A new approach to acoustic beamforming from virtual microphones based on ambisonics for adaptive noise cancelling

Interference in three-dimensional audio systems is a problematic issue. Eliminating noise, or any other disturbing source, without affecting the spatial audio rendering, is challenging, indeed. Using the least possible number of microphone capsules and reduced size is another issue. An elementary way for accomplishing this job makes use of a 3D audio technique called Ambisonics and a coincident microphone array of 4 elements. This technique allows shaping cardioid-like virtual microphones pointing to a jamming source. This disturbing signal can be used to feed an adaptive noise canceller and kill noise from the 3D recording. Evidently, a 4-capsule array extracts cardioids up to first order. The final result can be improved if microphones with higher directivity are employed. This paper presents a method for deriving highly-directive virtual microphones by means of a 4-capsule ambisonic array and spaced virtual capsules.