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 vocal-fold 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 t1 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 tmidT0 / 2 and tmid + T0 / 2, where tmid is the midpoint of the interval, and T0 is the period at tmid, as can be interpolated from the Pitch contour.
2. From this point, we recursively search for points ti 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 ti–1 – 1.2 T0(ti–1) and ti–1 – 0.8 T0(ti–1).
3. The same is done to the right of t1.

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 overlap-add synthesis.

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© ppgb, July 22, 2007