Over the years, sophisticated techniques for utilizing the prior knowledge in the form of text-derived language model and in pronunciation lexicon evolved. However, their use has an undesirable effect: unexpected lexical items (words) in the phrase are replaced by acoustically acceptable in-vocabulary items . This is the major source of error since the replacement often introduces additional errors [2, 3]. Improving the machine ability to handle these unexpected words would considerably increase the utility of speech recognition technology.
Bibliographic reference. Ketabdar, Hamed / Hannemann, Mirko / Hermansky, Hynek (2007): "Detection of out-of-vocabulary words in posterior based ASR", In INTERSPEECH-2007, 1757-1760.