In a hearing aid having a microphone system composed of multiple microphone units, in order to avoid artefacts from being created when switching between different directional characteristics, the signal levels of microphone signals that respectively originate from different microphone units with different-order directional characteristics are matched with regard to a reference signal. The switching or superimposition is then always carried out between microphone signals with the same signal level, so that the switching or superimposition does not result in any sudden level changes.