Secure-Access System via Fixed and Mobile Telephone Networks

This paper presents a double-digit system for textdependent speaker verification and text validation that can be accessed with security via a telephone network. A speech recognition and a user authentication scheme are proposed that utilize concatenated phoneme HMMs and operate in a sound-prompted mode. The recognition performance of the system is evaluated through extended simulations on Hidden Markov Models (HMMs) using Perceptual Linear Prediction (PLP), Mel Frequency Cepstral Coefficients (MFCC), as well as Cepstral Mean Subtraction (CMS). The effect of various factors such as the length of the training data, the number of embedded re-estimations, and Gaussian mixtures in training of the HMMs, the use of world models, bootstrapping, and user-dependent thresholds on the performance of speech recognition and speaker verification is also examined.