Fitting Protocol Questions

Jennifer GrothIt was recommended to me that I could use Corfig as a fitting protocol.  How would I do this?

By Jenny Groth

CORFIG is not a fitting protocol. It is the coupler response for flat insertion gain. What that means is that it is a set of device specific correction factors that are used to translate measurements or targets from the real ear to the coupler or the other way around. So for example, Audiogram+ prescribes insertion gain targets. Let’s say that the targets were 20 dB at all frequencies for G50. If you wanted to do your verification in the coupler rather than measuring in the real ear, you could use the CORFIG corrections to translate the insertion gain targets to coupler targets. Depending on whether you are fitting a custom device, BTE or whatever, the CORFIG corrections will be different. You would add those on to the 20 dB insertion gain targets to get coupler targets, and then you could just measure in the coupler instead of on the ear. This is often done for pediatric fittings.

The components of the CORFIG are Real-ear-to-coupler difference( RECD) + Microphone location effects + ear canal resonance

On the Verifit, standard CORFIG values are used for the simulated speech mapping that you can do in the coupler instead of doing it in the patient’s ear. They will be a bit different than the specific ones we use for our products (you can get an idea of what the CORFIGs for any product are by switching between 2cc and simulated insertion gain view in Aventa). Because the individual patient will have variations in all the components of the CORFIG, this type of coupler verification is still an approximation and thus a step down in accuracy from real ear verification. But you don’t need the patient’s cooperation to do it. In fact, you don’t even need the patient at all. J The accuracy of fitting to coupler targets in this way can be enhanced by measuring the individual patient’s RECD and using that in the CORFIG corrections rather than the average one, which is often done for pediatrics but not really worth the bother for adults.

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