J. C. Kelly (Ph.D., Purdue, 1948) is Associate Professor of Speech and Director of the Speech and Hearing Clinic, University of Mississippi.

M. D. Steer (Ph.D., Iowa, 1938) is Professor of Speech and Director of the Speech and Hearing Clinic, Purdue University.

This research was carried out under contract with the Office of Naval Research, Special Devices Center, Human Engineering Branch, as Contract N6ori-104, T. O. II, Project NR-782-003, of which this is Technical Report No. SDC 104-2-17. All members of the Purdue Voice Science Laboratory Staff participate in each research study. The authors and Mr. G. L. Draegert and Mr. George Shaffer were the principal investigators in this study.