1. In a patient monitor configured to obtain signals responsive to physiological parameters of a monitored patient, a method for filtering one or more of said signals to improve a determination of a pulse rate of the monitored patient, the method comprising: receiving one or more signals indicative of light attenuated by body tissue of pulsing blood in said monitored patient, said one or more signals usable to determine physiological measurements and a pulse rate of said monitored patient; electronically determining an initial frequency estimate of said pulse rate; electronically combining at least one sinusoidal waveform responsive to said estimate of said pulse rate with said one or more of said signals to produce a predetermined signal response; and electronically signal component processing the combined signal to determine an output measurement of said pulse rate.