Differences between NAL-NL2 and Adaptive Phonak Digital

There is a huge difference in the prescription when you click the Child button. instead of Adult. Adds way more gain, and compression. It may be the result of other issues. I’m guessing that most children do not have the high frequency ski slope loss like us old guys. Perhaps the Child formula is not intended to deal with a ski slope loss.

@Dusty directed me to the Phonak Target 6.1 software, and while I am still fumbling around with it, here is what I see as a first fit with Adaptive Phonak Digital, M Receiver, and Power Domes. The dashed magenta line seems to be the feedback threshold, and the recommended gain puts you into trouble at high frequencies. It would seem that custom molds would be in order. In comparison to the previously posted prescription formulas the Adaptive Phonak Digital seems to be most similar to NAL-NL2. Smoothly increasing gain from 500 Hz with quite a bit of compression. I checked what optional programs are available, but it just shows the Marvel M90 ones as I do not have the KS9 connected. To see what the KS9 offers I assume you would have to have a pair connected to the software.

And, I see that by default the Target 6.1 wants to use frequency compression. I would discuss the pros and cons of that with your fitter. I wouldn’t do it. The ideal way would be to try it with and without.

Child targets are about 7 dB higher (on average) than adult targets. Children cannot use top-down processing to fill-in-the-blanks like an adult can because they have not learned language, so DSL child targets were developed to maximize auditory access. If a provider were trying to transition someone out of child targets and into adult targets simply because they had grown up, that provider would likely be ignorant of the history behind the development of the different precriptive targets. Adult targets aren’t lower because it is better for them to have less gain, they are lower as a compromise for what people will generally tolerate. While there are certainly a bunch of caveates to this, so long as hearing aids are not set at a damaging volume, users who can tolerate more gain generally do better than users who cannot.

People think of DSL as “pediatric” because it was developed first as a pediatric target, and because NAL does not have pediatric targets so if you are fitting kids you have to use DSL. DSL adult targets are just as valid as NAL adult targets; the basic ideals behind the fitting rationals are just slightly different.

@Neville said:

People think of DSL as “pediatric” because it was developed first as a pediatric target, and because NAL does not have pediatric targets so if you are fitting kids you have to use DSL.

The Connexx software does have a Child setting for NAL-NL2. It does seem to boost gain about 7 dB, and increase compression.

What power of a receiver are you using? The gain limits seem low. I believe the software picked Medium and that is what my graphs are based on.

I believe the Compression box at the bottom refers to gain compression, not frequency compression. If you change it to linear it should just scrunch the soft, normal, and loud lines together.

For the audiogram, I just used the one that pops up when I click on your avatar.

It appears your gains are being significantly attenuated to avoid feedback, even in the left ear.

My receivers are S/Standard. The alternatives are P/Power and SP/SuperPowerplus.
I updated the audiogram that pops up since you first used one, in case you saved that one. I’ll be getting a new one today.

There should be a M or Medium between the S and the P power receivers. I think the S receiver may be a little underpowered for your loss.

Thanks, I’ll check out the Feedback and Real Ear issue when I go back. I suspect you’re right. What’s the solution? Skip the test, and then guesstimate what feedback suppression is needed – e.g., closed domes, custom molds?

I tried the different options and the power domes seem to give the best feedback protection in Target. In the Connexx software custom molds with 2.5 mm vents seem to improve things. Not familiar with this software so don’t know if there are any other options…

Thanks for taking the time to lay out some guidelines that integrate science, art, economics & ethics in practice. While I have no hearing loss provider training, some of these elements are present in being a good practitioner of any field. Dr. C’s instrument looks like a great organizer for a provider to make sure they have covered the variables. I’m unclear though how I as a beginning HA consumer would utilize the checklist to decide on a good provider, as it would seem that I would only know if they truly step through all that list with my care AFTER the fact. You & others on this great site stress that REM is non-negotiable & that one element is easy enough to ask up front (which I did when I first connected with COSTCO staff). I’m trying to imagine taking a copy of the multi-page checklist with me & asking them at first meeting - will you do all these steps with me? How would you suggest a consumer might use the checksheet to screen potential providers at the front end of the provider selection? Thanks in advance.

@brec said:

didn’t like the compression of NAL-2. I went back to DSL.

Brec, please elaborate the differences in compression. Thx.

NAL-2 has more compression. That means the difference between the loudness outputs for the loudest and softest inputs is smaller. So softer inputs are, for me, amplified too much relative to louder inputs.

What compression ratios do you get with NAL NL2?
My KS9s, Costco’s version of Phonak M90, are fitted to NL2. The compression ratios are approximately in the range of 1.2 to 2.0.

For my M90-312s–

The compression ratios are the very bottom line, somewhat hard to read in gray “ink” – but they are “>3” at all frequencies above 1.5 kHz.

For comparison, here’s DSL:

Because these are output rather than gain curves, you can visually see the degree of compression by the closeness of the red or blue curves to each other.