1. A method of monitoring the condition of a machine, said method comprising: receiving an input complex signal from the machine wherein the input complex signal comprises a plurality of signal components, the plurality of signal components comprising at least one signal component containing a pre-determined frequency of interest and at least one signal component containing noise; processing the input complex signal and generating an output complex signal comprising a plurality of signal components, the plurality of signal components comprising at least one signal component containing a pre-determined frequency of interest and at least one signal component containing noise, wherein said processing the input complex signal comprises executing a fixed-step integration; and processing the output complex signal to assess whether a fault exists.