signal processing which would be needed for a full adaptation to different acoustic environments these features can be accomplished at least in part by means of the following behaviour a in a constantly strongly changing situation the partly significant changes in signal processing which would be needed for a full adaptation to different sound classes shall be averaged out in order to achieve a more constant more stable signal processing b when after strong changes an acoustic situation is again practically stable for a certain span of time the signal processing shall slowly fade towards the appropriate parameter set values activity parameter sets for this situation c only when class similarity factors have remained relatively stable for a sufficiently long time i e detection of a rather constant acoustic situation for a certain span of time the hearing device shall again react fast upon a detected significant change in the acoustic environment fig3 is a schematic illustration of an activity parameter a 1 and a corresponding time averaged activity parameter a 1 as a function of time t which shall illustrate the above depicted behaviour wherein u2014 for reasons of simplicity u2014 only one parameter of an activity parameter set or an activity parameter set comprising only one parameter is assumed when fast great changes happen to a 1 a 1 will not fully follow a 1 later then when changes in a 1 become weaker a 1 slowly drifts towards a 1 finally after quite a while of approximately constant conditions a rapid strong change in a 1 will be followed by a 1 rather quickly and in full.