Conversion of Nucleus (Cochlear Corporation) current level (CL) units to microamps.

The conversion from m A to Cl and vice versa is different between the CI22/CI24M/R family implants and the CI24RE (Nucleus Freedom) implant. All Nucleus Implants have a logarithmic current law as to ensure an increase of a certain amount of CL is always a multiplication of the current, in other words, a change in CL can always be linearly transformed in a current increase on the dB scale.
For the CI22 and CI24M/R implants (the implants used to do the research described in this document) the current law is:
and the inverse:
 
a step of 1 CL therefore equals a 2.05% increase of current, which translates into 0.176 dB.
 
For the Nucleus Freedom implant the current law has been changed to give make finer tuning possible. It becomes:
Which translates into a 1.82% increase (or 0.157 dB) increase in current per CL step.
Figure A4 shows the CL vs Current relation graphically.
 

Current level vs Current (left) and dB Current (right) for the CI22/CI24M/R implant (heavy line) and the CI24RE (Freedom) implant (thin line).

Current level vs Current (left) and dB Current (right) for the CI22/CI24M/R implant (heavy line) and the CI24RE (Freedom) implant (thin line).