It has been found that vowel production significantly contributes to speech intelligibility. Real-time spectrograms provide valuable information regarding steady-state characteristics and formant transitions. Students can use this visual feedback in conjunction with auditory feedback to modify vowel production in words and short phrases.
Each vowel has a different "picture" on the spectrogram; these are the formants. Vowels are distinguished by their formant patterns. F1 and F2 are close for /ah/ but far apart for /ee/. This information can be used by students to compare different vowels.
Students get immediate feedback by looking at the spectrogram and often self-correct when they see that they have not produced a target correctly. Here the student practices words with /ee/ and corrects the /ee/ in "seen."
The differences in formant structures of vowels are relatively easy for the student to see on a spectrogram. Even when a student is practicing words for consonant production, there is feedback regarding vowel production, especially /ee/.