Vowel production significantly contributes to speech intelligibility. Particularly when working with Deaf and Hard-of-hearing students (Hoh), it's important to consider how much of the sound production is not visible. Many vowels appear similar in production if looking at the face alone. To make this information more accessible to Deaf and Hoh students, use multimodal cues to enhance information.

Similarly to teaching consonant production using place, manner, and voice, it is possible to explicitly teach production of vowels. Students may benefit from improving letter-sound correspondence (e.g. "A" can represent many sounds, including /a, æ, əɪ/), reviewing differences between diphthongs and monophthongs, exploring how tongue position changes vowels, and comparing formants of different vowels.

Multimodal feedback and cues may include:

• Spectrograms: Vowel formants are visible and distinct on spectrograms. Students can use this as real-time feedback to adjust vowel production. This can be observed for both vowels in isolation and vowels within words.
• Visual Charts and Graphics: Use of visuals, such as the vowel quadrilateral, can help support Deaf and Hoh students' understanding of the different places in the mouth where vowels occur.
• Handshapes, Gesture, and Cued Speech: Some students may benefit from handshapes (e.g., ASL alphabet letter HS produced while voicing the sound) that provide visual feedback as to which vowel was produced. Cued speech, for example, can be particularly helpful for demonstrating diphthongs, as these cues incorporate moving from one position to a second
• Minimal Pairs (e.g. cup vs. cap, sweet vs. sweat, slip vs. sleep): Particularly when a vowel error changes a word's meaning, minimal pairs can help students recognize this occurrence. This approach is a functional way to reinforce the importance of accurate vowel production to ensure a speaker's intended message is understood.