Perhaps like one of these?:
http://otohearing.com/index.php/oto-products-2/custom-bte-earmolds
@Neville, thanks for graphs! Are they calculated for custom earmold with no venting? I’m a bit disappointed - I though that occluded fitting could provide full gain in the highest frequencies, particularly when I have the audibility 4K and 8K a bit better than 1k-2k range. But I’m thankful for your investigation 
@NateS, unfortunately, the link don’t work, maybe it’s accessible only for Americans. Maybe show the screen, please?
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Oh, they may. Ignore the predicted feedback curve. But the limit of that white area represents the limit of the receiver, so that’s what you are comparing. It doesn’t really matter in the mids where there is so much headroom anyway, but there’s a little bit of relevant difference at the high end.
@brec, thanks for the picture. @NateS, it is skeleton. mold (number # 2).
@Neville, I think, the ~10 dB more gain in P compared to M may be useful for me - apparently, when Phonak Target fitted my Marvel 90 with P rec. it remain a little room to make gain higher - only 3-4 steps in general fitting option.
Does occluded earmold can isolate you from environment so well so that you have worser audibility? I realised that Marvel 90 can muffle the sound, so yesterday I turned off Speech in Loud Noise in AutoSenseOS and make switching betwen automatic programme in maximum speed.
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Thanks very much, brec!
I have another question - does anyone have custom molds with no venting? If yes, what inconveniences you have with it? Does you have more benefits than loss?
For me:
- I don’t have any problem with my own voice (sic!)
- when streaming, street noise are greatly reduced, although due to my “heavy walking” the hitting the grounds of my foots during steps makes more impact to hearing
- hearing during eating may be a problem
- My Marvel greatly processing the no-streamed laptop sounds (e.g. YouTube videos etc.)
- Not sure if the feeling of somewhat dulled sounds in the bars/restaurants results from occluded mold or AutoSenseOS feature.
How would I know whether I have a vent in my Phonak Slimtips? If I had one, where would it be located? I see one possible little circle appearing alongside the opening for insertion of the tip of the receiver, but I’m not sure it’s a vent or just a circle.
My first set of molds from Costco came with no vents. I think my fitter checked them for fit in my ear but would not leave them in, while she ordered replacements.
No vents is a really last resort attempt. Because of the way vents work, I don’t think there is a significant difference between micro vents (1 mm) and no vents, other than the no vent version can cause pressure issues in your ear.
So after replacing them, your hearing have been improved? What earmold/venting you have now?
Probably yes, therefore now I wait for the same earmold with minimal vent (pressure vent) to make comparison. Currently with no vent I miss omnidirectional situational awareness and, what is worse, I can’t use the “Speech in 360 deg.” program because it’s binaural and I need CROS for it (which don’t exist for Marvels).
I’ll try to make a comparison “no vent vs. minimal/pressure vent earmold” and describe it in new thread.
I not mentioned, I have the impression that lower sound (also of speech) are quieter with no venting earmold. Earlier I though it can be adjusted by modification of amplification in fitting.
Thanks, @Sierra, very usable informations. So, the conclusion is:
- if you want maximum benefits from directionality/noise reduction you have to minimal or 1 mm vent
BUT
- if you have normal hearing at low frequencies, you have to have more diameter vent. I found this table:
Maybe I should have 3-4 mm diameter, but I really afraid of no benefits of directionality, noise reduction or from my Roger Select, which may be useless in that situation. Not to mention about possibility of insufficient gain in 1-4K before feedback.
When I got custom molds I believe they were 2.5 mm in my better right ear, and 1.3 in my poorer ear. I got essentially zero feedback with them. However, I could not stand them in my ear. Especially when I was eating they would move and make noise. After one more refit with an open mouth, they were no better, and while I lasted about 3 months I gave up on them. I went back to Rexton closed sleeves in both ears. They are rated at 1.6 mm equivalent vent size. However, the real venting is the sum of the intentional vent plus any leakage vent. The sleeves obviously leak, as they don’t give me the same feedback protection as the custom molds did.
The custom molds did give me better isolation from noise. When the hearing aid automatic noise reduction kicked in, things got really quiet. This would happen when on the highway with a very smooth road. Almost eerie quiet. If someone spoke in the car however, they would immediately pick it up.
I believe that chart is only considering the vent reduction you need to give the hearing aid power to boost low frequencies. The other totally independent requirement is to prevent feedback. That is determined mainly by the amplification you need in the 3 kHz region. If it is high, then you are likely to suffer feedback from sound leaking out the vent. So, yes you may get away with a large vent with minimal bass loss, but if you have 3 kHz loss you still need a small vent to prevent feedback. That link I gave you on earmold acoustics has a more detailed explanation of it all.
The chart is from somewhat old article:
The issue is that you can only use one vent size. If you have high frequency loss which is going to cause feedback, then that requirement overrides the low frequency gain issue.
Exactly. So I will try a mold with pressure vent and give an opinion. Maybe the HA will let me to set more gain in the low frequencies even with vent.
The biggest surprise was depite maximally efective directionality and noise reduction in occluded earmold my performance of speech hearing in gym or restaurants was noticeably poorer.
If you are using hearing aid software be aware that the gain curves you see are basically in the ear canal sound levels. You don’t know what the hearing aid gain is that is being used to achieve that sound level. The software behind the scenes is changing the gain to compensate for changes you make in the venting. The venting can help or hinder the actual gain. I wondered why one could change the venting drastically but it had essentially no impact on the in ear sound levels. The reason is that the target level does not change. The actual gain applied behind the scenes does to achieve the same sound level though.
I admit it is somewhat difficult to understand for me, but in other words you mean that software “think” that given gain with no venting is enough for particular situation, but in reality it is insufficient for me because e.g. my ear canal may be other than predicted in Phonak Target?
It may be true because I have no REM so far, I’ll have it when I decide to buy Audeo Marvel 90.