The formant tracker PRAAT showed systematic errors with male speakers, while SNACK and ASSP performed better on male than on female speakers.
this interpolation facilitates an evaluation of formant tracker output independently of the voiced-unvoiced detection of the tracker algorithm (because for every time frame of the recording there exists a reference value); on the other hand the resulting quality measure might be compromised: if a tracker is 'conservative' in the sense that it produces output only for the parts of the input signal where it is quite confident (clearly voiced parts), then this tracker will outperform other trackers who produce results in parts of the signal where the tracking is compromised for instance by creaky voice or noise associated with consonantal constrictions etc.