Determining the formants of a vowel

A vowel's formants are the frequencies at which it resonates; that is, the frequencies which are particularly loud in an acoustic signal. Each vowel has its own set of signature formants. Vowels in different dialects also have different formant patterns. This tutorial is intended to show you how to determine vowel formants in your own speech.

Extracting formants is no simple task. It involves recording your sample and creating a spectrogram. Fortunately, there is software that allows a user to do all of these. The Language Samples Project uses Praat, a shareware product created by the linguist Paul Boersma. When using Praat, there is an intermediate step, which is to convert the recorded sample into a Praat object.

  1. Recording your sample

    1. To analyze your speech, Praat first needs to have a sound file to work with. Choose the "Record Sound..." option under the "New" menu. This calls up the SoundRecorder window.

      • Make sure the Sample rate is set at 44100. The Input Source may be either External Mic (recommended) or Sound In. You will know that the program can detect your speech because the Meter will react to any sound picked up by your microphone, even if it is not recording. If you do not see colours spiking in the Meter, double check to make sure your microphone is plugged in.

    2. To obtain your sample, click the Record button and speak into the microphone. When you have finished, click Stop. You may listen to the recording again by clicking Play.

      • You may need to try more than once to get a good sample. Holding the microphone too close to your mouth will result in the signal having loud puffs and hisses. If this happens, try holding the microphone a few inches farther away.

    3. If you are satisfied with your sample, you can now save it as a .WAV file. Do not click the Close button! Instead, open the "File" menu in the SoundRecorder window, and choose "Write left channel to WAV file." This will let you save your recording as a digital file. Give your sample a name and remember which folder you're saving it in. Once the file has been saved, you may close the SoundRecorder window.

      • Prevent future hassles by choosing an easily identifiable name. For example, if your name is Norma and the word you recorded is "thing", name the file "NormaThing.wav" instead of just "sample.wav", "Norma.wav", or "thing.wav". Otherwise, if Norma and Nicole both had files named simply "sample.wav" or "thing.wav", either one of them might be analyzing the wrong sample at a later date!

    4. If you prefer, you may record your sample with any other recording software. Praat can import samples in a number of formats, including .WAV and .AIFF.

  2. Making an object

    1. Praat is designed to create different "objects" from sound files, and it can only work with these objects. Objects are normally listed in the Praat Objects window. The first object you need to add is the sound file itself. To do so, open the "Read" menu and choose "Read from file...". This will allow you to open your .WAV file as an object. Choose your sound file as you would choose any other document, by finding the proper folder and locating the file. When you click Open, Praat will add the file as a 'Sound' object.

      • You can rename and edit (clip, trim) this object without affecting the original .WAV file. So if you mess up, don't worry! You can higllight an unwanted Sound object and click Remove at the bottom of the window. Then read the .WAV file over again as a new object.

    2. Your Sound object is now something that Praat can apply various functions to, creating more objects in the process. Some of these other objects include spectrograms. You can examine each object in a separate window, but the commands for doing so differ, diepending on the nature of the object.

  3. Viewing a spectrogram

    1. There are two ways of getting spectrograms in Praat. One way is to examine your Sound object itself, by clicking the Edit button in the Praat Objects window.

      • If you don't see an Edit button, make sure your Sound object is highlighted.

    2. The Edit button opens another window, named for the Sound object. You should see a waveform in this window, as well as several drop-down menus.. To see the spectrogram, open the "Spectrogram" menu and choose "Show". The window should now be a split screen, with a waveform on top and a spectrogram on the bottom. The spectrogram is a graph that plots frequency ( y-axis) and amplitude (darkness) over time (x-axis).

      • Make sure you choose "Spectrogram > Show" and not "Spectrogram > View".
        To have a better view of the spectrogram, delete the empty space that is probably found before and after your sample. Highlight those areas and choose "Edit > Cut".

    3. You should now be able to see formants in the window, as dark, mainly horizontal bands. The horizontal cursor in this window can give you an idea of the frequencies of these formants. If you click anywhere on the spectrogram, you will see a time value at the bottom and a frequency value at the left. You should also see the intersection of a vertical and horizontal red line at the point on which you clicked. So if you click in the vertical centre of a formant, you can determine its frequency very easily.

    4. Another way to view a spectrogram is to create a Spectrogram object. Instead of pursuing Step (3a), you would have your Sound object highlighted in the Praat Objects window. Click on the Spectrum - button and choose "to Spectrogram...".

    5. You will see a window appear that gives you several options about the specifications of the spectrogram. Clicking the Defaults button will give you decent settings, but you may want to try reducing the Maximum Frequency to anywhere between 5000 and 7000 Hz. This will reduce the amount of empty space on the ensuing spectrogram, but it will also widen the formants, making it harder to determine their center with precision. Once you have settled on your settings, click OK.

      • Increasing the Analysis Width to 0.05 s will create a wide-band spectorgram.

    6. You will see a new object in the Praat Objects window, called Spectrogram [name]. When this object is highlighted, click the View button to see the spectrogram. A window will appear with the Spectrogram plotted againts time and frequency, just like in Step (3b). However, this spectrogram will not give you precise frequency values; you would need to estimate a frequency using the scale on the y-axis. So while this way of obtaining a spectrogram gives you the option of viewing it to your specifications, it is harder to get a precise formant value.

Phonetics

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