Why does a low frequency loss require a custom fit mould?

I’m going to my NHS appointment next Monday and would appreciate some advice so that I can talk with some degree of confidence to the audiologist.

I have a low frequency loss of around 45/50 db at its worst and sloping back up in the high frequencies. I have been fitted with 2 Siemens Chroma S and custom ear mould(with a small air vent) with open fit tubing. I absolutley hate the moulds and feel blocked up and even at times dizzy. It has not helped my hearing in the classroom situation at all (I’m a teacher) so have stpped wearing them as I cannot do my job properly with them.

I would prefer a more open fit but the audiologist insists this is what I need and would even use the same mould for RIC aids which they hope to get soon. This was not what I was led to believe when I saw a few private audiologists a few months ago.

Could someone in the business please explain to me why the custom mould is necessary? Could I manage a more open fit style especially with RIC aids?

In other words how do I explain to the audiologist that what I have been given is not working for me?

Will I have a better chance with private aids or will I just be offered the same?

I’d suggest checking with www.americahears.com, faxing or emailing your audiogram, then calling them for their opinion of whether a mold is necessary. I found the audiologist who answered their phone when I called to be very knowledgable and helpful.

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For What Its Worth…
(I am not an Audiologist just another Low Freq Loss HA user. My scores, posted below my signature, seem close to what you have described)

I saw 4 different AuDs and they all said I would probably need to use custom molds. However, every HA that did trials on was fit with open or most often tulip domes (often called plus domes).

The process of getting comfortable and effective custom molds is difficult but for a low frequency loss, often needed. RIC or BTE, with either one you may have better effect with the more closed effect of the custom molds.

Your AuD can try to adjust the vent size to give you a more open feeling and that may help.

The reason for the closed mold, as it was expained to me has to do with containing the low frequency sounds without having to go to a more powerful HA. Some mold companies even recommend special tube/vent configurations for Lo Freq loss (horn or reverse horn not sure which).

Getting the programming just right is a challenge also. Too much mid & high or noise reduction & the lows get lost or overwhelmed.

Ask your AuD if you could try the domes, (He/She will have to adjust your programming for it) Personally, I found domes to be too open, and while I could hear women & children fine, I could not hear men or get good speech discrimination with TV.

Takes alot of patience on both your part & the part of the AuD to get an effective HA/Dome-Mold fit for low frequency loss as most of the instruments & programs are designed for the more common high frequency losses.

Good Luck.

Post back with how it goes.

I think Squeezer explained it pretty well. I also have low frequency loss (50-60 db at 500-2k). When I consulted with America Hears, the person I spoke with said that I really wasn’t a good candidate for open fit. However, because I have difficulty being properly fitted with molds, the dispenser there thought maybe I should give open fit a try anyway and see how it would work for me. I wore AH LOF aids for about 30 days, and I concluded that they really weren’t helping me as much as I needed them to, particularly with men’s voices. So, I traded them for traditional BTEs with custom earmold. As Squeezer said, the open fitting vents out the low gain - you really have to capture it with a mold. There are, however, many different types of molds. If you hate the mold you have, you might need to try something different. You might be more comfortable with a traditional BTE with an earmold. Your audiologist should be able to work with you on finding something you find more comfortable than what you are currently wearing.

I feel the programming isn’t just right. With my aids and a quiet classroom (apart from the background noises of a school) I was not able to hear the children any better than without the aids. The only time I noticed a difference was when the children were standing right next to me. Then I noticed they were louder - but then I never had any problem at that distance anyway.

Ask your AuD if you could try the domes, (He/She will have to adjust your programming for it) Personally, I found domes to be too open, and while I could hear women & children fine, I could not hear men or get good speech discrimination with TV.

I think I will do this and see how I get on with them assuming I will be allowed to do so. I just feel that the custom mould is blocking out all my good high frequency sounds which as far as I’m aware provide the clarity in speech. It seems daft to do this.

Someone suggested letting my custom mould sit loosely in the ear to give an open fit effect just to see how it would work. I found this far more comfortable and the aid seemed to provide more volume which is what I want. Although I have to say I tried this at home and not on the challenging classroom situation.

Takes alot of patience on both your part & the part of the AuD to get an effective HA/Dome-Mold fit for low frequency loss as most of the instruments & programs are designed for the more common high frequency losses.

I’m beginning to realise this. My loss does not seem to be very common.

Post back with how it goes.

Will do.

Thanks for your post - it has been very helpful.

It’s not so much the feeling of the actual mould (although it does give me a sweaty ear), it’s the pressure within the ears that the moulds give that are the problem. It’s like I am constantly on a plane which is coming into land. Even hours after removing the aids I still have this pressurised feeling.

You might be more comfortable with a traditional BTE with an earmold.

This is what I have at the moment. It’s the narrower open fit tubing but leading into a smaller custom mould. I did have the full mould and that was just the same but far more noticeable.

I also have a similar hearing loss, so more low frequency loss and less high frequency loss. I have used open fit aids quite a lot, although my current best fitting is microSavia 100 dSZ with micromolds and small vents. I also use Savia 211 dSZ with open domes. Here are my numbers:

Freq/Left-Right
125 / 55 - 65
250 / 55 - 70
500 / 55 - 60
1000/ 55 - 65
2000/ 50 - 60
3000/ 35 - 45
4000/ 25 - 35
8000/ 25 - 35

I got microSavias a couple of years ago privately, I got them for a trial with open domes, and they helped me immediately a lot. So I think Jem16 that even almost any open dome fitting would be better than what you have now! However, your aids may be set especially soft to get you accustomed using them, so they can probably give you more. But when I got microSavias I felt that I was not ready to block my ears with close fit aids. I could not hear the softest speech voices with them set open, but when I tried closed fittings I found them confusing, distracting, lacking clarity and ergonomically uncomfortable. There’s been no big changes to my hearing since then, but what has changed is that I’ve got the programmings a lot better and I’ve got a lot more used to hearing aids.

One possibility is to get some hearing aids which you like and use them first open fit. You may not hear very soft speech voices that way, but you can get used to them. Later there may become a day when you want to close them. They may also be closed with “power domes” or “tulip domes”, where power dome is about the same than a micromold with a small vent, but I personally prefer micromolds though. If it’s difficult for you to get accustomed using hearing aids you might also benefit of a remote control and multiple programs. Then you could use “mute” if you are tired and listen through the open domes as if you had no hearing aids, and try with different programs which sounds the best for you.

You wrote that you have a meeting with your audiologist on Monday, and it’s now Monday, but maybe what I write might help for the future adjustments. If you continue with close fit aids the next thing you need is a lot more soft voice gain. If you can hear so poorly with close fit aids as you described, then the programming is either not good or those hearing aids are not ideal for you. Raising soft voices doesn’t necessarily need to mean raising loud voices too, so you could also ask for only soft voices set more hearable. If you have hearing aids with enough channels (maybe at least eight) they can be set differently for different frequencies. What I find the most important frequencies for soft speech are 500 Hz - 3000 Hz, and with close fit aids one also needs to pay attention to the voices above 3000 Hz. What comes to voices somewhere below 400 Hz, I can’t find them adding anything to speech clarity, but there’s background noise there, so I don’t need much of those at least for a noise program. Amplifying loud voices still louder doesn’t help me, so I tend to have my mpo (maximum power output) not very loud. That has made close fit aids more intelligible and less distracting for me. In fact, they are now so good that I tend to forget that I have them. :slight_smile: But it was much easier to start with open fit aids and I also found other molds than open domes ergonomically very uncomfortable at first, but I have got used to having something in my ears little by little and now I don’t feel micromolds much.

If you decide to look for good open fit aids, pay special attention how loud you can get soft voices around 500-3000 Hz. In order to hear soft speech voices well I need 40 decibel voices to become somewhere around 80 dB voices around this region. Still you need to try the hearing aids because the curves on the fitting software screens are approximations. My micromold fitting with microSavias looks quite similar to my open dome fitting with Savia 211, yet I can hear a bit more with the microSavia micromold fitting. But both of these hearing aids are helping me enormously, so if your aids are not helping you then you can get something a lot better, whether open or close fit. Using hearing aids open fit when you have low frequency hearing loss may mean compromising the softest speech voices, but you can change them close fit aids later so you would not be losing anything. Note that you need adjustments to the aids when you change between open and close fit because the ear canal has different effect on the voice.

Kind regards,

Leia

Leia,

Thanks for your post. I read it after I had seen my audiologist but it was still very helpful.

We had a good long chat and he understood where I was coming from. He brought lots of different vents to try with my mould to get things sounding better. In the end we went for a completely open vent and he only had to reduce the gain slightly to avoid feedback. He explained that with my loss I needed this gain in the low frequencies and the more open fit domes would not work with the aids that he has available at the moment. This is with the NHS in the UK and the aids are supplied and fitted free of charge. All batteries and repairs are also free.

He has told me that the NHS now have a contract as from November to supply RIC aids and they are waiting for supply of these. I have now been told that I am a prime candidate for these and will be the first to get them as soon as they are available. This will allow him to try the more open domes to make my ears more comfortable. He has described them as completely open (propellor shape), partly open (fin shaped) and closed (dome). He hopes to use at least the middle option with me. Unfortunately he does not know when exactly they will become available but expects them within months rather than years.

I can go privately and get these now but they would cost at least £2000, possibly more £3000 and only include a 2 year guarantee with no batteries. It therefore seems sensible to wait a few months and see how I get on with the changes he has made.

My left ear feels quite comfortable now. My right ear still feels as if something is there in the ear ( obviously there is). I don’t get the occluded feeling though anywhere near as much. I feel it a bit, more so in the right ear. Why this ear is different I do not know as it’s my left ear that is slightly worse - perhaps of course that is why I notice it more.

Meanwhile I have been given an extra programme for my classroom situation. This cuts off the 360 degree microphones and gives me a focused microphone which only hears what is in front of me. I won’t be back at work until the 5th January to try this out though. I can use the button on the aids or use the remote that I have been given.

I asked him for a copy of my audiogram. What I do remember is that his audiogram made my ears a little worse than what I tested with the private audiologists. The NHS test was done in an open room, albeit soundproofed, whereas the private test was done in a soundproofed booth.

Both ears are virtually identical with a slight improvement in my right ear. However he only gave me one set of figures.

250 - 30
500 - 60
1000 - 60
2000 - 30
3000 - 25
4000 - 10
6000 - 5
8000 - 20

Is it possible to use open domes with low frequency hearing loss and increase the amplification on the lower frequencies to make up for the difference?

From what I have learned it is not possible as more gain in the lower frequencies will create more feedback, thus giving you a squealing aid. I do notice this squeal when I cup my hand over my ear. This was not there when the vent was more closed. However fortunately in normal wear I do not go around with my hand over my ears!

The RIC aids will allow more gain as the receiver is further away from the microphone.

I have tested with the frequency analyzer software Spectrogram 16 that my feedback with Savia 211 and open domes which comes when hands are close to the aids is around 2000-3000 Hz (Spectrogram is free to download, http://www.visualizationsoftware.com/gram.html ). When I have the soft voice gain of low frequencies at its maximum with these aids I’m not yet close to getting any significant feedback with low frequencies.

Kind regards,

Leia

It is a delicate balance between increasing the low frequency and noise reduction. Too much noise reduction and you lose the low tones. Too much low frequency boost and noise becomes a bigger problem. In addition, too much low boost and you can end up masking the mids & highs (which would probably make it even harder to hear the children since that’s where speech mostly is). Too much amplification with an open fit & you will trigger feedback.

IMHO, RIC Aids (aka RITE) are to some extent, just the latest fad in HAs along with bluetooth) and just because it is the newest thing on the block, does not make it the best for all losses. I have a low freq loss as I said, similar to yours and I do have RITE Aids (EpoqXWs) but I was really on the fence about keeping them and am still considering asking the AUD to swap them for standard BTEs in order to simplify getting a good custom mold fit.
(When I spoke to someone 2 years ago (when RITEs were not as heavily marketed), they did not recommend them for low frequency losses)

The original theory with RIC(aka RITE) aids, was that placing the speaker in the ear would reduce the high frequency resonance that can develop in the thin tubes & provide a smoother frequency response. Also, it was thought that moving the speaker farther away from the mics would allow more amplification (gain) without producing feedback. However when coupled with an open fit dome, the path for sound to “leak” from your ears back to the mics and cause feedback is still there…
Here is a link to article on benefits of RICs & feedback…
http://www.audiologyonline.com/theHearingJournal/pdfs/hj2008_01_p28-34.pdf

Standard BTEs with a tube (non-rite), might give you a longer, larger space for the Low frequency sounds to develop. With a speaker in ear, the space left for the sound to travel is smaller.

From a logic standpoint, (and I may be way off base here so AuDs correct me please) I compare the acoustics of my HAs, Ears & molds to musical instruments and audio equipment. It may not be a true comparison, but from logic standpoint it makes some sense to me. A tuba has a longer more voluminous path than a trumpet. The base string on a guitar is thicker & has to move slower & farther to create an audible low tone. Cellos are bigger than violins for a reason. The bass speaker on my surround sound is the largest component in the system. Bose markets it’s improved accoustics on the basis of a serpentine sound pipe that allows creates a “concert space” tfor he music to resonate and grow in.

From that standpoint, it makes some sense to me that amplification of bass tones will be more dependent on the volumetric & accoustic characteristics of the listening space, rather than just the amplification & speaker location…

When you are talking HAs & Ears & Molds, the volumetrics are are much smaller but theory should remain the same. Keeping the correct balance in amplification, retaining low sounds, and giving it room (volume) to develop the low frequency resonance rather than be damped, will for the most part be a function of the tubes, molds & your ear’s inner archictecture. (HAs are designed & tested against a 2cc volume as a standard, your ears may be more or less than 2cc.)

Another down side to RIC Aids is getting a good fit with custom molds if your canals are narrow & not straight enough. The Speaker is rigid & straight and need a stright path to seat nicely in a mold.

The AuD has set you up with a manual select directional program. (I use one when in the car for the radio and at home for tv or when I am in a restaurant to hear my companion better) In a classroom, this should help with noise reflecting off the surrounding surfaces.

The AuD could also adjust your program to make the amplification more linear across the frequencies. (I hated this setting, but you might like it) If you are in a “closed mold” the AuD can program the Aids to amplify the mids & highs little bit more to allow the HAs to provide the sounds that are being blocked by your closed molds.

I did not notice if you said the molds were hard of soft. Hard molds that are a hollow shell style will have a tiny vent. (Which can be widened for a more open feel) But solid body molds soft or hard, will have a much larger vent because the vent has a longer length to travel. Vent size & resulting feeling of occusion is, in part, determined by the length the vent has to be, and vent shape & length will also have a big effect on the sound you hear from what the Aids put out. Real Ear measurement (aka REM) can be of help too.

While my AuD & I search for the right molds for me, she has also provided me with some select-a-vents. These are small tubular inserts of different inside diameters that I place in the molds exsiting mold vents to make them smaller. So I can “play” with the vent size & determine the right balance of occulsion v. “open-ness” that I am comfortable with.

You may also want to check with the AuD to see if the aids are set up in acceptance mode. That is an automatic program that starts the user with less than optimum gain to start and gradually increases gain over a few weeks to allow the wearer to get used to amplified hearing without getting overwhelmed by it.

Don’t give up! If anyone said it would be easy, they did not have a low freq loss. When it is finally the right combo of Aids, program, tube/speaker & mold/dome, it will be worth the effort.

Not sure I understand what you mean by more linear?

I did not notice if you said the molds were hard of soft. Hard molds that are a hollow shell style will have a tiny vent. (Which can be widened for a more open feel)

It is a hard mould with a vent. The vent has now been left fully open - i.e. no “stopper” in it to close the vent in any way. The audiologist tried a few different ones from almost completely closed to partly open to fully open. We plumped for the fully open vent which has helped the occluded effect and did not lose much gain.

You may also want to check with the AuD to see if the aids are set up in acceptance mode. That is an automatic program that starts the user with less than optimum gain to start and gradually increases gain over a few weeks to allow the wearer to get used to amplified hearing without getting overwhelmed by it.

That I don’t know.

Don’t give up! If anyone said it would be easy, they did not have a low freq loss. When it is finally the right combo of Aids, program, tube/speaker & mold/dome, it will be worth the effort.

I shall try not to give up. The right ear is the one giving me most grief at the moment.

I have been experimenting with closed domes that I am venting myself. I have had some satisfaction with this. The primary advantage is the domes are cheap, so you can experiment a lot and “tune” it yourself.

It was described to me this way…
Visualize your audiogram, it looks like a ski slope with the bottom of the hill on the low freq end and the top on the high freq (reverse of what most folks have)…
The graph of the program settings could look, in shape, like the mirror image of your audiogram. ie. most gain where your loss is, little to no gain where you hear well. The way more linear was described, the program graph was a straighter line than the audiogram graph which gave added amplification for my mids & highs and would smooth out the overall sound delivered to me. The goal was also to boost some of the sounds which were blocked by my molds.

I have not ever been asked to use completely occluded molds, I don’t think I would like it much. So far, the challenge is finding just the “right” amount of openess to suit what & how I like to hear.

That is my next step also. I am waiting for the AuD to send me some of the new power domes from Oticon so I can try out other “outside the box” ideas.

Thanks for the description of linear - I get the general idea.

I am trying to persevere with the aids and have worn them for the majority of the last three days. I still find the moulds uncomfortable, especially the right one, although I don’t feel quite as blocked up as before.

I feel there is still room for improvement both in sound quality and comfort. Sound still sounds a bit like an echo and a bit tinny.

Apparently for those of us with reverse slope hearing loss who also have the weird super dog-hearing in the high frequencies, open fit hearing aids might be better because they let in the high frequencies that our adapted brains need to still hear to understand speech.

I am not sure that lower frequencies need to go through a short tube from a BTE hearing aid to be heard well. People generally hear low frequencies fine with headphones when listening to music.

Did you read this article? I found it fascinating although I’m not sure my high frequencies are that good.

http://www.hearinglosshelp.com/articles/reverseslopelong.htm

What does your audigram show?

I am not sure that lower frequencies need to go through a short tube from a BTE hearing aid to be heard well. People generally hear low frequencies fine with headphones when listening to music.

Not overly convinced on that one either.

The voice including low frequencies needs to be taken close to the eardrum with open fit aids for at least two reasons. One is that otherwise it’s too close to the microphones and that would cause feedback. The other is that otherwise it would be hearable to other people close by, and at least personally I would not be ready for that. But currently I don’t have trouble with these things, so I believe the low frequency voices could be taken louder than what I get with Savia 211 open fit. Also, I can’t get the low frequency voices of these aids endlessly nonlinear, in this case meaning that I can’t raise 40 dB voice as loud as the loudest low frequency voice which these could produce. So I believe the tube limitation isn’t the reason why I can’t hear perfectly with these. However, I’m not even sure if the reason that I can’t always hear all speech with these is because of the low frequences. It may be, but it may also be that I can’t get soft voices around 2000-3000 Hz loud enough because of the feedback limits there. When I use a micromold fitting the soft voices of 20-40 dB around there are amplified more than with open domes and the feedback phase inverter. The feedback limits come faster with high frequency voices than low frequency voices, but why I believe it’s not a problem for those who have only high frequency loss is that they can hear soft speech because of their good low frequency hearing. The problems with low frequency and high frequency hearing loss are different: to simplify some, low/middle frequency hearing loss makes it difficult to hear soft speech, high frequency hearing loss makes it difficult to hear in noise. But when I look at your good hearing around 2000-8000 Hz, Jem16, you would probably do better than I with open fit aids. And my problems with the open dome fitting are relatively small, and my hearing with them can’t be even compared to how I hear without aids because the difference is as night and day.

Squeezer53, I’m sorry but I did not understand your explanation about linear. How I have learned this term is used with hearing aids, it means that the input/output graph is a straight line of 45 degrees. This means that every voice of that frequency gets the same gain, so if 30 dB voice became 50 dB voice, then 40 dB voice would become 60 dB voice (20 dB gain for both). Because the input/output graph is taken differently for different frequencies, the nonlinearity can also be different for different frequencies. If there’s some mistake in my explanation I would be happy to find out about it. :slight_smile:

Kind regards,

Leia

I think I agree here. My hearing is good in the area that gives speech clarity. I just need a little more volume at times. However blocking out my good hearing seems way out of line.

I think I still have a long way to go to get this right. At the moment there is not a lot of difference between hearing with and without aids. Yes the volume is louder but it drowns out the speech I want to hear.