Left: experimental apparentus showing a microphone array in the “measurement plane” used to sense the acoustical field radiated by a rotating machine in a testbench. Right: spatial distribution of a cyclostationary indicator mapped to the “identification plane” and targetted to two types of bearing fault – outer (IRF) and inner (ORF) race faults in left and right columns, respectively – tested in healthy (first raw) and faulty cases (outer and inner race faults in second and third raws). Red spots indicate location of the faults though high values of the cyclostationary indicator [106].