Hi xwbcf,

I have a little more experience to share after reading your comments, and just initiate another thread to invite additional viewpoints.

Your comment:
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回答: NCE (III) Lesson 37: The Westhaven Express (followup reading) 由 billnet 于 2009-05-16 21:33:08
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个人感觉要注意的一个词是black, 嘴好像张得不够大
BTW，大a和小e,我一直有这个问题
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Reply:
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Quite agree and I should open mouth larger when saying that sound.

Speaking of this Front vowel in the word /black/, to my surprise/observation that the native people here don\'t say this sound via opening their mouth as large as what we (at least I) imagined, and we didn\'t see that they have obvious change in the mouth when pronoucing this sound. ( I am surprised when hearing their saying sing, sang, sung without opening their mouth as large as we do to pronounce the sang sound). However, they distinct the Front vowels very clearly. The point is that (based on me) they habitually pronunce the front vowels proportionally with regards to the height of the tongue and forward/backward of the tongue. For us, we need to examine ourselves if we allocate proportionally to the Front Vowels with regards to the positioning of the tongue and height of the mouth opening when pronoucing them.
To test our mastery of those sounds, we need to compare them by grouping the words together,like, black->beg->bit->beat, and we can see that we have a distinction of them, and keep this habit permanently.

Below is a comparison of the Front Vowels based on Tongue position and Height of mouth opening. As some symbols are not displayed, just used a word to represent that sound.

Vowel sound in /black/, /sang/, /sat/:
- The tongue is positioned slightly forward and low in the oral cavity, with the tip positioned behind the lower teeth.
- The mandible (lower jaw) is lowered more than for any other front vowel.
- The lips are unrounded but may be retracted.

Vowel sound in /bet/, /egg/:
- The tongue is positioned forward and high in the oral cavity with the sides in contact with the teeth laterally and the tip positioned behind the lower teeth.
- The mandible is elevated.
- The lips are unrounded, and maybe retracted.

Vowel sounds: /ei/ and /i:/
- The tongue is positioned forward and high in the oral cavity with the sides in contact with the teeth laterally and the tip positioned behind the lower teeth.
- The mandible is elevated.
- The lips are unrounded, and maybe retracted.

/I/ word like /Invite/ /pin/
- The tongue is positioned forward and slightly lower in the oral cavity than for /i:/, with the sides in contact with the teeth laterally and the tip positioned behind the lower teeth.
- The mandible is slightly lower than for /i:/.
- The lips are unrounded.

/a/ word lik /path/
- Although variable, the tongue is slightly back from and low in the oral cavity, with the tip positioned behind the lower teeth.
- The mandible is slightly lowered, although its position varies depending on phonetic context.
- The lips are unrounded