Learning-based auditory encoding for robust speech recognition

This paper describes ways of speeding up the optimization process for learning physiologically-motivated components of a feature computation module directly from data. During training, word lattices generated by the speech decoder and conjugate gradient descent were included to train the parameters of logistic functions in a fashion that maximizes the a posteriori probability of the correct class in the training data. These functions represent the rate-level nonlinearities found in most mammalian auditory systems. Experiments conducted using the CMU SPHINX-III system on the DARPA Resource Management and Wall Street Journal tasks show that the use of discriminative training to estimate the shape of the rate-level nonlinearity provides better recognition accuracy in the presence of background noise than traditional procedures which do not employ learning. More importantly, the inclusion of conjugate gradient descent optimization and a word lattice to reduce the number of hypotheses considered greatly increases the training speed, which makes training with much more complicated models possible.