Automatic speech recognition (ASR) involves the transformation of acoustic speech signal captured by a microphone, a telephone, or other transducers, into a text sequence. It is also known as the recognition of speech by a machine or, by some artificial intelligence. However, in spite of focused research in this field for the past several decades, robust speech recognition with high reliability has not been achieved as it degrades in the presence of speaker variabilities, channel mismatch conditions, and in noisy environments. The superb ability of the human auditory system has...