How to manipulate the pitch contour of an utterance using PSOLA implemented
in Praat (ver. 4.0.7)
Based on Professor Mary Beckman's
"The speech science of speech synthesis", a seminar offered in Summer 2002.
(All mistakes are mine, though)
1. Open a sound object: (menu)Read ==> Read from file...
2. With the sound object selected, create a manipulation object from it:
(button) To Manipulation...
If you want, you can adjust the time steps, minimum/maximum
pitch, but the default values are fine for most cases
3. With the manipulation object selected, open the manipulation window:
(button) Edit
4. From the manipulation window, you can see many green "manipulation dots"
separated from each other by 10 ms (set in 2)
Zoom in onto one of the vowel segment, and you will
see the actual dots (green dots turn to red when selected).
Select the vowel segment by left-click-dragging
over the vowel segment and zoom in onto it: (button) sel
The dots are pitch points that you can drag around to
modify the original pitch contour.
Since, however, the number of dots in a vowel segment
is too many, we need to "stylize" the pitch contour.
5. To stylize the pitch contour of a particular segment, you'd first need
to determine which points are perceptually important.
Let us assume, for example, the vowel that we're interested
falls gradually in its pitch contour.
Then we can set the beginning and end of the vowel
pitch point as determining the overall pattern of the actual pitch contour.
Once the anchoring pitch points are determined, we can
safely remove the other pitch points.
Select the other pitch points: Click-drag-release.
Remove the selected points: (menu) Pitch ==>
Remove pitch point(s)
Zoom out to see the whole utterance.
Play the (PSOLA) re-synthesized sound file to see if
the stylization process didn't lose any information that was present in the
original file.
6. Now you can drag the stylized pitch points around to manipulate the
pitch contour of the vowel.
First, you need to select the beginning pitch point
of the stylized section of the sound object: Click on the pitch point
(turning green to red)
Second, holding the pitch point with your left-mouse-button,
drag it around to set a new f0 value to that point.
Play the PSOLA-resynthesized object to listen to the
new pitch contour.
When you're satisfied with what you hear, you can create
as a sound object the PSOLA-resynthesized version of your stylized pitch
contour:
7. You can do this in the manipulation window: (menu) File ==>
Publish resynthesis.
Then you can locate this object in the object window
(below) and it's named "fromManipulationEditor".
NOTE: Unless you "write" it as a file, the object will
be destroyed when you exit Praat.
You can write the object as a .wav file: (menu) Write
==> Write to WAV file...
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