I attended Robin Barr's "Call 'Em As You 'Ear 'Em" Workshop

15 VOWELS OF ENGLISH (color-coded)

http://colorvowelchart.org/ graphic, as presented at Robin Barr's Jan 2012 American University TESOL workshop "designed to train your ears and hone transcription skills to improve pronunciation teaching. "

Each vowel has a color key to cue you, eg "Blue Spoon" for [u] "oo."
 

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