In December 2009 I first read about the Klatt voices in a post on NVDA mailing list. After some initial testing, I filed a Ubuntu bug report(LP: #510182) requesting to include this version into Ubuntu. Eddie Hung build Espeak packages for testing on Ubuntu Lucid development release.
Meanwhile Luke Yelavich mentioned that we can't include unstable software releases and I wrote to espeak developer Jonathan Duddington to make a stable release just in time before the lucid code freeze. Luke and Jonathan managed resolve the technical problems, thanks to them you can now try out the espeak voice variants. Give it a try!
espeak -v 'en-us+klatt2' "This is espeak test"
Storm dargon responded to my email request to provide the steps to enable the klatt2 voice for US english. Here is how you enable them to use with orca screen reader.
cp en-us en-us.bak
sudo gedit en-us
#move to the end of the file press enter and type: klatt 2
#save the file and exit. Espeak will change to klatt 2 automatically.
Someone once commented "espeak voice sounds like a 1960's science fiction robot" and I think its true. Right now we should work to make them better, Interested Anyone?