Detection of rotational speeds of sound sources based on array measurements

Rotating machinery such as fans feature a variety of sound generating mechanisms. In addition to stationary sound sources and sources moving synchronously to the measured object, sources rotating at different speeds can occur. This paper presents a method for detecting different rotational speeds of multiple dominant sources present in one data set. It is based on modal decomposition and processing of data measured with a circular microphone array. The method is applied to data sets with simulated point sources as well as measurement data of an axial fan with forward-skewed blades at two different operating points.