US Patent 8718290 Adaptive noise reduction using level cues

An audio device having two pairs of microphones for noise suppression. Primary and secondary microphones of the three microphones may be positioned closely spaced to each other to provide acoustic signals used to achieve noise cancellation/suppression. A tertiary microphone may be spaced with respect to either the primary microphone or the secondary microphone in a spread-microphone configuration for deriving level cues from audio signals provided by the tertiary and the primary or secondary microphone. Signals from two microphones may be used rather than three microphones. The level cues are expressed via an inter-microphone level difference (ILD) used to determine one or more cluster tracking control signal(s). The ILD based cluster tracking signals are used to control adaptation of null-processing noise suppression modules. A noise cancelled primary acoustic signal and ILD based cluster tracking control signals are used during post filtering to adaptively generate a mask to be applied against a speech estimate signal.