Making a custom mold for receiver-in-canal (RIC) hearing aids

[Markismus]

As multiple threads led to the same question, I have taken a few photo’s whilst making custom molds for my RIC Phonak Audeo M90 aids. (I’ve posted about mold creation for BTE with slimwires for my Phonak Bolero B90’s a while back.)

The trouble with RIC’s for me is that the conventional way of stuffing 2-component silicone into your ear, waiting for it to harden and drilling a hole doesn’t work. My ear canals are too small and I can’t drill both an air vent and a hole for the receiver.
I have to put the silicone around a dome and the receiver and a plastic wire. After hardening I pull the wire out and I have a vent. The first results were not as brilliant as the slimwire custom molds. Especially, the lower frequencies kept escaping: The lower frequencies (<750Hz) were typically 10dB-15dB worse with the AudiogramDirect measurement. (With Power Dome 4.0 M I typically get values with AudiogramDirect that fluctuate around my audiogram.)

With my new receivers came new vented domes 4.0 in 3 sizes, which are differently shaped as the previous series. The largest are between 12.0-12.5 mm in diameter, the middle are between 9.0-9.5 mm and the smallest are about 7.5 mm. The dome at the most left is the smokey dome M of the previous series.

The largest dome is quite brilliant. My AudiogramDirect values were 5dB-10dB lower than my audiogram. However, on warm days in the last summer they ached. So I tried the medium dome and it is reasonably good (0-5dB lower values). However, the piano sounds off. So I need to make custom molds.

I measured 2x1.00g of two-component polyaddition silicone paste, I mixed it and made it into a thin role of about 2-3mm thickness.

Using the smallest dome ( 7.5 + 2 x 2.5 is about 12.5 ), I put a plastic wire into the vent and encircled it with a bit less than half of the roll.

I repeated that with the right receiver, pulled my ear up and put them up my ear canal. This is the result:

I cut off a large enough amount, so that the receiver sticks out and I can get a grip on it. Gently put a knife against the receiver and rotate the mold will do the trick. After that I removed the old receivers and inserted the ones that I use:

The result: The piano sounds good! The molds are not as solid anymore. Without domes for the BTE slimtubes and with the smokey domes (see picture 1 at the utter right) you get a solid plug that is put into the canal. With these vented domes 4.0 S, some of the elasticity or bouncy-ness remains as the hollow core remains hollow. I expect that with the vented domes 4.0 M, the bounce will be more pronounced. For me that is very nice, as my ear canals expand after the entry and instead of plugging the entry, I rather have a balloon that blocks it from inside the canal.

During the mold making, I found that a lot of the silicone was pushed away from the dome onto the receiver while the whole thing went through the smallish entry of my ear canal. Still, a lot remains on the domes.
Also, with power receivers the smallest dome fits very snugly around the receiver. Given some earwax, I don’t think they’ll vent anymore.
So I am going to order medium domes and repeat the experiment.

[BeLo]

Have you seen the Phonak cap domes? Do you think they might work for this too as they look tiny?

Did the silicone adhere well to the dome?

[Markismus]

@BeLo

Did the silicone adhere well to the dome?

If you mess up, it quite a job to get the domes cleaned again. Silicone sticks to silicone quite well.

[Markismus]

@BeLo

Have you seen the Phonak cap domes?

They are indeed tiny! What is it? 3-4mm? You could even do without, I guess. But the silicone would stick to the cap, not the receiver.

[sterei]

That is amazing!
Thank you for your explanation!

Can you tell us what silicone product you use and where you bought it?
What were the main criteria for your choice?

I would then see what I could get in my country.

Silicone sticks to the receiver:
I would imagine it would be easier to pull it off the receiver if you first wrap the receiver with a tiny piece of PE plastic foil. The kind you use to store food in the refrigerator.
PE is almost impossible to glue

The foil can then be easily pulled off with tweezers.

[Markismus]

@sterei

Silicone sticks to the receiver:

Nope. It sticks to the silicone dome. Exactly, as if planned.

@sterei

Can you tell us what silicone product you use and where you bought it?

Look at art stores. It’s for making molds. It’s called poly-addition 2-component silicone paste. I bought mine here.
The reasoning was quite simple: I had to handle it with my hands and put it into my ears.
Normal silicone takes 24h to cure. And I really dislike silicone even when I have to use it in the bathroom or kitchen take make things watertight. I mixed some with cornstarch, but it still takes more than an hour to cure. This is extremely cheap, easy to get your hands on and clean. It cures in under 10 minutes. You’ve got about 2 minutes to work with it. It’s nice.

You could paint it with a finish if you want them to be a bit more durable or if you want it to be a bit thicker, so that it blocks the ear bit better. However, those are expensive.

[Markismus]

Today the Vented Domes 4.0 M arrived and I went ahead and put silicone paste around them. As the hardest part yesterday was removing the domes from the old receiver to the current receivers, I skipped this step and immediately used the current receivers.
I mixed 2x 0.50g and made a roll of about 1mm in diameter ( 9.5 + 2x1 is approx. 11.5.) That was too thin, as it broke to easily. Next time I’ll have to make the roll about 2mm thick.

I put them into my ear canals and let them harden. I twisted the plastic rods around the wire and put some cellophane tape on them to fix them to the casing. This way they didn’t slip out.

I cut the receivers free. You can see that there is a gab between the rim of the dome and the receiver at the back. In front both the vent and the receiver holes are kept free from paste. As expected the M domes are more bouncy than the S domes. Oddly enough, they result in ovals, with the smallest diameter 0.5 mm smaller than the M domes.

The result: The piano sounds like a baby grand!

[sterei]

@Markismus

Nope. It sticks to the silicone dome. Exactly, as if planned.

Ok and sorry, I got that wrong

@Markismus

Look at art stores.

Thanks, I’ve seen some there but was afraid it would be a mistake

[BeLo]

Have you ever had any problems with skin irritation and that silicone?

I found this stuff and I thought that I might give it a go:

https://www.amazon.co.uk/gp/aw/d/B00OBI0570/

[Markismus]

No skin irritation.

However, anything I put in my ears starts itching within days if I don’t clean them properly.
The HA wipes work. Isopropyl alcohol works. Peroxide works. Cleaning alcohol works. Basically everything that I tried when I ran out of the previous fluid works.
I use a cotton swab and clean both the ear canals and the silicone. 30-second-itch-solution.

[dankailo]

Take a very very small amount of your wife hand moisturizer to apply into the ear canal with the cotton bud after cleaning with alcohol (provide your ear is not oily type).This help in my ears canal irritation.

[sterei]

My first silicon DIY molds!

I have used power domes because I had some at hand.
After three days (still) no problems with itching.
Leakage from low frequencies is about identical.
But feedback limitations are noticeably reduced.
I will take further attempts with different ventings in the next few days.

[Markismus]

Nice! Didn’t know that there were brown domes. We only get greyish domes.
I found that the vented medium domes could rotate if you cut them back too far. Good to see that you cut them allmost at the end.

How is the sound block when you disable the mics? Also about the same as power domes?

How do you assess leakage? With an AudiogramDirect measurement?

[sterei]

They are the original Phonak domes. The picture is a little too brown in color.
I wanted to make the moulds as long as possible so that they should seal better. The downside will then be removing them from the receivers.
Leakage is about the same as with the domes.
Yes, I made a comparison with AudiogramDirect.

[Zebras]

@sterei

Leakage is about the same as with the domes.

Is there any point in having the DIY ear moulds then?

[sterei]

For me yes!

I am a DIY-er and I like to tweak.

And I did not expect miracles from the first attempt.

I suspect a few places where the leakage could be caused. I’ll try to be a little more careful there next time. (Spreading the silicone mass under the dome, giving a little more pressure after insertion into the ear, etc.).

Then I would also like to investigate the influence of different venting diameters. And find the one that works best for me.

In the end, it may just lead me to know exactly what I want. Perhaps I will then order a mold from the professionals according to my specifications.

[Markismus]

Comfort

If I want to reduce leakage a custom mold won’t help. I will have to wear one with a shield that covers the outer part of the inner ear shell (according to my audiologist). After I turn 50, I’ll consider it.

However, I can’t wear power domes, because they become painful after a few days. I can’t wear large vented domes for the same reason. Medium domes are not as good for leakage, but at least they are not painful.
So for me custom molds is exactly what it says: customized domes somewhere between medium and large.

Piano
There is interference between the amplified sound of the piano and the piano itself. It’s probability the same audiologically as that what causes feedback. However, instead of a whining sound you get a piano that sounds off key. (So contrary to normal feedback, even with lower amplifications, the volume of the acoustic piano interfers.)

For me this is the reason that I started tinkering with custom molds. And every time I get a new aid, I have to experiment to get it right.

Of course you could get custom molds made for you, too. However, after less than a year the hard ones get less comfortable for me. Soft custom molds weren’t available yet. The price in the Netherlands was 140€ for a new set.

Anyone knows what’s available in the Netherland, nowadays?

[emile.heilbron]

@Markismus

Anyone knows what’s available in the Netherland, nowadays?

I did not understood your question…What are you looking for? Soft molds?
Then is it not possible to have for instance the soft silicone Pluggerz and adapt them to the receiver you want to use if you take out the filter…

(Sorry I do not know how to insert a picture in my post)

[Zebras]

Click on this icon to add a picture.

[emile.heilbron]

Thank you Zebras!
To @Markismus

The upper ones are soft silicon PluggerZ custom made molds.
The gray ones are my Phonak M90 one time my set with normal receiver and one time with the hard Phonak custom mold.