Testing HAs for functionality and best practices - REM and Test Box question

I listened to a video of Dr. Cliff’s on his best practice of using a Test Box to test the functionality of HAs once they come into the office and prior to the first visit with the individual receiving them. Then the individual is fitted using Real Ear Measurements (REM) in the office… Is this process best practice? Or are there other equally valid ways of testing for functionality of the device from the manufacturer and using REM to get the best fitting for the HA per individual.

My experience:

The Costco HIS advised though they have a TEST Box they don’t use it. Instead they rely on REM’s - and only if there is an issue do they use the test box. They assume the HA is functioning properly from the get go. However they do use a REM test during the fitting for the individual and do put the “nodes” (sorry not sure of proper word here) in the person’s ear during the first appointment.

The audiologist I saw today doesn’t use a test box either. Instead their process is to use REM WITHOUT the individual present and set HA’s to the audiology test.They never use the REM with the individual because they said that it was difficult to insert the "node"in the ear and position them properly so they don’t give erroneous readings.

Are either of the above processes proper ways of going about this? And/or how “should” this process work?

I think you mean probes instead of nodes. It is impossible to do REM (Real Ear Measurement) without the individual present. The whole idea is to see how much gain the patient is getting in THEIR ears. Everybody’s ear acoustics are different so one needs to do REM to know how much gain they’re really getting. I actually think some people do a decent job fitting hearing aids without using REM, but lying about it is not cool in my book.

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So what exactly is the problem your having with your HAs, maybe like your not sure if your HAs are working correctly, even after having REM verification?

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I have a question: may be a stupid one. Why, if a hearing aid is shown to be delivering the required frequencies at the required gain in the test box, why would it not do so when placed in the patient’s ear immediately thereafter?

I mean … if I understand REM correctly, all it does is ensure that the hearing aid is delivering specific frequencies at prescribed gain levels just as it was shown to do in the test box.

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I agree. Apparently, it’s claimed that the shape of each individual’s ear canal effects the delivery of sound to the ear drum. Perhaps, but I’m still unclear as to how REM measures that.

My real concern with REM is that it may measure sound being delivered up to the eardrum, but most people’s hearing loss occurs in the middle or inner ear. REM doesn’t measure that. So, again, if the test box shows that a HA is functioning according to specifications…and if the variables introduced by the shape of each individual’s ear canal are minimal (I don’t know if that’s true)…then, is REM really just a bit oversold? is it really just a way of saying, yes, your HAs are functioning as they’re supposed to?

You run standardized tests in the testbox in advance to determine whether the brand new hearing aid is meeting specs. If you don’t do this, you are just trusting the manufacturer to not send you a lemon. The manufacturer sends out many devices and a certain percentage of those are lemons. Manufacturers have gotten better on their quality control, and I would certainly guess that this is an area getting squeezed out by increasing demands on clinical time, reduced margins, inflation, all the same old stuff. Sounds like your Costco doesn’t do this, unclear whether your audiologist does. A certain percentage of new hearing aids are lemons.

Real Ear measures > simulated real ear measures with individual RECD measures > simulated real ear measures with an assumed average ear canal. That is, there are aspects of a fitting that a testbox just cannot capture, but that you can improve but sticking in an individualized measure of the ear canal acoustics (which still requires that a probe mic be inserted into your ear at SOME point. You will still miss capturing exact venting, but some real ear systems do try to simulate those too now. It is very common to use simulated real ear measures with pediatrics because they are squirmy, but it is not best practice with adults who can generally sit still.

There is some minor skill required in properly placing a probe microphone I suppose but. . . hell, Costco is doing it.

Once real-ear is completed, there are some further measures that can be done in the testbox to confirm baseline function of special features so that malfunctions can be identified in the future. This is another place that is probably being squeezed, but again a certain percentage of directional microphones breakdown within the first few months and it’s nice to be able to catch that quickly (of course, this also depends upon patients attending their regular appointments).

Because the shape of your ear and the venting related to how the hearing aid fits in the ear impacts the gain that reaches the eardrum, sometimes a little and sometimes really dramatically. There are various corrections in the box that try to account for these things, but can only go so far. Testbox measures with a pre-measured individual real-ear to coupler difference may get very, very close with a completely occluded fit.

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So, I punched in an RECD at the end of the day today that, off the top of my head, went: -4, 0, 4, 6, 7, 12, 12, 14, 8, 16. That’s the degree in decibels to which this individual’s ear canal acoustics deviated from an average ear at 250, 500, 750, 1k, 1.5k 2k, 3k, 4k, 6k, 8kHz. This is a very common, standard ear, not at all an atypical measurement. So this is how far off the patient’s hearing aids would be from targets if fit in the testbox, before we even start talking about the impact of venting. A 12 dB deviation isn’t small beans to me.

I had a memorable patient a few months ago with ear canals only slightly on the larger side and the result of his particular ear canal acoustics were that the manufacturer “first fit” was basically inaudible for him at the frequencies that mattered, which explained why he had been to multiple clinics and returned their demo hearing aids over and over because he never noticed much benefit.

Yes. It definitely is. Don’t you think your clinician should confirm that your hearing aid is working the way it is supposed to? You paid a lot of money for it.

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Thanks for the explanation, @Neville. I was unaware that ear canal acoustics played such a significant role in determining what sounds get to the eardrum, however, thinking about it further, I think I can appreciate the principles involved.

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Is REM also part of the fitting procedure of ITE HA (ex. Phonak Virto half shell)?

Yup, all traditional air conduction hearing aids.

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[There used to be a blues dive I played in that had a “dead zone” - just because of the shape of that corner of the room - that not even my old Fender Twin with JBLs (and I don’t mean “Twin Reverb”) could penetrate, Twenty feet away, however, and it would make your ears bleed!]

@tenkan - Sorry, context is important. I am not having a problem with my HAs. I am looking to get my first pair and am trying to access not only audiologist/HIS practices so I know who to work with, but also my own knowledge about the process.

@Neville - Thank you so much for the very clear explanations above! That’s very helpful info as it furthers my understanding of not only the Test Box and REM, but also the issues some independents and maybe even some Costcos regarding time etc.

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It’s obvious to me, now, what has become of all the analysts and engineers made redundant by the previous administration: they’re all looking into buying hearing aids!

[As my grandmother used to say : “Elephantum ex musca facitur .”]

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That’s nuts. Acoustics can be weird. My brother sat in as the audience when they were completing the final acoustic tweaks on the local opera house, which they needed to do with a full house, and said it was very interesting.

Tough to be an acoustic engineer these days, I think. If you’re not the one guy building opera houses, no one wants to pay the (sometimes high) costs to create great acoustics in regular buildings. I wish they would though.

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@Neville: I’ve learned in the years sine that it was probably just phase cancelation from the weird reverberations of the place …

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Think of all the senior living facilities with big high ceilings and people cannot hear each other in the dining room!!!

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Yes, it’s awful. Wouldn’t it be nicer if they were built with acoustics in mind. I have a friend who just built a new home with a huge open combo livingroom kitchen dining room, high cathedral ceilings, goreous wall of windows looking out onto the lake. But the acoustics are noticeably aversive even for normal listeners and if the television is on no one can hear anything.