NOISE-REDUCING DIRECTIONAL MICROPHONE ARRAY

In one embodiment, a directional microphone array having (at least) two microphones mounted on opposite sides of a device generates forward and backward base signals from two (e.g., omnidirectional) microphone signals using diffraction filters and equalization filters. Each diffraction filter implements a (possibly different) transfer function representing the response of an audio signal traveling from a corresponding microphone around the device to the other microphone. A scale factor is applied to, for example, the backward base signal, and the resulting scaled backward base signal is combined with (e.g., subtracted from) the forward base signal to generate a first-order differential audio signal. After low-pass filtering, spatial noise suppression can be applied to the first-order differential audio signal. Microphone arrays having one (or more) additional microphones can be designed to generate second- (or higher-) order differential audio signals.