For speech recognition systems a method for modeling context-dependent phonetic categories using artificial neural nets has been described. First, linguistically motivated context-clustering is employed to reduce the number of context-dependent categories. Second, phone-specific MLP structures...http://www.google.de/patents/US5745649?utm_source=gb-gplus-sharePatent US5745649 - Automated speech recognition using a plurality of different multilayer perception structures to model a plurality of distinct phoneme categories 
