Noise-reducing directional microphone array

摘要

In one embodiment, a directional microphone array having (at least) two microphones generates forward and backward cardioid signals from two (e.g., omnidirectional) microphone signals. An adaptation factor is applied to the backward cardioid signal, and the resulting adjusted backward cardioid signal is subtracted from the forward cardioid signal to generate a (first-order) output audio signal corresponding to a beampattern having no nulls for negative values of the adaptation factor. After low-pass filtering, spatial noise suppression can be applied to the output audio signal. Microphone arrays having one (or more) additional microphones can be designed to generate second-(or higher-) order output audio signals.

主权项

1. A method for processing audio signals, comprising:
(a) generating first and second cardioid signals from first and second microphone signals; (b) determining whether any of wind noise, thermal noise, and circuit noise are present in the first and second microphone signals; (c) generating a first adaptation factor, wherein: the first adaptation factor is constrained to a first range of values if the determination of step (b) is that wind noise, thermal noise, and circuit noise are not present in the first and second microphone signals; and the first adaptation factor is constrained to a second range of values, different from the first range of values, if the determination of step (b) is that at least one of wind noise, thermal noise, and circuit noise is present in the first and second microphone signals; (d) applying the first adaptation factor to adjust amplitude of the second cardioid signal to generate an adapted second cardioid signal; and (e) combining the first cardioid signal and the adapted second cardioid signal to generate a first output audio signal, wherein, when the first adaptation factor is constrained to the second range of values, the first output audio signal corresponds to a first beampattern having no nulls.