The article introduces a novel approach for noise reduction based on distance
approximation of signal sources. This is achieved by estimation
of the specific acoustic impedance of the incoming signal. The method uses small-sized
two-microphone arrangements or so called twochannel
microphones which barely exceed the spatial extend of a single microphone.
The novel adaptive block-online algorithm significantly reduces the level of distant signals having the same angle of arrival as the closer source signal. The overall method has been tested in an anechoic chamber and a more realistic room with 250 ms reverberation time. The sources are located at distances of 5 cm and 1 m from the test microphone. The experiment shows a level reduction of 5.1 dB with regard to a distant noise source. The signal level of the close-tomicrophone speaker is not effected.
The approach is targeting on new applications but also provides algorithmic improvements for existing applications - e.g. for the noise reduction in hand-held microphones or for distance-dependent noise gates.
Index Terms: Active noise reduction, adaptive filters, spatial filters
Bibliographic reference. Fehér, Thomas / Richter, Dietmar / Jokisch, Oliver / Hoffmann, Rüdiger (2012): "Distance-dependent noise reduction for two-channel microphones", In INTERSPEECH-2012, 138-141.