This paper reports on the rehabilitation following implantation of the French cochlear implant, Chorimac 12, in a 66-year-old woman. The electrical stimulation of the device should normally stimulate on a 400-6000 Hz bandwidth. However, tests that had been run after the four-month rehabilitation period indicate that there is no stimulation under 1000 Hz, 2000 Hz seems to be the best bandwidth for stimulation, and over 4000 Hz, almost nothing is audible. An "analytico-global" rehabilitation process has yielded results on vowel, consonant and sentence discrimination: pairs of vowels which offer major contrasts are best discriminated; fricatives are easier to recognize than stops; the longer a sentence is, the easier the patients can identify key words that facilitate identification; also, the more sentences carry phonetic differences, the easier it is to identify them. The results from the analysis of the phonetic material used during the rehabilitation, the new hearing impressions described by the patient and the acoustical measures from acoustic researchers allow us to quantify the restored hearing, define the acquired phonetic code and describe the level of performance reached by the patient.