Custom Molds

Hearing Aids
#1

I recently purchased a pair of Resound Forza aids. The Audi did not mention custom molds being required but i noticed that if I plug my ears lightly with the aids in, the sound is definitely louder, more bass and maybe clearer. I have also noticed that when I wear my wireless headphones over the hearing aids, the sound is much better, in fact it sounds the best I have heard in ten years, almost natural (as I remember it).

My question for you experts is, looking at my audio-gram, should the Audi have suggested custom molds or is it possible we can eventually get the adjustments to the point I am satisfied without molds. I have had one adjustment to date and the sound is still not great. Thanks

#2

I am a fan of custom molds. I suspect that some audis start out new wearers with the other alternatives simply because of sticker shock. One less expense.

Congratulations to my grammy twin!! :wink:

#3

I too am a fan of custom molds. Talk to your audi and see what they say and what the price is. Costco charges $40 apiece for custom molds.

#4

You have a ski slope loss (which is normally for the domes) but its also quite flattish as its not a steap slope. I would of gone with customs molds and a vent.

#5

Thanks for the info. I will go back to Costco and order them. Do the molds with vents cause occlusion? I like the tulip things he used as there is no occlusion but I guess the idea is to hear better. If that requires molds, so be it.

#6

My question for you experts is, looking at my audio-gram, should the Audi have suggested custom molds or is it possible we can eventually get the adjustments to the point I am satisfied without molds. I have had one adjustment to date and the sound is still not great. Thanks

#7

Definitely on the RHS, optional on the left. Just a basic canal mould with a small vary-vent would make a huge difference.

The problem is the Resound receiver is shaped like a sugar cube: not brilliant in any way. I had a comparison in here recently with one of my customers who has a Mind 330 on a standard power dome (with a similar loss to the OP) and is getting along great, but the NHS gave him some free Resound RIC as a comparison. Basically they don’t have enough power either because the fitting algorithm isn’t punchy enough or the feedback manager walks all over the output. The Brick receiver struggles from square peg /round hole sydrome, even though the newer domes are better.

So: OP, you’ll do much better with a mould, as it will allow the aid to be more effective before the FBM starts clamping down on the signal; as long as there’s enough space to mount the receiver properly.

#8

custom molds will definitely improve your sound quality. you may get a little occlusion at the start, but i think you will find that the better hearing far outweighs that. if properly vented i think you will be just fine. i would recommend trying the molds.

#9

Could one of you more knowledgeable contributors explain the purpose and sizing considerations of vents in custom molds?

Thanks…

#10

Basically it’s a low pass filter, the larger the hole the more sound is let through, up to about 4-5mm when the ear becomes effectively ‘Open’. The length of the hole and taper cause particular resonances to occur, which are incorporated in the acoustic fitting of the aid. The greatest losses occur in the low frequencies, HF are better preserved.

Smallest venting at 0.5 mm in some CIC is really just to allow pressure fluctuations through rather than sound.

Your loss will infer a particular vent, but these are not hard and fast rules, as some people will prefer a more or less sealed fit depending on the degree of occlusion experienced. Ballpark figures: more than 60dB in low frequencies, the ear can be virtually sealed, 40-60 dB would be 1-2mm, 20-40 dB would be 2-4mm and 0-20 dB needs to be as open as possible - within the size constraints of the device.

Broadly speaking RIC should follow a similar pattern, but they don’t always as recent developments in feedback managers and component placement have allowed for potentially more ‘open’ fittings.

#11

Thanks.

That was very informative.

#12

Um bongo and dockristin,
Thanks for the input. I went back to the audi and he made a form for each ear to be used in making the mold. There are two different materials they use to make the molds. I think they were silicone and acrylic. He recommended silicone saying it would fit better.
He also said they should be replaced once a year. Is this true?

#13

Ive been told that silicone starts to strink after 6 months and you ears carry on growing all your life no matter what your age so yes roughly a year is right for getting them re done.

I will be having new impressions taken after having my silicone molds for only 7 months as they are causing feedback problems (that is normally the tell tail on when you have to get new ones done).

#14

Not so much the initial fit, but the amount they move ‘with’ your ear.

If it was me I’d ask for a ‘carved shell’ if possible, as they are far more comfortable.

#15

That sounds like an NHS response :wink: :smiley:

Some grades of silicone can shrink over time, but it’s variable and certainly not a reason to omit them from a selection. Wax also causes deterioration of some materials too.

Getting a new mould on annual review is certainly good hygiene, but really might not be necessary in terms of materials or fit. As ever ‘it depends’ on lots of things including your skin’s ability to be in contact with various materials. ‘Growth’ is a little misleading as the cause of poor seal, as most of the variation in your ear canal shape (and the subsequent slit venting) is caused by the dynamic movement of your jawbone (TMJ) pressing the cartilage against the mould and subsequently deforming itself.

#16

No NHS response as these ones are private. NHS won’t allow new molds for 2 years. Drives me mad as they only last about a year, give or take, depending on things.

The ones I have now are color and I haven’t had color for a long time, I’m wondering if the color stops them lasting that long.

#17

I have just been fitted with new silicone moulds (vented) to replace ones that I have been wearing for over 7 years (non-vented).

The difference between the old non-vented moulds and the new vented ones is quite remarkable. Every time I put in the hearing aids with the old moulds, they would squawk and squeal for a few seconds because of the poor fit (shrinkage). But if I shoved them in so as to provide a proper seal, the occlusion effect made them intolerable for use in normal conversation.

The new ones fit tightly enough so there is no squeal when I insert them and turn the aids on. And the addition of the vents reduce the occlusion effect to the point where I can carry out a normal conversation with relative ease. Apparently there is a mathematical table to work out the proper length and width of the vent so as to reduce certain frequencies (in my case lower vocal range). My audiologist did a great job with this.

Another benefit is that since my Ambra SL aids don’t need to adjust to feedback squeal, they do not need to cut off any of the higher frequencies at start up. So I am now for the first time able to benefit from the full spectrum of sound that the aids provide.

As for replacing them annually, I hope not. They are very expensive to make. As long as they are cleaned daily (I use antiseptic moist wipes) and the ears are kept clean and healthy, there should be no problem. All that needs to be replaced are those darn tubes that harden up and turn brittle every 6 months (because the medication I have to take reacts with the vinyl of the tubing).

#18

Gramps,
Whether your on medication or not you would still have to replace the tubing at least 2 if not 3 times a year. Mine turn hard or stiff and need to be replaced about 3 times a year; if your outside a lot, the UV from sunlight will stiffen the tubing up pretty fast. I used to have the audi change my tubes but after watching them do it and then having to replace the ear hook because it would break a few days later because they wouldn’t make a cut in the tube were it meets the hook to release it and they would just yank on it to get it off, I started doing it myself and have had no problems since. I’m not sure how long the silicone molds are suposed to last but the hard acrylic ones will last for years as long as you don’t gain or lose a lot of weight and take care of them.

#19

Ear gene ear lotion are good for that matter. But i would suggest you should go for a check-up before applying a therapy.

micromold

#20

Silicone molds start to shrunk after 6 months so yea they will have to be replaced more regualrly then the hard molds. Fact life, I am afraid.