ear (BTE) with a tube going to the earmold? Or is it a receiver in the canal (RIC) type? Or is the whole hearing aid in the ear (ITE)?

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#3

BTE with tube and a full shell

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#4

Basically feedback is when the sound from the HA receiver (speaker) makes its way back to the HA microphone. In a BTE the sound would have to come from the speaker, go down the tube, into the ear canal and then go back to the speaker. It generally can go one of two ways. One is simply through the vent, which most molds will have. The other can be leaks around the mold if the mold does not fit well, of if the fit changes when you move your jaw or talk. Is there any pattern to when you hear the feedback? That might be a clue.

I recently had molds made and they have been less than satisfactory. They were done with a relaxed jaw while the material setup. The next set which I am waiting for was done with an open jaw, which I hope will fit better. They are silicone which is claimed to be better for feedback. Mine are a simple canal type.

I did a bit of research on these things and one of the claims I found was that the true sealing was done in the ear canal, not in the outer ear. If the mold does not seal in the ear, the the outer half shell will not stop it from getting back to the microphones.

I’m not sure what to make of your description of an additional tube. I had saved a link to this Starkey Guide to Earmolds and they talk about a power vent, which sounds like a tube on the end of the vent which is supposedly routed to suppress feedback. See page 10 of this guide.

The other issue besides fit and lack of sealing is that the vent is too large. Generally the larger your loss at 3-4 kHz the smaller the vent has to be to prevent feedback.

But to answer your question, if you have feedback then go back for resolution. I got mine at Costco and they claim they will remake them as many times as necessary to get them right.

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#5

The ‘second’ tube you are referring to is likely to be a vent. That’s what I have as well with my ear moulds. It helps with occlusion and hearing aid performance.

Sometimes I get feedback, this can’t be helped for me as I have a lot of amplification. This only happens when I press my hands against my hearing aids, otherwise it doesn’t happen.

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#6

Maybe a Slect-a-vent.

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#7

One of mine supposedly has a SAV or Select a Vent. However, it is really hard to see. Just looks like a regular vent hole through the mold to me. There is nothing sticking out of the mold.

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#8

You may find this document helpful if you want to dig deeper into the subject of molds. It is by Starkey too.

Attenuation variables in earmolds for hearing protection devices

They are basically talking about hearing protection ear plugs, but my expectation would be that all the same issues apply to a hearing aid mold. You need them to seal, except for the controlled vent.

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#9

might wanna check for wax, I have that issue as well! (would be worth seeing an ENT if you have excessive earwax issues like me)

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#10

So, I think it is a vent. I don’t believe I have seen that before. I thought it might be something new in recent years. I have not worn a hearing aid in my other side, so it’s been about 5 years since my last ear mold. From the hole that goes in the ear canal, I can see two holes. I never saw that before. The tube would go all the way and be cut flush to the ear canal end of the ear mold if you know what I mean, so now I see inside it two holes. Very strange. I have never seen that before, and I thought it might be another new crap invention. Sometimes the older and simpler style is better. I will keep trying and read the document for info about this, but could I get one without it if I don’t think it’s working for me as I try it more? Today, I didn’t hear the feedback, but it was terrible yesterday. Sometimes when I opened my jaw, I’d hear it more. Very annoying.

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#11

Here is a link to the basic vent styles. The normal style is a parallel vent. The tube from your BTE aid goes down to the inside. Parallel to that is a vent which allows sound pressure in and out of the ear canal.

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#12

So my audiologist will decide which one I need? I am not quiet sure which one would be me based on the description lol. I don’t recall seeing this before, honestly… Maybe I have forgotten. There is a plug in the back. I am annoyed the audiologist don’t explain this to me. Maye it is so routine to them.

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#13

The critical parts are:

  1. The fit of the earmold in the ear canal. If you get feedback when you chew it would seem it is not a snug enough fit.
  2. The size of the vent has to be matched to your loss and the gain that is being used. Too large a vent for the gain will end up with feedback.
  3. The material is a more minor factor. Softer silicone may have a small advantage.
  4. The style of the mold is less important as long as it stays secure in your ear. A big full shell may not be helping you if the fit is not snug in the canal portion, or the vent size is wrong.

But, all this is really the fitter’s problem. Tell the fitter when you are getting feedback and they should be able to figure out what to do.

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