The present invention relates to a microphone apparatus (10) with a main beamformer (F, BF) that provides a directional audio output (SF) by combining microphone signals (X, Y) from multiple microphones (11, 12).The quality of beamformed microphone signals normally depends on the individual microphones having equal sensitivity characteristics across the used frequency range. The invention enables automatic adaptation of the main beamformer (F, BF) to variations in microphone sensitivity and to changes in the alignment of the microphone apparatus (10) with respect to the user's mouth (7).This is achieved by having the microphone apparatus (10): estimate a suppression filter (Z) for an optimum voice-suppression beamformer (Z, BZ) based on the microphone signals (X, Y); estimate a candidate filter (W) for a candidate beamformer (W, BW) as the complex conjugate of the suppression filter (Z); estimate the performance of the candidate beamformer (W, BW); and replace a main filter (F) in the main beamformer (F, BF) with the candidate filter (W) if the candidate beamformer (W, BW) is estimated to perform better than the current main beamformer (F, BF).The invention may be used to enhance speech quality and intelligibility in headsets 1 and other audio devices that pick up user voice.