An implantable device having a multi-channel electrode array, each output channel being associated with an electrode in the array, the device comprising: an audio processing stage for processing an input audio signal to produce a plurality of output channel signals each representing an associated band of audio frequencies; a timing and envelope detector for processing the output channel signals in a sequence of sampling intervals, wherein for each sampling interval, the processing includes determining for each output channel signal: i. a set of requested pulse timings containing a plurality of pulse timing requests, and ii. a set of corresponding envelope signals representing pulse magnitude for pulse timing requests; a pulse selection amplitude definition stage for determining for each set of requested pulse timings: i. a set of output pulses at specified times selected from the set of requested pulse timings based on the envelopes of the requested pulses and on a pulse selection inhibition function, and ii. a stimulation amplitude associated with each output pulse; and the multi-channel electrode array for applying the output pulses at their associated stimulation amplitudes to surrounding tissue; characterised in that the inhibition function is constant during an absolute inhibition phase and then decreases towards zero over another period which defines a relative inhibition phase. an audio processing stage for processing an input audio signal to produce a plurality of output channel signals each representing an associated band of audio frequencies; a timing and envelope detector for processing the output channel signals in a sequence of sampling intervals, wherein for each sampling interval, the processing includes determining for each output channel signal: i. a set of requested pulse timings containing a plurality of pulse timing requests, and ii. a set of corresponding envelope signals representing pulse magnitude for pulse timing requests; i. a set of requested pulse timings containing a plurality of pulse timing requests, and ii. a set of corresponding envelope signals representing pulse magnitude for pulse timing requests; a pulse selection amplitude definition stage for determining for each set of requested pulse timings: i. a set of output pulses at specified times selected from the set of requested pulse timings based on the envelopes of the requested pulses and on a pulse selection inhibition function, and ii. a stimulation amplitude associated with each output pulse; and the multi-channel electrode array for applying the output pulses at their associated stimulation amplitudes to surrounding tissue; i. a set of output pulses at specified times selected from the set of requested pulse timings based on the envelopes of the requested pulses and on a pulse selection inhibition function, and ii. a stimulation amplitude associated with each output pulse; and the multi-channel electrode array for applying the output pulses at their associated stimulation amplitudes to surrounding tissue; characterised in that the inhibition function is constant during an absolute inhibition phase and then decreases towards zero over another period which defines a relative inhibition phase.