Sound & Pitch: To PointProcess (peaks)...


A command to create a PointProcess from the selected Sound and Pitch objects.
Purpose
to interpret an acoustic periodicity contour as the frequency of an underlying point process (such as the sequence of glottal closures in vocalfold vibration).
Algorithm
The voiced intervals are determined on the basis of the voiced/unvoiced decisions in the Pitch object. For every voiced interval, a number of points (or glottal pulses) is found as follows:

1. The first point t_{1} is the absolute extremum (or the maximum, or the minimum, depending on your Include maxima and Include minima settings) of the amplitude of the Sound, between t_{mid} – T_{0} / 2 and t_{mid} + T_{0} / 2, where t_{mid} is the midpoint of the interval, and T_{0} is the period at t_{mid}, as can be interpolated from the Pitch contour.

2. From this point, we recursively search for points t_{i} to the left until we reach the left edge of the interval. These points are the absolute extrema (or the maxima, or the minima) between the times t_{i–1} – 1.2 T_{0}(t_{i–1}) and t_{i–1} – 0.8 T_{0}(t_{i–1}).

3. The same is done to the right of t_{1}.
The periods that are found in this way are much more variable than those found by Sound & Pitch: To PointProcess (cc), and therefore less useful for analysis and subsequent overlapadd synthesis.
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© ppgb, July 22, 2007