Design issues in developing speech corpus for Indian languages — A survey

Any spoken language system, it may either be a speech synthesis or a speech recognition system, starts with building a speech corpora. We give a detailed survey of issues in building a speech corpus for Indian languages. To begin with, an appropriate text file should be selected for building the speech corpus. Then a corresponding speech file is generated and stored. This speech file is the phonetic representation of the selected text file. The speech file is processed in different levels viz., paragraphs, sentences, phrases, words, syllables and phones. These are called the speech units of the file. Researches have been done taking these units as the basic unit for processing. This paper analyses the researches done using phones, diphones, triphones, syllables and polysyllables as their basic unit for speech synthesis. Concatenative speech synthesis involves the concatenation of these basic units to synthesize a natural sounding speech. The speech units are added with some more relevnt information about each unit, manually or automatically, based on an algorithm. The database consisting of the units along with their associated information is called as the speech corpus. Techniques that are used in the database to improve the intelligibility of the synthesized speech in Speech synthesis system are also surveyed.