Chapter 5 Charting Vowels

Charting Vowels 母音圖表

Formats One and Two 第一及第二共振峰

The vowels of a particular speaker can be described precisely by stating their formant frequencies. People with larger resonating cavities will produce formats with comparatively low frequencies, and others will have higher formant frequencies because they have smaller vocal folds.

The most useful representation of the vowels of a language is a plot showing the average values of format one and format two for each vowel as spoken by a group of speakers.




See the figures below. The first formant has a low pitch for i (heed), a high pitch for a (hod), and a low pitch for u (who’d) which is the opposite of what the tongue does (high in heed, low in hod, and high in who’d)


The second formant is hign for i (heed) and low for u (who’d). The tongue is in front of the mouth for i (heed) and towards the back for u (who’d), but the vowel in which the tongue is furthest back in the mouth is a (hod). It is apparent that the frequency of the second formant is related to something else as well as tongue position. The major part of the lowering of the second formant is due to the increase in lip rounding.






In the figure below, the bars for each vowel have been replaced by points. This kind of representation of vowels is known as a formant chart.



Comparing English Vowels 英語母音的比較

In the figure below, the vowels in bay and bow are indicated by lines, to show that these vowels are diphthongs, starting with one vowel quality and ending with another.


One thing to note about the charts above is the difference between two different genders, women and men. The men’s vowels have lower formant frequencies, resulting in their chart being more compressed, This is because men have larger vocal tracts, containing bigger bodies of air. These larger bodies of air vibrate more slowly, so that the formats have lower frequencies.




The major difference between General American English and BBC English is the large change in quality that occurs in the diphthong in the words such as  no, dough, and bow.


In the figure below, the vowel in bird has the same quality as the first vowel in about or the last vowel in sofa, and like them has no r-coloring. As a result of the vowel in bird occupying the space in the center, the BBC English vowel in bud is pushed down so that is somewhat lower on the chart, with a higher first formant frequency that its General American counterpart.



Formant Three 第三共振峰

Formant three has very little function in distinguishing the vowels. For all English vowels, the third formant frequency can be predicted fairly accurately from the frequencies of the first two formants, except the vowel in most forms of American English bird. The vowel r has a very low third formant frequency. Its first and second formants are often very similar to those in hood, but it has a very different quality.

The frequency of the third formant is very much affected by the position of the lips. This makes it important in some languages. It so happens that neither General American English or BBC English have vowels with the same tongue positions but different lip positions.




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