1. Speech and Hearing Bioscience and Technology Program, Harvard-MIT Division of Health Sciences and Technology, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, Massachusetts 02139
2. Speech Communication Group, Research Laboratory of Electronics, Massachusetts Institute of Technology, 50 Vassar Street, Cambridge, Massachusetts 02139
3. Department of Cognitive and Neural Systems, Boston University, 667 Beacon Street, Boston, Massachusetts 02215