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NAL-NL2 vs SmartFit and Real Ear Measurements

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Edited

In reply to @Don

@Don said:

Did you mix up the pictures because the second has higher gain for soft speech at 1k, 1.5k, 2k, 3k.

Yes, you are correct. I didn’t have the images mixed up, but I had loud and soft interchanged in my head. The labels got cut off and I forgot which was which. In general the seems to emphasize those frequencies, and the SmartFit formula is more conservative.

I have done a little more work on this potential choice between prescription formulas. I plotted what I think are the insertion gain targets (from Connexx8) for the soft, medium, and loud levels for both ears, using both (Experienced) and the proprietary SmartFit (Power) methods.Some observations I made:

  • The NAL-NL2 method seems to use a fairly consistent wide spaced gain between the soft, medium, and loud inputs. The soft are amplified the most and the loud the least. I am understanding this to mean there is fairly high compression as soft sounds are being boosted, while the loud ones not so much.
  • The NAL-NL2 wide spaced compression gains are quite smooth and consistent between the left and right ear, other than for the overall gain. It seems a high degree of smoothing is used.
  • The SmartFit uses less compression and at certain frequencies almost none. Linear gain? I would presume that would mean the original dynamic range in sounds is more preserved.
  • The SmartFit method seems to attempt to follow my hearing loss more closely across the frequency range, rather than smoothing it out.
  • The roll off at higher frequencies is much more significant with the NAL-NL2 method.

The differences between the prescriptive methods seem significant and I would think there would be an audible difference. What are your thoughts on how they would sound compared to each other?

LeftComparison

RightComparison

I had my ’s fitted today, and I was not impressed. Essentially what I was told is that they use Connex 8 to set up the hearing aids and they use the SmartFit prescription as a starting point, but legal requirements for our province (Alberta) require them to do with . She more or less said they had to do it this way so they get part of the cost of the HA back from Alberta Health care, similar to the issue in the US. Then she said to try them and they can work with further tuning (after they get their money, which is really my money). But bottom line is that they are not using AutoFit, and the fitter was unaware that AutoFit could be used with SmartFit. I got the strong feeling that it was simply not the Costco way! She said that there was not much difference between SmartFit and NAL-NL2 formulas. Obviously not the case.

But how are you hearing?

I had not been aware that Alberta had provincial rules for hearing aid benefits stipulating that verification must be done. That’s fantastic. The policy does not stipulate targets; I’m sure any independent prescriptive targets would be acceptable. SmartFit is, as mentioned, not an independent target. I wouldn’t fault Alberta for requiring evidence-based practice.

I have a significant problem with certain frequencies at moderate to loud amplitudes in the left only. I plan to do some testing with some tone recordings I have that I used to balance my stereo speakers to see if I can identify the frequencies that are a problem. It sounds to me that when I hit a certain amplitude frequency point the sound quality goes to total trash noise - breaking up. Other than that they are kind of OK for sound quality. I am not sure if the receiver is being over driven and is breaking up but that is what it sounds like to me. I suspect that if my ear is being over driven that it does not sound like what I am hearing. I don’t recall any sounds like that when she did the threshold testing for the .

I am not so impressed with the process they used. It seemed to me that they were just doing it to check the box needed to get the government rebate processed. I really have no idea what I have now for a target curve as they started with a SmartFit and then manually tweaked to a . When I complained about the breakup noise in the office all she did was manually reduce the gain in a higher frequency range which I am guessing was in the order of 4-5 kHz.

You are hitting 90 db hearing loss at 4k on the left. Things may never sound great right there (4k on the left) but if you feed it sound it could become clearer after a while (months).

Actually they seemed better today. I listened to some music on my stereo at a fair volume and did not hear any distortion. Perhaps it just did not hit the sensitive frequencies… I ended up with M receivers and re-ran the Connexx software based on Power SmartFit and . They don’t seem to be anywhere near the maximum output limit of the M receiver.

SmartFit Power

FOG-M-SmartFit%20Power

NAL-NL2

FOG-M-NAL-NL2

I tried on P1 and the Oticon proprietary formula (Oticon OPN1) on P2 some 8 weeks ago.

I consistently found that NAL-NL2 program gave me better speech understanding (subjectively) than the standard Oticon formula.

As a result, I am using NAL-NL2 as my default program.

I haven’t got access to my software to show differences in prescription between the two as I am away from home on an extended vacation.

I will report again when I have my Audio do the follow-up corrections with for both.

Hope this is not too far off the thread subject of Cosco aids.

I’m trying Adult and I like it. Hi frequencies were set higher but lower frequencies were a little lower. was way high.

So I lowered MPO 9db and raised soft Sounds 2db. Everything is clear and I can hear soft voices.

In reply to @Sierra

There is a pretty good but getting old thread discussing the various fitting formulas. Here’s a link to the 2nd comment rasmus_braun made in the thread (see also his previous one above in the referenced thread):

Fitting Rationales: VAC+ vs. NAL-NL1, NAL-NL2 or DSL v5.0a
I think it depends on what your goals are. If you want a very natural and comfortable sound quality, then the proprietary formula will likely work well. But if you want the best audibility of speech, NAL and DSL are both proven approaches. I would suggest that you try a verified (using REM) fitting with NAL-NL2 or DSL v5 and see how you perform on a speech-in-noise test, and then compare it with the proprietary formula.

In reply to @jim_lewis

BTW. I asked my audi today her take on what the difference was between the ReSound proprietary + (based on ) and the NAL-NL2 & algorithms.

She said there is more compression in Audiogram+ vs. the other two algorithms and likened it to the difference between progressive bifocal glasses vs. straight bifocals (no gradation). She said with Audiogram+, there’s more of a gradual bump up in gain as the volume changes whereas with the other two “it all jumps up,” which might be too much for some people.

Don’t know the rightness/wrongness of her analogy but I thought I’d offer it for discussion and hopefully learn lots of additional good stuff from you all in the process if there’s anything right or wrong in her comments worth discussing.

Edited

Don’t know the rightness or wrongness of more compression - but I did think she was telling me that + was designed to be more comfort, fewer returns from users - but the best thing she told me is that if I wanted to be a ’er and fire away substituting or for my fitting, as I told her, was to go for it - that she was happy to have me experiment and actually wished the opportunity was available to more users (maybe less follow-up work, less “free fittings” by the provider? - but I shouldn’t be cynical - she a marvelous audi at least as far as customer relations go and I’m glad that I got hooked up with her - particularly after getting a thumbs up for DIY’ering (or whatever!)-particularly that if I stayed within the limits of the fitting software guidance on switching algorithms, etc., that I was unlikely to damage my hearing.

Update:: Here’s a ReSound Blog discussing NAL-NL2 vs. Audiogram+ (not meaning to take discussion too far off topic of NAL-NL2 vs. SmartFit). Perhaps both my audi and Don are both correct. The blog basically says as a “first-fit” Audiogram+ is designed for user comfort and found to require somewhat less fine-tuning after the initial fit than NAL-NL2 for user satisfaction. But also seems to be saying Audiogram+ tries to avoid too much gain, Audiogram+ compresses everything DOWN whereas NAL-NL2 is flatter with more gain allowed across the range of amplification (my experience from looking at my target output curves). Says no matter what the algorithm there are problems arising at the ideal fit that satisfies the user (fine-tuning required, doesn’t mention ). There is some discussion of NAL-NL2 vs the NL(1) version. The blog is from 2014.

A NAL NL2 and Audiogram+ Showdown!24

It is probably hard to generalize the manufacturer formulas. They may all take a different approach. When I compare the SmartFit Power to there are some obvious differences. The NAL-NL2 is smoothed out. So there are areas where it under corrects compared to SmartFit, and other areas where it over corrects. SmartFit follows the hearing loss much more closely. And in general the NAL-NL2 boosts the quiet sounds more and the loud sounds less. In other words more compression.

OK, I have had my aids checked by my Audiologist on for P1 and Oticon VAC+ for P2.

The REM check showed that I was very close on my fitting with my adjustments. So that the new fitting results are very much the same as I previously had.

Therefore I am sticking to NAL-NL2 for better speech intelligibility (at least for now!).

and are both evidence-based prescriptive formula with slightly different ideologies.

Manufacturer fits are secret mysteries, mostly based on some version of NAL, but must in the end be driven by patient acceptance rates.

@member45 said:

OK, I have had my aids REM checked by my Audiologist on NAL-NL2 for P1 and Oticon VAC+ for P2.

But both checked against NAL-NL2 targets.

Okay, I have a sort of dumb question;

Am I correct in my understanding that is performed AFTER acclimation to ’s?

I’ve had my HA’s for about 5 weeks now & My audi has REM available, but hasn’t done it yet.

When should I be pushing to have REM done?

Dave

Edited

In reply to @Neville

@Neville said:

NAL-NL2 and DSL are both evidence-based prescriptive formula with slightly different ideologies.

@member45 said:

OK, I have had my aids REM checked by my Audiologist on NAL-NL2 for P1 and Oticon VAC+ for P2.

But both checked against NAL-NL2 targets.

No Neville, NOT BOTH checked against .

My aids are set as follows:

  1. Program 1 is “General” programmed to NAL-NL2 target and corrected with to NAL-NL2 target; and

  2. Program 2 is “General” programmed to VAC+ target (Oticon) and corrected with REM to VAC+ target.

That allows direct comparison of fitting rationales with “the flick of a switch”.

Genie 2 Programming allows for different programming rationales on each Program setting.

I was just confirming my preference for NAL-NL2 for superior speech ineligibility over VAC+ after I had my Audiologist do the REM testing and verification and necessary adjustments for each Program on my aids.

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