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Phonak Target: changing fitting formula changes estimated feedback threshold?

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Target 9.0; no ever connected for current client. For purposes of this observation, there are two groups of fitting formulas:
Group 1: v5a Adult; DSL v5a Pediatric.
Group 2: DSL [i/o]; the three NAL formulas; the two ADP formulas.

For a given coupling specification, changing from one formula in a group to another in the same group doesn’t change the estimated feedback threshold dashed red lines. But changing from a formula in one group to any in another group does substantially change the feedback threshold curves.

The same applies to the gray maximum gain curves.

Why would changing the fitting formula change the estimated feedback threshold or maximum gain – aren’t these estimates both entirely a function of hardware (HA and coupling) when no user/client response has ever been measured?

No replies in a month :sob:. I’d very much like to understand what’s going on here, as I think it would help me better understand fitting formulas in general.

Please read this and then ask your questions, truth be told I’m a little confused about what you’re actually asking but anyways here it is.

What is a Prescriptive Fitting Formula and Which One Should I Use with my...36

Prescriptive fitting formulas are extremely helpful in the process of fitting hearing systems. They help hearing aid professionals to develop a pre-adjustment for the hearing devices.

Thanks, but I had read that. Alas, I can’t think of a clearer way to ask than the last sentence of my OP, along with the question of how the “group” differs from the NAL-ADP “group” with respect to generation of the feedback threshold function.

Even with one fitting formula, click between programs and the feedback formula changes.

It seems really low in the lows for my Phone Call Program on my P70. I can’t change it so never bothered to find out why.

:slight_smile:

I shall watch this with interest, as the Phonak fitting formula doesn’t fit well with me. DSLv5.0 looks better for me.
Peter

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