Do X in Y: Randomize duration and F0 of speech files in Praat

Randomize duration and F0 of speech files in Praat

Summary: I describe a script that makes random modifications to duration and pitch. It can serve as an example for how to read in all .wav files in a directory and modify them from the command line.

For a machine learning project, we wanted to induce variability in a set of speech files without recording more tokens of our critical words. We thought, “let’s just use a Praat script to randomly jigger duration and F0 — that can’t be hard, can it?” Well, it is harder than I thought given that I don’t really grok Praat scripting — it is the most foreign and strange programming language I’ve ever encountered.

After consulting with various colleagues, I remembered that Sergey Kornilov had used a script to compress lots of files for a project. He sent me his script. I found a script by Shigeto Kawahara of Keio U. in Japan that modified pitch. Putting them together, I now have a script that is called from the command line and reads in all .wav files in a directory (the directory where the script is located), randomly compresses/expands the file according to a hard-coded range (i.e., you have to change the values in the file), randomly adjusts pitch (by multiplying by a scalar), and writes the resulting file in a folder called output that must exist in the starting directory. The file names include tags indicating how duration and pitch were modified. Here’s the script. I hope someone else finds it helpful! You can copy the code and paste it into a text document that you might call something like vary_duration_and_pitch.praat.

— jim magnuson

# 2017.11.17, Jim Magnuson, based on a compression script by
# Sergey Kornilov and
a pitch modification script by
# Shigeto KAWAHARA of Keio U.

# (
# kludgy script to shift pitch by random factor between
# minF0 and maxF0
and compress/expand by random factor between
# minComp and maxComp. 

# It does this for every .wav file in the directory where the
script is located, and writesresulting files in ./output
# (so you must create a folder called output; note

# that the script will overwrite files in that directory
# without warning!).

# The output files have _dur_X and _f0_Y inserted in their
# names. For example,
_dur_87 means compression to factor of
# 0.87, _dur_108 means compression
(expansion) to factor of
# 1.08, etc.

# set locations
inputDir$ = "./"
outputDir$ = "./output/"

# set ranges for pitch and compression
minF0 = 0.5
maxF0 = 2.0
minComp = 0.5
maxComp = 2.0

# used to incorporate duration and F0 changes
# in out file name

resolution = 100

# read *.wav filenames into strings
strings = Create Strings as file list: "list", inputDir$ + "/*.wav"
numberOfFiles = Get number of strings

# now loop through .wav list
for ifile to numberOfFiles
       # open file in position ifile in string list
       filename$ = Get string... ifile

       # give a little info on the console re: progress
       appendInfoLine: "Working on " + inputDir$ + filename$

       # read the actual file
       Read from file: inputDir$ + filename$

       # set random duration factor
       duration_scalar = randomUniform(minComp, maxComp)

       # 75 and 600 are standard parameters for the
# frequency range (hz)
used in periodicity analysis;
# the last argument is the compression factor

       Lengthen (PSOLA)... 75 600 duration_scalar

       # this is going to require Manipulation commands,
# so we need to
select the sound; let's name it
       this_sound$ = selected$ ("Sound")

       # grab it + give params for onset of analysis window and
       # frequency range used for periodicty analysis
       To Manipulation... 0.01 75 600      

       # pop pitch tier into memory (apparently)
       Extract pitch tier

       # set random pitch change factor
       pitch_scalar = randomUniform(minF0, maxF0)

       # modify pitch of the pitch tier in memory
       Formula... self * pitch_scalar;

       # reselect the sound and replace pitch tier
       select Manipulation 'this_sound$'
       plus PitchTier 'this_sound$'
       Replace pitch tier

       # reselect the sound??? and resythesize
       select Manipulation 'this_sound$'
       Get resynthesis (PSOLA)

       # create rounded versions of the pitch and
# duration factors for use in filename

       pitch_scalar_rounded = round(pitch_scalar * resolution)
       duration_scalar_rounded = round(duration_scalar * resolution)
       filenameDur$ = " 'filename$'" - ".wav" + "_dur" + "_" + string$(duration_scalar_rounded) + "_f0" + "_" + string$(pitch_scalar_rounded) + ".wav"

       # update user
       appendInfoLine: "         writing to " + outputDir$ + filenameDur$

       Write to WAV file: outputDir$ + filenameDur$
       select Strings list


select all

# end of script