The object is to improve the action of a directional microphone in real acoustic environments. To do this, it is envisaged that the interference powers in a directional microphone with three microphones are reduced in that a first and a second microphone signal are adaptively filtered with respect to a first direction, with a direction-determining first parameter being adapted in such a way that the summation of interference powers is reduced. The second and a third microphone signal is adaptively filtered with respect to the first direction, with a direction-determining second parameter being adapted in such a way that the summation of interference powers is reduced. The two parameters are different from each other. This makes it possible, even in real environments, to suppress two interference sources from different directions with one second-order directional microphone.