Syllable Circles are interactive visualizations representing prominence as a feature in short phrases or multi-syllable words. They were designed for computer-aided pronunciation teaching. This study explores whether and how interactive visualizations can affect language learners' awareness of prominence, or stress, in English pronunciation. The study followed seven learners and three teachers. Think-aloud protocols, notes from direct observation, and interviews allowed for six streams of data. It was found that interactive visualizations of Syllable Circles facilitate learners' noticing of prominence. Learners and teachers believed interactive visualizations were a useful means for presenting prominence and other suprasegmental features, and would be valuable learning and teaching resources.