Investigation of DNN-HMM and Lattice Free Maximum Mutual Information Approaches for Impaired Speech Recognition

Assistive tools that recognize impaired speech due to neurological disorders are emerging and its a fairly complex task. An Intelligent Impaired Speech Recognition system helps persons with speech impairment to improve their interactions with outside world. Impaired speakers have difficulty in pronouncing words which results in partial or incomplete speech contents. Existing Automatic Speech Recognition systems are not effective for Impaired Speech Recognition due to the speaker specific variations which depend on the severity of the neurological disorders. In this work, we have investigated two important approaches namely, Deep Neural Network-Hidden Markov Model and Lattice Free Maximum Mutual Information approach for effective recognition of impaired speech in Tamil language. The training and testing samples are collected from persons with different neurological disorders at varied intelligibility levels such as high, medium, low and very low. The recognition accuracy is evaluated and compared using two datasets namely 20 acoustically similar words and 50 words Impaired Speech Corpus in Tamil.