This paper examines some versions of Lithuanian and Russian synthetic speech intelligibility and Lithuanian, Russian, Hungarian and Italian synthetic speech acceptability. The speech of both Russian and Lithuanian speaker is more intelligible than Russian or Lithuanian synthesis. Previous version of Russian synthesis is worse than Lithuanian and improved Russian synthesis (IRS). Study of characteristics of IRS sounds shows two opposite tendencies - according to the general quantity of mistake reduction this version is tending towards the natural speech, but according to the homogeneity of mistakes, it moves away. As the first tendency is clearly dominant, the general resultant in the new version shows a tend to improve.
Correlation between intelligibility and acceptability of IRS deals possibility of small progress towards the natural speech. The IRS is more acceptable to subjects than previous version. The old synthesis is viewed as a rather decent instance of a robot's speech, while the IRS - as a poor variant of human speech.
Acceptability studies showed natural speech more enjoyed by Hungarian listeners and more critical by Italian. All versions of synthetic speech were judged as less acceptable than natural but after improvement most of listeners changed their mind.