Tutorial for self study:

basics of phonetics and how to use Praat

In this tutorial you will get aquainted with the basic elements of acoustics and phonetic research. It is divided into 5 modules: basics of acoustics 1 and 2, spectrograms, LPC and PSOLA, which are, in turn, split up into different paragraphs (see index below). Every module is made of theoretical parts and of excercises (with answers in separate documents). It is useful to go through the excercises, as welll, in order to check your understanding, and because the answers are sometimes complementary to the explanations. Every module is also made up of a practical part, where you will learn how to work with Praat. Praat  is an open-source program for the analysis of speech, developed by Paul Boersma and David Weenink (Universiteit van Amsterdam).

In order to get Praat on your computer, go to http://www.fon.hum.uva.nl/praat > Download praat (choose the version for your operative system). It will take a second to download the program, either by downloading the self extracting executable file and double clicking on it or by downloading the ZIP file (and double clicking on it). In both ways, a Praat or Praat.exe file will appear, which is the Praat program itself. It is handy to make a shortcut link of Praat to an easily accessible location on your computer, for instance on the desktop (in Windows, click on praat.exe with the right mouse botton > Send to > Desktop, or click on right click on the desktop > New > Shortcut > Browse to find the Praat file). There is also a Praat user list (http://uk.groups.yahoo.com/group/praat-users/), where people share their knowledge posting questions and answers.

The audio files that we will be using are downloadable from
http://www.let.uu.nl/~Hugo.Quene/personal/onderwijs/sprekenenverstaan/practicum20070725.zip
or from
http://www.let.uu.nl/~audiufon/data/pracfon1.html

Acknowledgements

This tutorial was written by Clizia Welker (cliziaw at libero.it) and supervised by Hugo Quené http://www.let.uu.nl/~Hugo.Quene. It was funded by the ICT-centrum, Faculteit der Letteren, Universiteit Utrecht, in the frame of a 2006 project for students' self study.

Index of contents:


A. Basics of acoustics 1:

1. Sound and sound waves
1.1. What is a sound wave?
1.2. Acoustic media
1.3. Pressure
1.4. Questions and excercises A.1

2. Recording sound
2.1. Microphone
2.2. Analog recording
2.3. Digital recording
2.3.1. Binary number system: how does a computer handle with numbers?
2.3.2. Sampling rate
2.3.3. Quantization
2.3.4. DAT recording
2.3.4. Audio formats
2.4. Questions and excercises A.2
2.5. Recording sound on your computer

3. Oscillogram: a way of visualizing sound waves

4. Frequency
4.1. Questions and excercises A.3

5. Amplitude
5.1. Root mean square amplitude

6. Energy, power and intensity
6.1. Amplitude level and intensity level: decibel scales
6.2. Questions and excercises A.4

7. Phase
7.1. Questions and excercises A.5

8. Getting started with Praat
8.1. Oscillogram
8.1.1. Drawing an object in the picture window
8.3. Pitch
8.4. Intensity
8.5. Segmenting a waveform (cutting, pasting)
8.6. Labelling a waveform
8.7. Making a sine signal
8.8. Questions and excercises A.6 and A.7

New concepts introduced in this module

Sound wave
Pressure
Analog
Digital
Binary number system (bit, bytes)
Sampling frequency
Alias frequency
Antialiasing filter
Nyquist frequency
Quantization
Quantization noise
Digital Audio Tape
Audioformats, lossy, lossless
Oscillogram
Sine tone
Frequency (f)
Pitch
Fundamental frequency (F0)
Period (T)
Wave length λ
Amplitude (A)
Root mean square amplitude (RMS)
Logarithm
Intensity (I)
Amplitude level
Intensity level
Decibel (dB)
Phase (φ)
Voice onset time
Octave errors


How to work with Praat

Recording sound on your computer
Recording a speech object in Praat
Saving a sound file to your computer
Open a saved sound file with Praat
Displaying oscillograms
Drawing an object in the picture window
Pasting a diagram to a text editor
Saving a diagram as EPS file
Printing a diagram
Displaying the pitch contour
Getting information about pitch
Pitch settings
Adjusting octave errors

Editing a pitch object
Drawing the pitch contour in the picture window
Displaying the intensity contour
Getting  information about intensity
Intensity settings
Drawing the intensity contour in the picture window
Segmenting a waveform (cutting, pasting)
Labelling a waveform
Making a sine signal

B. Basics of acoustics 2:

1. Complex signals
1.1. Questions and excercises B.1


5. Using Praat
5.1. Making a white noise signal with Praat
5.2. Making a spectrum
5.3. Drawing a spectrum in the picture window
5.4. Filtering a signal
5.5. Questions and exercises B.6


New concepts introduced in this module


How to work with Praat

Making a white noise signal
Making a spectrum
Drawing a spectrum in the picture window
Filtering a signal

C. Spectrograms:

1. What is a spectrogram

2. Spectrograms in Praat
2.1. Making a spectrogram in Praat
2.2. Spectrogram parameters: how do they influence the spectrographic analysis and how to set them in Praat
2.2.1 Frequency range, Hz
2.2.2 Hz bandwidth (window length)
2.2.3 Background noise (dynamic range, dB)
2.2.4 Time step
2.2.5 Frequency step
2.2.6 Method (Fourier transformation)
2.2.7 Window shape
2.2.8 Praat parameters affecting the displayed energy

3. Formants in spectrograms
3.1.1. Tracking formants in Praat
3.1.2. Formant settings: how do they affect formant tracking and how to set them in Praat
3.1.2.1. Maximum formant
3.1.2.2. Number of formants
3.1.2.3. Window length
3.1.2.4. Dynamic range
3.1.2.5. Dot size
3.1.3. Getting formant information in Praat

4. Reading a spectrogram

5. Drawing a spectrogram in the picture window

6. Questions and excercises C.1

New concepts introduced in this module

How to work with Praat

Making spectrograms
Setting the spectrograms' parameters
Tracking formants
Setting formant parameters
Getting formant information
Reading the spectrogram
Drawing a spectrogram in the picture window
Garnishing the spectrogram

D. LPC:

1. What is LPC

2. LPC analysis
2.1. Number of coefficients and number of detected formants

3. LPC synthesis

4. Limits of LPC

5. LPC in Praat
5.1. Choosing the number of formants
5.2. Choosing the LPC location
5.3. Performing the LPC analysis on the signal
5.3.1. Setting the LPC analysis parameters
5.3.2. Getting formant information
5.3.3. Creating the LPC spectral slice
5.3.4. Controlling the LPC outcome by resynthesis
5.4. Drawing the LPC spectral slice in the picture window

6. Questions and exercises D.1

New concepts introduced in this module

LPC
Error or residue
Coefficients
Frame
Pulse

How to work with Praat

How many formants are to be present in the signal?
Getting information about the sampling frequency
Resampling the signal
Choosing the LPC slice location
Performing LPC analysis on the signal
Setting the LPC analysis parameters
Getting formant information
Creating the LPC spectral slice
Controlling the LPC outcome by resynthesis
Drawing the LPC spectral slice in the picture window

E. PSOLA:

1. What is PSOLA?

2. Manipulating pitch in Praat (through PSOLA)
2.1. Playing the manipulation object
2.2. Replacing the pitch contour

3. Manipulating duration in Praat (through PSOLA)
3.1. Replacing the duration tier

4. Questions and exercises E.1

New concepts introduced in this module

Psola
Pitch manipulation
Duration manipulation

How to work with Praat

Manipulate pitch (through PSOLA)
Manipulate duration (through PSOLA)
Modifying the duration of the whole utterance
Playing the manipulation object
Replacing the pitch contour
Replacing the duration tier
Storing the manipulated signal








References

 - Denes, P. B. and Pinson E. N. The speech chain. The physics and biology of spoken language. W.H. Freeman and Company, New York, 1993 (second edition)
- Janse, E. Production and perception of fast speech. Proefschrift, Universiteit Utrecht. LOT Dissertation series, 69 LOT, Utrecht 2003)
- Johnson, K. Acoustic and auditory phonetics. Blackwell Publisher Inc. Cambridge, Massachusetts, 1997
- Noteboom, S.G. and Cohen, A. Spreken en verstaan. Een nieuwe inleiding tot de experimentele fonetiek.Van Gorcum, Assen, 1983
- Reetz, H. Artikulatorische und akustische Phonetik. Wissenschaftlicher Verlag, Trier, 2003
Rietveld, A.C.M. and van Heuven, V.J. Algemene fonetiek. Coutinho, Bussum 2001 (second edition)
- Rossing, Thomas D. The Science of Sound. Th. Addison-Wesley, Northern Illinois University, 1990 (second edition)
- van Lieshout, P. Praat. Short tutorial (link for downloading on the Praat website) 
- Werkboek bij practicum spreken en verstaan: inleiding fonetiek (200300287), Hugo Quené
- http://www.fon.hum.uva.nl/praat/
- http://www.indiana.edu/~acoustic/spsites.html 
- http://www.indiana.edu/~emusic/etext/acoustics/chapter1_intro.shtml
- http://www.glenbrook.k12.il.us/GBSSCI/PHYS/Class/sound/u11l1b.html
- http://www.let.uu.nl/~Hugo.Quene/personal/faq/spraakprogr.html#
- http://person.sol.lu.se/SidneyWood/praate/frames.html


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