- Iowa Children's Vowel Test requires the identification of a monosyllabic word from a closed set of four words (e.g., toe, toy, tie, two) varying only in vowel content (place and height). Ifthe child performs at 80% or higher, multi-talker babble at a +7 dB-C SIN will be added. It will be administered in both the unilateral and bilateral listening conditions at 70 dB C.