Digits to Words Converter for Slavic Languages in Systems of Automatic Speech Recognition

In this paper, a system for digits to words conversion for almost all Slavic languages is proposed. This system was developed for improvement of text corpora which we are using for building of a lexicon or for training of language models and acoustic models in the task of Large Vocabulary Continuous Speech Recognition (LVCSR). Strings of digits, some other special characters (%, €, $, ...) or abbreviations of physical units (km, m, cm, kg, l, \({}^\circ \)C, etc.) occur very often in our text corpora. It is in about 5% cases. The strings of digits or special characters are usually omitted if a lexicon is being built or if the language model is being trained. The task of digits to words conversion in non-inflected languages (e.g. English) is solved by relatively simple conversion or lookup table. The problem is more complex in inflected Slavic languages. The string of digits can be converted into several different word combinations. It depends on the context and resulting words are inflected by gender or cases. The main goal of this research was to find the rules (patterns) for conversion of string of digits into words for Slavic languages. The second goal was to unify this patterns over Slavic languages and to integrate them to the universal system for digits to words conversion.