The present paper deals with building the text corpus for unit selection text-to-speech synthesis. During synthesis the target and concatenation costs are calculated and these costs are usually based on the prosodic and acoustic features of sounds. If the cost calculation is moved to the phonological level, it is possible to simulate unit selection synthesis without any real recordings; in this case text transcriptions are sufficient. We propose to use the cost calculated during the test data synthesis simulation to evaluate the text corpus quality. The greedy algorithm that maximizes coverage of certain phonetic units will be used to build the corpus. In this work the corpora optimized to cover phonetic units of different size and weight are evaluated.

One of the components of the text-to-speech synthesis system is the database of sounds. Two Lithuanian diphone databases in the MBROLA format are presented in this paper. The list of phonemes and the list of diphones necessary for Lithuanian text-to-speech synthesis are described. The problem of phoneme combinations that are not used in the Lithuanian language is dealt with in the work. Also, the article is concerned with transcribing a Lithuanian text.

The problem of speech corpus for design of human-computer interfaces working in voice recognition and synthesis mode is investigated. Specific requirements of speech corpus for speech recognizers and synthesizers were accented. It has been discussed that in order to develop above mentioned speech corpus, it has to consist of two parts. One part of speech corpus should be presented for the needs of Lithuanian text-to-speech synthesizers, another part of speech corpus-for the needs of Lithuanian speech recognition engines. It has been determined that the part of speech corpus designed for speech recognition engines has to ensure the availability to present language specificity by the use of different sets of phonemes. According to the research results, the speech corpus Liepa, which consists of two parts, was developed. This speech corpus opens possibilities for cost-effective and flexible development of human-computer interfaces working in voice recognition and synthesis mode.

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This paper presents activities and challenges when implementing information processing technologies for people with hearing and visual impairments. Other than keyboard based input and monitor based for output modalities should be employed for this category of users. More important is that these modalities are crucial element for successful implementation of complex systems designed for disabled people. Some activities carried on in Lithuania implementing applications oriented for disabled people or using speech technologies and targeted to impaired people are presented too.