I don't know John. Since XP, all the components came with the OS - the voice was crude on XP but came very good on Vista. I think SAPI 5 is required plus a voice but I don't know what the other components might be. Voices are quite bulky items. The ones you buy can be hundreds of Meg.
Charles
PS: A Text-to-Speech facility is excellent for listening to long texts, web pages etc. I installed one for the Mandriva / KDE desktop, I am sure Gnome has the equivalent on Ubuntu.