Figure 3.
Details of pitch period entropy (PPE) calculation: (a-b) pitch period p(t) in semitones relative to note C3 on the musical scale, (c-d) residual of pitch period r(t) after spectral whitening filter, (e-f) probability densities P(r) of residual pitch period r. PPE value is the entropy of this probability density). Left panels are for a healthy subject, right panel is for a person with Parkinson's.