Thanks, you are probably right. The more I think about it the less likely it seems. They are already doing a remarkable amount of monitoring and processing for such a small low power device and probably have a wish list anticipating the next generation of hardware.
They aren’t. They are really only asking for a particular gain at different levels at each frequency, and their compression ratios are just a consequence of that. They don’t speak to time constants–there’s actually not as much talk about time constants as there used to be. Perhaps in part because the industry has settled on what they thing is best for most situations, but also because there new adaptive technologies are doing a lot more stuff with them moment to moment. Some manufacturers still allow you to manipulate them a bit, but many do not.
When I print out the detailed settings of DSL v5 and compare them to NAL-NL2, I see the obvious reduction in compression ratio of the soft sounds from 3-4 down to 1.2. In the louder range CR seems to go down from 2-4 to about 1.7.
The first knee point for softer sounds seems to go up in DSL to about 47 at low frequencies compared to 40 for NL2. And for the second knee point DSL is at 62 compared to 55. However, I have no idea how significant or insignificant that is…
The other obvious difference is that the compression method (CM) used for DSL is Syllabic, while NL2 is Dual. My understanding is that Syllabic uses faster time constants, while Dual is slower. It does not seem definitive whether they are adaptive or fixed. I do see in the software that this can be overridden though. Not sure of the implications of doing that?
Compression and gain just co-vary.
I am not familiar enough with the Rexton/Signia hearing aids to be aware of that difference in time constants, but if that is true it is a manufacturer choice rather than a presciption choice. However, when DSL was initially developed I’m not sure adaptive time constants were even a thing–I’d have to check its history (history is not generally my strength, I prefer sci-fi).
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We’ll have to ask William Shatner. I know he uses a CPAP, but not sure about hearing aids. However at 88 the odds would seem good…
I found this PowerPoint presentation by Siemens on Understanding Compression which looks like it dates back to 2006. Here is one slide which seems to suggest they give a choice of Syllabic or Dual Compression and they are both adaptive. But, it is not exactly definitive and they never really define what Dual is. The software does give a choice if you override the defaults. Interestingly it is set on a channel basis, so conceivably you could set it differently across the frequency spectrum.
Haha. Shatner was famously one of Jastreboff’s tinnitus patients. I’m sure he must have hearing aids at this point.
I thought one of the adjustments that could reduce the problem of hearing distant conversations more loudly than desired was the kneepoint. But I don’t know how one does that.
As I understand it, the knee point is the point on the gain curve where it changes slope, usually to more compression. If the knee point was moved down, it would go to the next gain slope at a lower input sound level.
I made an appointment today at Costco to try the the DSL v5 formula. My fitter happened to be there and made the appointment. I am obviously her “best” customer as she does not even ask me my name. She even offered to do the fitting on Christmas eve.
Are you sure there isn’t more to this relationship than you think? 
I hear what you say, but all I need is a pair of hearing aids that work as well as they can. They are pretty good right now, so I will have to eat some crow if DSL messes them up…
Obviously my attempt at humor was weak, very weak. 
High compression helps with comfort but also hearing soft sounds. The NL2 formula generally prescribes higher compression settings as they are trying to maximize speech intelligibility.
This approach works well in quiet but breaks down in noise where the extra soft sounds amplification boosts noise arriving from a distance, and for non speech type signals like music where the compression kills important dynamic modulations.
Lower compression settings (or more linear settings) are often attributed to a more natural sound quality and may provide better performance in noise or in situations where soft sounds may be annoying. Music signals are also less constricted dynamically so less compression can help here as well.
A system that can modulate the compression is probably the ideal setup and for this reason a lot of manufacturers have adaptive compression systems.
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I got it and chuckled. But, she is married, as am I, and she is far too young for me. But, on the other hand, I am only 70, and when you are in the hearing aid fitting business, 70 might look pretty young compared to the usual crowd.
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Well we will see what it will do in a week or so. I am a touch worried about it as the sound of my aids is doing the best they have so far. So, there is a bit of a “if it ain’t broke, don’t fix it” thought in my head too. In any case I know how the software works and it is a few clicks to put it back to where it is now. No need for REM, and I could likely get it done by just dropping the aids off for a few hours.
As far as adaptive compression goes, I believe these aids have it. But, it only seems to apply to transients, with the attack and release time constants.
Are you describing the (comfort-clairity) settings?
Thanks
I am a few hours into using DSL v5 for a prescription. My gain may still be slightly high for my left ear which does not take to lots of gain very well. Overall the impression is that sounds are quieter and more natural sounding. There is slightly less bass perhaps. For sure there is more clarity in the high frequencies. I am hearing things I did not hear with the SmartFit/NAL-NL2 prescription (they were pretty much the same). The SmartFit seemed to give a real edge to certain voices on TV, and particular ones where the original sound quality was not the greatest. That seems to be gone. So far, so good.
I was getting a touch of feedback in my left ear, so I went up from a Small to Medium closed click sleeve, and it seems to help. I noticed when the fitter was doing the testing that my left ear was more sensitive to feedback. The no-go feedback zone on the screen was larger than the right ear.
Will be interesting to see how it does in different environments. Have not tried listening to music on my stereo yet.
Interestingly the fitter played with the gains on the left ear for quite a bit of time, and in the end had a curve that looked almost exactly like the one I produced in my first post.
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No I believe you are referring to sound recover2 which is frequency compression, a different feature altogether
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In the Phonak Target Global Tuning section there is an option to adjust the compression (gain compression) to semi-linear or linear. If someone wanted to try less gain compression that would seem to be an easy way to try it without changing the basic formula. However it changes both loud sounds and soft sounds compression. I was interested in changing the soft sounds, but not the loud.