Let us consider the hypothetical case of a microphone arraycomposed of microphones, as seen in figure ,with identical frequency response and equal distance between anytwo adjacent microphones, of value d meters. If only thehorizontal directivity pattern is considered ()and have microphones with equal amplitude weights , the main lobe can be steered to the direction ' usinga basic delay-and-sum beamforming by applying the following phaseweights to the channels:
Microphone arrays consist of multiple microphones functioning as a single directional input device: essentially, an acoustic antenna. Using sound propagation principles, the principal sound sources in an environment can be spatially located and distinguished from each other. Distinguishing sounds based on the spatial location of their source is achieved by filtering and combining the individual microphone signals. The location of the principal sounds sources may be determined dynamically by analysing peaks in the correlation function between different microphone channels.
Microphone arrays based on the minimum variance distortionless response (MVDR) beamformer are among the most popular for speech enhancement applications. The original MVDR is excessively sensitive to source location and microphone gains. Previous research has made MVDR practical by successfully increasing the robustness of MVDR to source location, and MVDR-based microphone arrays are already commercially available. Nevertheless, MVDR performance is still weak in cases where microphone gain variations are too large e.g., for circular arrays of directional microphones. In this paper we propose an improved MVDR beamformer which takes into account the effect of sensors (e.g. microphones) with arbitrary, potentially directional responses. Specifically, we form estimates of the relative magnitude responses of the sensors based on the data received at the array and include those in the original formulation of the MVDR beamforming problem. Experimental results on real-world audio data show an average 2.4 dB improvement over conventional MVDR beamforming, which does not account for the magnitude responses of the sensors.
In Windows Vista and later, support is provided for microphone arrays. In most situations, a single microphone embedded in a laptop or monitor does not capture sound very well. An array of microphones performs better to isolate a sound source and reject ambient noise and reverberation. The property specifies the geometry of a microphone array. The property value, , describes the array type (linear, planar, and so on), the number of microphones in the array and other features.