Empirical Comparison of Analog and Digital Auditory Preprocessing for Automatic Speech Recognition

Todd M. Massengill, D. M. Wilson, Paul E. Hasler and David W. Graham

Results from digital and analog filter bank preprocessors are compared in order to establish the validity of analog processing for automatic speech recognition (ASR) systems. Three systems are evaluated using speaker and context independent phoneme recognition tasks. The three ASR systems are identical except for the preprocessing techniques used to derive three signal representations: extraction of 1)the digital mel-frequency spectrum, 2)the mel-frequency spectrum from commercial discrete bandpass filters and 3)the exponential spectrum from an analog VLSI bandpass filter bank. The discrete analog system exhibits a 38% increase in recognition accuracy over the digital preprocessing technique. The digital and analog VLSI-based techniques perform comparably (within 3% of each other).