A cochlear implant is installed in a user's head 18 and comprises an electrode array 20 which is situated on a user's basilar membrane inside the cochlea. The active electrodes are selected by controller 14 according to both an analysis of the frequency spectrum of the sound to be simulated (fig 5) and the amplitude waveform of the sound. The sound is received by microphone 10 and wirelessly routed to signal processor 12. The activation patterns of the electrodes may be a superposition of the amplitude pattern and a frequency spectrum patterns. Alternatively the two patterns may applied to the electrodes alternatively. The patterns are preferably applied at a rate higher that 8 kHz. The selection pattern of active electrodes on the array may also have its magnitude altered based on whether the simulated sound is in a period of compression of rarefaction.
