Abstract: In accordance with one aspect of the present invention, a method for detecting a change in the performance of an audio signal processing path is disclosed. The method comprises: selecting a characteristic of a received audio signal indicative of its energy content; determining first and second predetermined values of the selected energy characteristic at respective first and second audio signal frequency bands; calculating a ratio of the first and second predetermined values for a reference time period and a test time period; and comparing the ratio at the reference time period with the ratio of the test time period to determine a performance change in the audio path.

Abstract: A totally implantable cochlear implant system forming a single implantable unit (40). The unit (40) has an implantable power source (43) that provides the power requirements of the implantable unit (40). The unit (40) also has an on-board microphone (42) that detects external sounds, such as speech, and outputs acoustic signals representative of the detected sounds. The unit further includes speech processor circuitry (44) that directly receives the acoustic signals from the microphone (42) and converts the signals into stimulation signals representative of the detected sounds. An electrode array (20) suitable for insertion of the cochlea (2) of an implantee receives the stimulation signals and transmits electrical stimulations to the implantee'auditory nerve (9).