The TetraMic is a soundfield system that utilizes a patented four-capsule microphone and decoding software. On the top of the tiny mic are four sub-cardioid electret-condenser capsules of 12 mm diameter mounted 90 degrees apart. The capsule grilles define the faces of a tetrahedron. Below the capsules is a slim brass handle with a built-in 6-pin tiny XLR connector. Other cables and connectors let you connect the mic to a recorder of your choice.
Listen to ambisonic audio samples here.