The minimum requirement for a beamforming algorithm is to have at least two mics. For the demonstration, ST implements the concept using digital microphones. The output of these mics is the Pulse Density Modulation (PDM). The advantage of this communication protocol is that it requires only two signals, clock and data output. PDM digital mics are not mandatory. Technically, it is also possible to implement the algorithm using analog mics. The library works when the mics are together against one another, or at a distance of up to 2.1 cm. A 45° angle of selectivity is achievable with a four mics array.