An Automatic, Simple Ultrasound Biofeedback Parameter for Distinguishing Accurate and Misarticulated Rhotic Syllables. - Sarah R. Li; Colin T. Annand; Sarah Dugan; Sarah M. Schwab; Kathryn J. Eary; Michael Swearengen; Sarah Stack; Suzanne Boyce; Michael A. Riley; T. Douglas Mast (Interspeech, 2021)