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Differences between NAL-NL2 and Adaptive Phonak Digital

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I currently have Phonak Brio 3s set up with Phonak Adaptive, and am on a first fit trail with Costco KS9s – initially set up with the NAL2 fitting algorithm. I find the Phonak Adaptive much more natural and comfortable, yet do accept that I’m picking up some speech elements better with the NAL2, though overall the sound is thinner and scratchier, with a lot more emphasis on the high frequencies. So my question is, in theory, if the fitting software was used to plot a middle ground between the 2 sets of curves, would it matter which algorithm you start with – will the middle ground be identical? Put it another way, is there anything else going on in the different algorithms other than adjusting the gain in each individual frequency for each of the 3 gain curves?

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Edited

Providing the fitter is prepared to take the time to do it it should be possible to manually split the difference between two formulas. Formulas differ in the shape of the three gain curves as well as in the amount of compression used which is the difference between the soft and loud sound gain. Here is what I see for you loss and a prescription. I find NL2 to be a fairly smoothed out correction, perhaps designed to accomodate older hearing aids with fewer adjustment handles? Don’t know.

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My software is Rexton so I can’t produce the Phonak Adaptive curve. Here is what Rexton call SmartFit which is their proprietary formula. You can see it tries to follow your loss more closely rather than smooth out the gain vs frequency curve. Each manufacturer gets to design their own curve, and may employ different philosophies. One knock I have seen written about the propitiatory curves is that they may be less corrective to promote more easy acceptance of the aids for new users. SmartFit does not seem to follow the approach, and my observation is that their curves are more aggressive if anything. No idea what Phonak is like… What I see here is that SmartFit is boosting the mids more and the low frequency less than NL2.

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Oh, are you using double domes? It looks like without them feedback could be an issue.

Depends on the manufacturer. Prescription in most cases changes the gain and compression, and you can theoretically re-adjust one prescription into another one. But some manufacturers do some extra things and keep it in their proprietary algorithm only, so you may be better off setting the software to their proprietary algorithm and then adjusting to a different one with to maintain, say, oticon’s floating linear speech window. Phonak is generally not like this unless you want the slow attack/release times hidden away in the phonak contrast fitting, which most people don’t.

There’s always a fight between “natural and comfortable” and “maximum intelligibility”. Keep in mind that your brain is flexible. Typically, if you push towards intelligibility it will become more natural over time. (Presuming that the hearing aid is fit appropriately and there isn’t just something super wacky going on with the gain settings.)

@Neville said:

There’s always a fight between “natural and comfortable” and “maximum intelligibility”. Keep in mind that your brain is flexible. Typically, if you push towards intelligibility it will become more natural over time. (Presuming that the hearing aid is fit appropriately and there isn’t just something super wacky going on with the gain settings.)

Absolutely true. Go for best speech understanding and it will sound great in a few weeks.

In reply to @Neville

So in general are you saying that you use or -v5.0 when programming Phonak instead of Phonak Adaptive? It seems like so many audiologists/fitters have been sold on “the manufacturer knows best.” Although it sounds like that might be true for Oticon.

I never use phonak adaptive. I sometimes have good outcomes from phonak adaptive contrast for Meniere’s or severe/profound patients. But because I am performing , I’m always adjusting against independent targets anyway.

In reply to @Sierra

Thanks for the detailed overview here, it is very useful in visualising what is happening. I am using , with 2 tiny vent holes, and yes, my first 2 weeks with the KS9s have been plagued with feedback problems. I only just realised, but at my first fitting, the feedback manager was not run. At my 2nd, I had to suggest we run this, and this seems to have cured the feedback. However, on the charts, I notice that huge chunks of higher frequencies have been taken down by the software. I’m now quite a long way off prescription, so am concerned my set up isn’t as good as it should be. I’ve been sent on my way with no follow up booked, and am not entirely happy at the moment. I’m assuming that molds may be needed to get me up to prescription without feedback, or would a more powerful receiver also help? Luckily I have the Costco return option to fall back on if all else fails, but I’d really like to get these working as they should.

That was my experience with a trial of Phonak Marvel 90. They ran the feedback manager and wanted to cut out a bunch of high frequency gain. I declined. Feedback was bad with vented domes, but then I switched to larger domes and the feedback all but disappeared. You might want to try larger domes or custom molds.

In reply to @WestEndBob

There should be double domes or perhaps power domes to try at no extra cost. I would do that first, and if that is not good, then try molds. They have a money back guarantee on the molds too.

As for follow up appointments, I do not wait for them to invite me. I make an appointment whether they offer or not. Have not gotten any push back. That is part of the price of the aids, unlimited follow up adjustments.

In reply to @WestEndBob

In my experience, losses greater than 40dB at 2000Hz will not meet target gain in Real-Ear if the patient has been fit with open domes. And if they do hit the gain curves, there will be issues with feedback. So, I will fit with either or custom molds. Very few patients are actually appropriate candidates for true domes.
The other downside to open domes is that you lose the benefit gained by having directional microphones. Directional mics give you about a 3-6dB (signal to noise ratio) improvement. Yet, you lose about 3-6dB of gain by having a truly open fit. So, consider closed domes or custom molds!

Wearing hearing aids is like getting physical therapy for your brain. It can takes weeks or months to retrain the brain how to hear and process sounds. It won’t sound “natural” because your brain is used to being deprived of those sounds. It has gotten used to your hearing loss. Reintroducing all the sounds you have been missing can sometimes be a bit of a shock to the system. Comfort is important, but the end goal should be audibility. I perform Real Ear Measurements to see where my patient’s targets should be (based on , NAL-NL1 or algorithms), but then will use the adaptation manager to slowly build up to those goals over an appropriate amount of time. Everyone adjusts at different rates. However, you will adjust more quickly if you are wearing the hearing aids for more than 8 hours per day, every day of the week. Like with physical therapy, you will get out of it what effort you put into it. Best of luck to you!

@drlaura said:

I perform Real Ear Measurements to see where my patient’s targets should be (based on NAL-NL2, NAL-NL1 or DSL algorithms)

How do you choose among those three? (Please be gentle; amateur/user attempting self-education.)

I’m happy to explain! :slight_smile: 5.0 is used for pediatric fittings. The purpose of NAL-NL1 is audibility/clarity and is comfort. For older first time users who cannot tolerate NAL-NL1, I may use NAL-NL2. For power junkies, patients complaining of clarity issues, or younger hearing aid users NAL-NL1 is my go to. I’ve worn a lot of different hearing aids from a lot of different manufacturers. Their proprietary algorithms vary. I’m a bit of a power junkie myself (and my hearing loss fluctuates). My personal preference for my own hearing loss is NAL-NL1. Hope this helps!

In reply to @drlaura

It helps a lot! My current Phonak V90s were fit with Adaptive Phonak Digital, which I’d bet is an attempt to maximize the proportion of new users who evaluate their first as acceptable or better. But I’m going to switch to the Costco KS9 or possibly Marvel M90 very soon, and based on your description I’d say I’m an NAL-NL1 candidate. I’ll be interested to see how my Costco reacts to that suggestion tomorrow.

What I typically do for my Phonak fittings (or most manufacturers), is I run Real-Ear at 100% adaptation level in the manufacturer’s proprietary algorithm. If it is not too far off of NAL-NL1 targets, then I will leave it in the “Adaptive Phonak Digital” settings, but adjust gain to hit NAL-NL1 targets. If the Adaptive Digital settings are eons away and it’s going to take a huge amount of tweaking to get it to hit NAL-NL1, then I will straight up change it from “Adaptive Digital” to “NAL-NL1” settings, which should get me closer. I keep a close eye on my compression ratios though. You don’t want them to over 1.8 (and definitely not over 2.0 or you can get some distortion with sound quality). Some providers may run , but that does not mean that they necessarily use the formulas to hit targets. Or that they’re proficient at adjusting the devices. And hearing aids are only as good as the person who programs them. So, my advice to you is: shop for a provider, not a device. You can buy a hearing aid just about anywhere these days. But you want to get a provider who really knows what they’re doing when it comes to programming. Best of luck to you!

In reply to @brec

I don’t have the Target software so can’t model the Adaptive Phonak Digital for you. Here are some of the others. What I find is that these prescriptions cannot really be generalized that much. They “react” differently for different losses. What the formula does for you can be quite different that what it does with a different shaped loss.

NAL-NL1: This formula is the earlier version of . As you can see the low frequencies are attenuated somewhat, while the midrange has the most gain. It also has the most compression, which is the difference between the top (soft sounds gain) and the bottom line (loud sounds gain). The high frequencies are kind of rolled off and have no compression. You may hear that as a loss of the detail and the air, as you need a fair bit of gain there.

image

NAL-NL2: This is the updated version, and is more commonly used. Notice that it is a smoother gain across the whole frequency range from 500 Hz up. There is also a lot of compression used from 500 Hz up. This one should sound more lively and brighter than NL1 in my opinion. It can be set for child or adult, as well as for tonal and non tonal. Tonal is apparently used for those speaking Asian languages where the same sound at different frequencies apparently has a different meaning.

image

v5: I have to disagree a bit with DrLaura on this one. While it was originally developed for children it has been updated a long time ago to have a correction for either children or adults. It is currently on version 5 of the updates. This one has a steady increasing gain vs frequency with the most gain of the three at the highest frequencies, It also has the least compression. Soft sounds are not going to be amplified as much, and loud sounds amplified more, although the compression reduction is more on the soft side of the normal sounds.

image

I have an appointment at Costco for next Friday and I am going to give DSL v5 a try. I am currently using the Rexton proprietary SmartFit which is fairly similar to NL2. It is pretty good, but I am annoyed by distant sounds seeming to be too loud. For example if someone flushes a toilet in the bathroom down the hall, it sounds too loud to me, and competes with normal sounds in the room I am in. It may be a big bust, but I am going to give it a try.

In reply to @drlaura

“Shop for a provider” is certainly the consensus top advice among pros. But it’s tough: how to do this shopping? E.g., how do I interview a variety of Costco fitters, and what do I ask them? (Costco has a huge price advantage. I guess I could think about spending 300% [$4,500] more for a top-notch provider if I could find one.) After tomorrow’s Costco appointment I do have appointments on Mon. and Tues. with independent providers; if I’m persuaded (somehow) of their competence relative to the Costco one’s I hope one of them will accept an unbundled deal. Bundling (charging $5000+ for a pair of aids with lifetime service) makes no sense to me; I might move hundreds of miles away in a year.

And back into the weeds… why start your Phonak fittings with the proprietary algorithm and then use NAL-NAL1 standards to adjust or evaluate it? Why not just start with NAL-NAL1?

In reply to @Sierra

I frequently have adult patients using 5.0, but most of them are patients who have had hearing loss identified in childhood and have been hearing aid users for years. It can be very difficult to transition these patients out of the DSL algorithm once they are grown (they don’t want to suddenly stop using DSL just because they turn 21). So, I did not say that DSL cannot be used for adults, but it is the algorithm most commonly used and widely accepted for hearing aid fittings for children.

In reply to @brec

A good place to start when deciding on a provider would be to find out if they follow evidence based practice and follow best practice guidelines. Dr. Cliff has a great checklist available on his website. It can be found by following this link here: https://assets.website-files.com/5d9aadca574a7d240f2c7327/5dc22dcb06c33a18fd9fe31d_Dr.%20Cliff%20AuD%20Network%20Best%20Practice%20Checklists.pdf47
Paying more for hearing aids only makes sense if there is more value added to what the provider is offering. I agree that bundling does not make much sense for most patients, which is why my own practice is unbundled. I practice in Florida, where a great number of my patients are tourists or snow birds, so when creating my practice model, I really could not justify charging for potential appointments that most of my patients were never going to be able to take advantage of. My prices for the aids are based on what manufacturers charge me, and the cost for my service depends on the time and complexity it takes to perform the task.
I’m afraid that the easiest explanation I can give you is that programming hearing aids is both an art and a science. It takes years of study to understand the science, and years of experience to understand the art. Every patient is different and may require me to approach their fitting from a different angle to achieve the desired outcomes. One standard from which I will not waiver though, is in running Real-Ear itself. I have to know what the desired target is, in order to move the patient towards hearing to the best ability of which they are capable. You may find that many professionals differ in their approach to programming, but one fact will remain the same: currently, there is not a way to accurately, independently verify what is happening in the patient’s ear canal without running . So, if you fit hearing aids without Real-Ear measurements, then you are just guessing that the device is doing what the patient needs it to do.

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