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Things to consider before getting your custom IEM impressions done. The perfect fit. - Page 2

post #16 of 60
Thread Starter 
Quote:
Originally Posted by Mython View Post

Yeah, the hollow UV acrylic in the silicone mould is particularly cool - I'd often wondered how they went about doing this (I was previously wondering if it was done with a 3-D centrifuge, as is the case with certain types of hot plastic moulding), but no... time-controlled UV exposure; what a great idea.

 

The main question I have after watching those vids is why UE sometimes use laser scanning and sometimes use the hotwax-dipping method. Why the disparity? Obviously, they'll use the computer method if an audiologist sends them a 3-D laser-scan file digitally, via e-mail, instead of shipping a silicone impression, but that can't be the only circumstance under which UE are using that laser set-up because they have a scanner right there, in-house. Presumably, 3D printing of the laser scan is a more expensive process than the conventional, manual, wax-dipped silicone impression method, but still, that's no conclusive answer.

 

I'm also curious how they phase-align the various BA drivers in the shell - do they simply place the BA drivers in the shell the best way they'll fit, and then attempt to phase-align them electronically? I'm not sure that's possible, and yet there seems to be a wide disparity in BA driver placement, if one looks at photographs of various makes and models of custom IEMs.

 

Questions, questions! confused_face_2.gif rolleyes.gif


 

Those are really good questions! Now i'm wondering too.

post #17 of 60

@OP: thank you for your efforts!

post #18 of 60

Great thread.  I have lots of experience making my own impressions and the results are generally perfect fits.  I use a 1" bite block unless the manufacturer says differently such as for a silicone shell.

 

As you have said, all jaws and ears are different and a closed mouth could be better for fit, but for the first time it is hard to know.  Here is a link I found with great information:

http://www.hearingreview.com/issues/articles/2006-05_10.asp

 

post #19 of 60
Thread Starter 
Quote:
Originally Posted by average_joe View Post

Great thread.  I have lots of experience making my own impressions and the results are generally perfect fits.  I use a 1" bite block unless the manufacturer says differently such as for a silicone shell.

 

As you have said, all jaws and ears are different and a closed mouth could be better for fit, but for the first time it is hard to know.  Here is a link I found with great information:

http://www.hearingreview.com/issues/articles/2006-05_10.asp

 



That's a great article. Thanks for sharing this. I hadn't seen it before. Lots of insight there.

 

An important excerpt from it: "Let the material cure in the ear undisturbed. Do not touch it or press it into the ear. Kieper3 found that making a “tighter” impression by pressing the material further into the ear creates a worse—not better—seal for the resulting earmold."


Edited by Sproketz - 11/6/11 at 7:52am
post #20 of 60
Quote:
Originally Posted by Sproketz View Post





That's a great article. Thanks for sharing this. I hadn't seen it before. Lots of insight there.

 

An important excerpt from it: "Let the material cure in the ear undisturbed. Do not touch it or press it into the ear. Kieper3 found that making a “tighter” impression by pressing the material further into the ear creates a worse—not better—seal for the resulting earmold."



Interesting, but just to clarify - my remarks about pressing the silicone into the ear were specifically regarding the external ear - absolutely not pressing the silicone any further into the inner ear / canal.

 

My experience is from the standpoint that, as I originally remarked, my impressions were lacking in certain areas of the external ear, such as part of the anti-tragus.

 

In theory, it should be possible for a skilled audiologist to apply the silicone in such a way that all areas of the ear are contacted evenly, directly from the syringe, without needing any manual intervention, but the complex structure of the ear makes this a tricky task. Provided any manual intervention is done immediately (and without excessive pressure to distort the ear), before the silicone has begun to cure, I can foresee no reason why the resulting impression would be rendered inaccurate.

 

Well, each to their own. I know that next time, I'll trust my own experience and definitely request (moderate) manual pressing of the silicone into the folds of the external ear.

 

 

Now, back to my other questions - anyone know why UE only sometimes use the laser scan method, and how phase coherence is achieved in multi-armature IEMs?popcorn.gif

 

post #21 of 60
Thread Starter 

That makes total sense Mython. It's a good distinction to make.

post #22 of 60

my audiologist told me to make a calm chewing movement for like 3 or 5 sec, no biteblocks were used.

 

what do i have to expect from the fit ?

 

 


Edited by Samehada - 11/6/11 at 8:57am
post #23 of 60

It's interesting, reading that very detailed article, posted by average_joe (thanks, Joe!). The remark by 'Kieper3' is not discussed, just cursorily mentioned. Therefore, I'm trying to figure out whether it relates to pressing the silicone into the inner ear or the external ear. Since the remark relates to the 'seal', I'm surmising that it relates to pressing of the material into the inner ear, a practice which I would have thought would be frowned upon anyway, since it may present risk of injury to the ear canal or to rupturing of the cotton/sponge dam (thus, potentially, permitting silicone to come into contact with the eardrum).

 

A Google for 'Kieper3' is sadly unrevealing..

post #24 of 60

Ah, I just realised that 'Kieper3' is a typo in that article - the 3 should be a subscript reference number, as in:

 

3) Kieper R, Berger E, Lindgren F. An objective assessment of the effect of ear impression technique on real-ear attenuation of earmolds. Indianapolis: Cabot Safety Corp; 1991.

 

and also found it listed in a bibliography, elsewhere online:

 

 

Kieper, R. W., Berger, E. H., and Lindgren, F. (1991).  "An Objective Assessment of the Effect of Ear Impression Techniques on the RealEar Attenuation of Earmolds," Spectrum Suppl. 1, 8, p. 24. /796/

 

 

I'm digging into this for a few minutes. If I find anything, I'll repost.


Edited by Mython - 11/6/11 at 8:52am
post #25 of 60

 

 

Since the study by Kieper is probably a professional academic journal article (which generally are not freely available to laymen, instead requiring subscription to a particular professional journal database), I've been unable to locate Kieper's study on the internet.

 

However, during my Googling, I did find an interesting abstract about the laser-scanning method of ear impression moulding, in so much that it concludes that 'open-mouth' impressions are preferable:

 

https://www.thieme-connect.com/ejournals/abstract/sih/doi/10.1055/s-2004-815550


 


 

post #26 of 60

I have had great success with using a bite block except with one silicon shelled custom, the SE 5-way.  I think I accidentally did an open mouth impression for that and have some discomfort after about an hour of use.

 

Another thing to consider is how the actual custom IEM company makes the impression.  From what I know, shells from negative impressions (example is 1964 ears) are not the same as those that are made from scans (example is ACS hearing protection), but I don't have the data to really know so if the manufacturer says closed mouth, that is the best, and if they say bite block, use one.  If they don't say, then I would recommend using a bite block, especially for acrylic and consider a relaxed mouth for silicone shells.

post #27 of 60

Great info :)

post #28 of 60

Great article. Wish i had read this before taking my impressions. Would probably have skipped the whole refit process...

 

Took my impressions facing down with 2 fingers, the resulting customs would break seal whenever i looked up. Thus, had to get another set of impressions done, this time facing up.

post #29 of 60

Very informative. Will definitely take this into consideration when doing customs in the future ;) 

post #30 of 60

I appreciate I'm resurrecting a dormant thread, here, but I consider this thread to be permanently relevant (at least until such time as the Lantos 3D digital ear scanner, or variations thereof, become widespread, but it will take quite some time for such devices to achieve widespread market penetration).

 

Therefore, I'm just adding a few thoughts...

 

 

 

 

 

 

Generally-speaking, the rule of thumb is that if you're ordering silicone CIEMs (like Kozee, Spiral Ear etc.) then those manufacturers generally ask that you have impressions done with NO bite block.

 

On the other hand, most makers of acrylic  CIEMs ask customers to have impressions done WITH a bite block.

 

A big piece of advice to get a good fit is absolutely 100% do *NOT* speak while your impressions are curing in your ears - don't even smile, or even tense your facial muscles. I'm serious, this makes a big difference. Sit there with your facial muscles as relaxed as you can manage (even with a bite block, it is actually possible to relax the facial muscles - I highly recommend that you practice this before you go for your appointment). I recommend that you deliberately 'zone-out' while your impressions are curing in your ears - if you turn your head to look around, you risk tensing facial muscles, and if you keep your eyes open, you may smile out of embarrassment, at the audiologist (I speak from experience!! frown.gif). Just relax, both muscularly and mentally, zone-out, and ignore everything for the 5 minutes it takes the silicone to cure.

 

On a personal note, I have often seen people saying that silicone CIEMs are more comfortable than acrylic CIEMs, but I disagree - I've had both types and I've experienced discomfort with both types - and when I had refits done for each type, they both were very comfortable. So don't choose silicone or acrylic on the basis of thinking that one or the other will be more comfortable - the thing that decides if a CIEM will be comfortable is not what it is made from but how accurate your impressions were, and, of course, how skilled the technician is at the manufacturer's workshop, when creating the moulds from your sent impressions.
 



Please chime in, anyone, if you have details additional to what has so far been discussed in this thread; it's a useful reference, IMHO.

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