By distinguishing specific characteristics of incoming noise, the hearing instrument determines whether an omnidirectional microphone or a directional microphone should be used. For example, if the hearing instrument user is in a quiet environment, the omnidirectional microphone is selected to make as many sounds in the environment audible as possible. In contrast, if background noise is present, the directional microphone is used instead of the omnidirectional microphone. Noise from behind or on the side of the user is attenuated, so the user can better understand the speaker in front of him/her. Instead of fast switching, the "soft-fading" between microphones makes certain for the optimum in hearing comfort.

Directional microphones are an effective aid, especially when background noise is present. Unfortunately, they are very sensitive to wind. Wind causes additional noise directly in the hearing instrument and can also impair speech intelligibility. The modern Siemens hearing instruments detect this situation and fade from the directional microphone over to the omnidirectional microphone, noticeably reducing wind noise.