flite

https://github.com/kubo/ruby-flite

Ruby-flite is a small speech synthesis library for ruby using CMU flite[http://cmuflite.org]. CMU Flite (festival-lite) is a small, fast run-time synthesis engine developed at CMU and primarily designed for small embedded machines and/or large servers. Flite is designed as an alternative synthesis engine to Festival for voices built using the FestVox suite of voice building tools.