Thank you very much Chris for your answer.
In the screenshoot I've put two indows: on the left side the OpenOffice Writer Window where I've typed some sentences and on the right side the Tools-->Speech Viewer window.
The words typed in OpenOffice Writer and the words that appears on the Speech Viewer should be monstly the same.
But on the Speech Viewer they are all incorrect. Basically some letters are repeated.
For example "Sto" in the OpenOffice Writer becames "Stto" on the Speech Viewer. "provando" becames "pprrovaando" and so on. This happens for all the words, not for a word specifically.
And it happens only when I use OpenOffice Writer and Microsoft Word.
For this reason I think that Dicionary Pronounciation is not the solution.
Anyway I thank you very much for your help.