The phase differences of microphones of a hearing aid microphone are to be reduced. To do this, the level of an output signal (y1(t)) of a directional microphone is compared with an omnidirectional signal (y1'(t)). If the level of the output signal of the differential directional microphone (y1(t)) is above the level of the omnidirectional signal (y1'(t)), this level difference is minimized by an adaptive, frequency-selective transit time compensation (A) in individual frequency bands and phase matching of the microphones (M1,M2) is thus achieved. By means of an alternative method, microphone matching is achieved in that the measurable delay of the two microphone signals (x1,x2) is adaptively limited in individual frequency bands to a maximum value corresponding to the sound transit time between the microphones (M1,M2). Phase matching without knowing the position of a sound source can thus be achieved.