16. Waveforms, pitch track and WASP
In chapter three of Ladefoged you see a comparison between waveforms of the unvoiced aspirated and unvoiced unaspirated inital stops /t/ and /d/ realized as [t] and [tʰ]. A waveform is a graphic representation of the tiny air pressure variations produced by sounds, including the human voice.
can generate waveforms like the ones in the book yourself, with a remarkable
free program, WASP
('Waveforms, Annotations, Spectrograms & Pitch'), created
by Mark Huckvale of University College London. The latest version of WASP (the
last one in the list) can be downloaded in less than a minute from:
In addition to the software, you will also need a conference microphone to plug into your computer. Use the Windows volume control to adjust volume levels. Using earphones will help you hear the sounds clearly.
WASP has four main displays: waveform, wideband spectrogram, narrowband spectrogram, and pitch track (fundamental frequency estimation). You can also annotate, or label, your speech signals. Don't worry about the spectrograms just yet, though do try them out to see what they can do. We are most interested right now in waveforms. You can use these to see clearly, for example, differences between fully voiced, partially voiced and aspirated voiceless stops in English and other languages. Record some examples yourself, in all the languages you know; you can get someone to help for languages you are less familiar with.
'Pitch track' analyzes your speech signal to find the fundamental frequency, or the basic rate of vibration of your vocal folds at each sampled point in time, and then draws lines connecting the points. Of course you can only have a 'pitch track' where there is voicing, so you'll see breaks in the display where there are periods of silence or voicelessness. Or you may see a line suggesting you are producing a high pitch with your vocal cords, when really it's just high-frequency noise from sounds such as voiceless fricatives or the release of aspirated stops. Also, the pitch track is based on estimations and is not always completely accurate, so you should use it only as a reference. But the pitch track can provide feedback on your intonation, will trace Chinese tones, and can be a very useful tool for your work in phonetics and language learning.
WASP is great fun to play around on (and you should play with it; playing is the best way to learn!), but it is also a serious study and research tool. Consult the Help file for more information on how to use WASP.
Next: Three Tutorials on Voicing and Plosives
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