Speech encryption in the transform domain
Sridha Sridharan, Ed Dawson, B. Goldburg · Electronics Letters · 1990
A comparison has been made of the use of five discrete orthogonal transforms in speech encryption systems. Four objective measures were used to grade the encryption systems with respect to residual intelligibility and recovered voice quality. A figure of merit based on all the objective measures was formed which gave good correlation to the subjective results of residual intelligibility and recovered speech quality.