NAL-NL2 differences between Oticon and Resound

Hearing Aids
#1

I currently use hearing aids from both Oticon and Resound and both are fitted to the NAL-NL2 prescription formula. However, I’ve noticed that these hearing aids have different gain targets, especially in the higher frequency range

Gain target Resound (dotted line):
image

Gain target Oticon (dotted line):
image

As you can see Resound shows a more curved gain target compared to Oticon. Somehow Oticon has a higher gain target in the higher frequencies.

I’m curious about why there’s such a significant difference in gain targets between these two brands, given that both are following the NAL-NL2 prescription formula. Shouldn’t NAL-NL2 result in similar gain targets regardless of the brand of hearing aid?

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#2

Manufacturers use the standard algorithms but put slants on them. How they work best with the specs of ‘their devices’
Also take into account the coupling - the type of dome or mould you have. This changes the targets in the software. Each manufacturer has their own calculation of the ‘effective venting’ of their domes. Even if you have an ‘open’ dome from both manufacturers they might have different ‘effective venting’ and manufacturers might use this to influence the NL2 algorithm in different ways
Do you have a more powerful receiver on the Oticon aid?

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#3

how did you test your hearing? Did you use an audiogram?

did you also use IN-situ measurement?

When I look at your pictures where the frequency amplifications are, I am a little surprised that there is such a big difference. For example, if you insert an audiogram that is made in the clinic, then it will not be the same as in the hearing aid. If you do it IN-situ then the amplification will be as it suits your hearing.
Or maybe I’m looking at something wrong and concluding.

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#4

also with the Resound, I see the upper right gray field, which makes me conclude that it can’t amplify as much as the Oticon. Maybe you should use a stronger receiver and only then compare?

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#5

I use Oticon and Phonak with NAL 1 and they are also very different.

REM got them matching tho.

Not sure why the difference when venting and all all other settings are the same.

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#6

I have tried both the 85 dB and 105 dB speakers in Genie 2 with various dome settings. All result in the more or less same gain target. I’m unable to replicate a more curved gain target similar to Resound with Genie 2. It seems that Oticon really amps up the higher frequencies compared to others. Interesting.

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#7

This must be the explanation. But it sounds illogical to me. Having a standard algorithm like NAL-NL2 should result in more or less similar gain targets.

As written in my post above I have tried many different combinations and none of them changes the gain target into a more curved line.

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#8

Did you specifically select NAL-NL2 to be the prescribed fitting rationale in the program that is showing the gain curves above? It doesn’t matter if your HCP adjusted your gain curve to fit an NAL-NL2 target, if the program you’re looking at has the proprietary fitting rationale chosen, then the prescribed target gain curve you’re looking at would be based on THAT fitting rationale, not the NAL-NL2. You can’t just assume that just because the HCP did REM against NAL-NL2 that what you’re seeing now is the NAL-NL2. It must be select as such in the programming software in the first place.

Just want to get this clarified so that we can rule that out first before making any kind of analysis.

#9

My sincerest apologies! I thought Resound was NAL-NL2, but it seems I was too tired yesterday. Upon rechecking everything after your post I found out that the Resound gain target was NAL-NL1.

When inserting this in Genie 2 I get the same curved gain target:
image

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#10

Glad to hear! I hear that clinicians tend to do REM adjustment to NAL-NL2 targets, from a conversation I had with @Neville. It makes me wonder when REM is done whether most clinicians would ask their clients which fitting rationales they would like to target to. But then I can understand that it’d be too much of a technical question to ask a typical client in the first place. I wonder how they choose which fitting rationale as the target. I’m just guessing here that NAL-NL2 is more recent than NAL-NL1 (but I can be wrong, they may just be different). But if that’s the case, I wonder why a clinician would pick NAL-NL1 over NAL-NL2 to do REM on?

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#11

I cam across this snippet from Research QuickTakes Volume 6 (Pt. 2): Hearing Aid Fitting Toolbox—Verification and Validation. Not sure how relevant it is to the discussion.

Once a hearing aid company has licensed the NAL-NL2, they are allowed to make alternations, and can still call the algorithm “NAL-NL2.” What has been common practice over the years, therefore, is for most if not all manufacturers to alter the NAL algorithm to more closely resemble their proprietary fitting—that is, significant gain reduction in the higher frequencies, especially for soft inputs, beginning ~2000 Hz. It’s common that this reduction is 6-10 dB or more. Hence, while the fitting screen may show a “fit-to-NAL” it is not a fit to the real NAL, and it is unlikely that the patient will not experience the same degree of benefit.

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#12

NL2 is the standard as you said but sometimes it’s best for the wearer to use a different formulae. Depends on their history, and also factors such as the shape of the hearing loss

#13

Doesn’t Genie 2 pick a fitting rationale based on the intake questions (“Personalization”)? I get the impression that experienced users with heavy losses get NAL-NL2 while the inexperienced with light losses get VAC+.

And a good question! I’m wondering the same. This was done by an experienced audiologist in an academic hospital. The only reason I can think of is that I was using power domes, so REM-NL2 would be more prone to feedback due to more enhancement in the higher tones

#14

Wow, I did not know this. Kind of annoying because as a consumer, you have no knowledge whether you have a “real” NAL-NL2 prescription or not.

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#15

Is that by choice or by the software?

For my Oticons, it automatically gave me VAC+ and my Phonaks, it automatically gave me APD 2.0.

I’ve had both mine changed to NAL 1.

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#16

Software.

Why NAL-NL1 by the way?

#17

Why NAL 1?

It gives me better Speech in Noise and better Bluetooth streaming Altho since my hearing dropped, background noise is so muted that I probably need to look into changing fitting formulas.

I don’t have any fancy features on like NoiseBlock and what ever it’s called with Oticon. All features are turned off.

Since hearing dropped tho, background noise is so extremely muted tho I don’t like it even when all the fancy features turned off.

Speech is also extremely muted now since hearing dropped.

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#18

The manufacturer will almost always pick their own proprietary fitting rationale for their hearing aids over the standard rationales, because they think that their own rationale works best on their hearing aids. Otherwise, they wouldn’t bother coming up with their own in the first place.

The Personalization intake questions affects various settings inside Genie 2 but not the selection of the fitting rationales. The characteristics of the different fitting rationales is very subjective, so one cannot really make a hard definition of what the rationales are like in order to assign the personal preference to a rationale. For example, if you say you like bright sounds, how would Genie 2 know to if it picks NAL-NL2 for you that that rationale would be bright enough for you? What if you find DSL v5.0 Adult brighter than NAL-NL2 (which I personally do), and Genie 2 still picks NAL-NL2 for you? It’s better for Genie 2 to stick with VAC+ and increase the brightness control (the higher frequencies) gains than to arbitrarily decide which rationale is “bright” to your taste.

Note, however, that even if you have VAC+ in your default P1 General program, if your HCP makes REM adjustments for you based on an NAL-NL2-based target, then your REM adjusted gain result will now sound more like the NAL-NL2 rationale than VAC+, even though its base fitting rationale is VAC+ based.

That “can” be part of the reason why HAs seem to show to be “underperforming” when REM is done. The proprietary VAC+ (or whatever it is) rationale may not be designed to sound as bright as NAL-NL2 by design. So if your HCP tries to match a VAC+ based gain curve against the NAL-NL2 target curve, the VAC+ based gain curve may show to be underperforming in the highs compared to target, not necessarily because the Oticon HAs are bad and can’t amplify up-to-snuff per se, but it could partly be because the NAL-NL2 target curve is already stronger in the highs compared to the VAC+ target curve simply by the nature of its design.

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#19

The default formula can be changed in most manufacturers software I believe.

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#20

Yes, that’s true. It applies to Oticon Genie 2 as well. If you go to Preferences → Fitting defaults, you can change the default to NAL-NL2, for example. Then for a brand new client, the default General P1 program will show up with NAL-NL2 selected.

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