Noise reduction and open fit


I read a lot of posts that concern noise reduction, or speech in noisy environments. It has occurred to me that if one has an open fit, noise reduction, or speech in noise will not be very effective because of sound leaking through the dome vents. Also, directional settings probably wouldn’t be as effective for the same reason. I set my aids to the most directional setting, stood in front of the TV, and slowly rotated my body. I couldn’t detect any difference in sound regardless of direction. Do those with a long experience wearing aids with open fit find this to be true?



I definitely notice it (or not notice it?) in terms of noise reduction, but I still find the directional effect to be quite noticeable.



That TV test may not be a great one. What I expect you would notice with the directional settings in an open fit would not be a reduction of noise in back, but a slight increase in clarity of the person speaking in front of you in a noisy environment.

If you are in an open fit now, with your hearing loss you may well be able to manage a more closed fit. The trick will be to balance a potentially negative experience of your own voice relative to any improvements that a closed fit will give. Depending on the shape of the ear canal, in many cases a closed dome will still not provide a truly closed fit, so chances are high that you could use closed domes to reduce the venting without significant own voice issues.



Here is a link to an article on the subject. It is rather dated (2006), and it may only be applicable to the Oticon HA’s used in the test. However the conclusion of the test was that if properly set up directionality is not compromised with open fittings.

Maintaining the Directional Advantage in Open Fittings



That may not be apple’s to apple’s. I don’t think the directional beamforming of today existed in 2004.



See the 2016 review article posted by MDB in 2017. Also towards the end of that thread, I reference a 2006 Widex technical paper cited in the review on open vs. closed fit. Both articles say that you don’t get maximum benefit out of noise reduction and directionality with an open fit. And also imply that you may get better speech recognition with a more closed fit because of potential cancelling interference between sound from your HA’s and possible out-of-phase sound by passing your domes, depending on the acoustics of your ear canal. I like a more closed fit as I perceive the above to hold for me but maybe part of its just the placebo effect! (for me).

P.S. Just checked. The direct link to the Widex Pro site for their 2006 technical paper is back to working.



Neville, I was basing my statement solely on perceived volume, not noise reduction. Given that our ears respond in a logarithmic fashion, if the change was slight, I might not have noticed it. I will have to try it again with a continuous tone source. I can’t use a closed fit. The sound of my own voice is just too much. It is like I have my fingers in my ears continuously.



Curious if there is an operational definition of a closed fit. It’s pretty clear a perfect seal is impossible, so how much of a leak is still permissible to be called a closed fit? Seems like this really isn’t a binary choice but one with shades of grey.

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It’s like putting your wallet in a different back pocket. You habituate to it after awhile and it becomes the new normal. Probably depends on one’s perceived benefit, too. Since I think speech is noticeably clearer for me with a more closed fit, it motivates me to adjust to any “voice too loud, fingers-in-the-ears” sensation.

I agree. That’s why I like using the feedback test for deciding how far I am into the shades of grey. It’s prett y hard to decide subjectively, for me at least, when you’re hearing sound from both ears in your brain, the feedback test, which is ear-specific helps me decide whether the fit in a particular ear is as closed as I want it to be.



There are several articles about using REM to verify an open fit. Several ways to look at it. To me “purest” way to look at it would be the fit interferes with the ear’s natural resonance that it’s a closed fit and hence, not open.



Would be great to post a link to one or more such articles - maybe there’s a good review article just as for the 2016 review that you posted and I reference a couple of posts above.



I usually post links when I think I’ve found something exceptional. Google: “verifying open fit hearing aids” and several articles (including audology online ones) pop up.



Plus, much of volume is carried in the low frequencies. Your hearing aids are amplifying your highs, so you could try again with a focus on voice clarity changes?

Fair enough. With loss similar to yours, it depends on the person.



Certainly, it’s a continuum of venting. With an open fit, you lose power to provide low frequency amplification. As you close down the fit you get more of those lows back. Sometimes a closed dome will essentially be an open fit if it is not a great geometrical match for an ear canal (e.g. ear canal is quite oval). Sometimes you can hack something that is slightly more closed than an open dome but not as bothersomely occluding as John finds closed domes to be with a pair of little scissors, and get around the occlusion problem while still giving a bit more amplification at 1 kHz, which is important for speech.

Maybe check this out.



The link Neville cites is the 2006 Widex technical paper on venting by Kuk and Keenan. It’s a very interesting read along with the 2016 review article mentioned by MDB in a thread on “Open vs. Closed Fit Article” - a review that also references the Kuk and Keenan paper as a seminal work.



That fingers in your ears thing is enough to make me just get by with no aids at all. I have yet to find a setting that gives me much improvement in recognizing speech properly, so the trade off between very uncomfortable hearing aids and comfortable deafness isn’t all that great.



With open vented domes I have no sensation of anything in my ear. Maybe you need to try a smaller open dome? A dome that is too big can fold over and occlude upon insertion.



Oh, I’m not saying that you should try to push through. Hearing aids need to be comfortable to be in your ears all day. If your hearing declines further in the future, that fingers in your ears feeling may fade.



There are choices for venting between completely closed and completely open. I have custom molds, which are about the size of dones but made specifically for your ear canals. Mine have select-a-vent which is a big hole with a set of vent inserts of different caliber. I go with the smallest vent that doesn’t occlude and I get great results hearing in noise, and no feedback.

With your hearing loss you should get good results.