Before I present you the list I would like to answer two important questions:

1) Why not use Human voice over?
As a eLearning consultant I would prefer to use a human narration professional. However, you should consider the following factors:

• It is more expensive
• It needs more time
• It is difficult to maintain the training
• Few professional have the necessary skills
• It is difficult to update the eLearning course
• The pace is not steady
• It is difficult to maintain your organizations’ identity

2) If I use text why I need to use voice?
For me it is unacceptable that eLearning organization create courses that they do not have voice. Come on guys are you serious! Are you familiar with the learning styles? How an auditory learner will succeed in your eLearning course? Some people will say that not all computers have speakers or that the voice is annoying. You are going to invest in your employees but you do not have money for headphones! Is it difficult to lower the volume or turn it off? Text and voice are extremely important factors to an eLearning course.

So, let see the list of the free and open source text-to-speech tools for e-Learning.

=> If you know a free or open source text-to-speech tool that is not included in the list I will highly appreciate if you write a comment with a link!

The MBROLA Project
The aim of the MBROLA project, initiated by the TCTS Lab of the Faculté Polytechnique de Mons (Belgium), is to obtain a set of speech synthesizers for as many languages as possible, and provide them free for non-commercial applications.

The Festival Speech Synthesis System
Festival offers a general framework for building speech synthesis systems as well as including examples of various modules. As a whole it offers full text to speech through a number APIs: from shell level, though a Scheme command interpreter, as a C++ library, from Java, and an Emacs interface. Festival is multi-lingual (currently English (British and American), and Spanish) though English is the most advanced.

The MARY 
MARY is an open-source, multilingual Text-to-Speech Synthesis platform written in Java. It was originally developed as a collaborative project of DFKI’s Language Technology lab and the Institute of Phonetics at Saarland University and is now being maintained by DFKI. As of version 4.3, MARY TTS supports German, British and American English, Telugu, Turkish, and Russian; more languages are in preparation. MARY TTS comes with toolkits for quickly adding support for new languages and for building unit selection and HMM-based synthesis voices.

YAKiToMe!
Free text to speech. Uses the world’s best text to speech (TTS) software. Upload documents, cut and paste text or link to feeds. Text reader converts text to speech automatically. Download audio and podcasts. It’s fast and easy to use. Get started right away! No software to download or install.

SpokenText
SpokenText lets you easily convert text in to speech. Record (English, French, Spanish or German) PDF, Word, plain text, PowerPoint files, and web pages, and convert them to speech automatically. Create .mp3 or .m4b (Audio Book) recordings (in English, French, Spanish and German) of any text content on your computer or mobile phone.

eSpeak
eSpeak uses a “formant synthesis” method. This allows many languages to be provided in a small size. The speech is clear, and can be used at high speeds, but is not as natural or smooth as larger synthesizers which are based on human speech recordings. Google has integrated eSpeak, an open source software speech synthesizer for English and other languages, in its online translation service Google Translate. The move allow users of Google Translate to hear translations spoken out loud (text-to-speech) by clicking the speaker icon beside some translations.

Praat
Praat is a free scientific software program for the analysis of speech in phonetics. It has been designed and continuously developed by Paul Boersma and David Weenink of the University of Amsterdam. It can run on a wide range of operating systems, including various Unix versions, Mac and Microsoft Windows (95, 98, NT4, ME, 2000, XP, Vista). The program also supports speech synthesis, including articulatory synthesis.

FreeTTS
FreeTTS is a speech synthesis system written entirely in the JavaTM programming language. It is based upon Flite: a small run-time speech synthesis engine developed at Carnegie Mellon University. Flite is derived from the Festival Speech Synthesis System from the University of Edinburgh and the FestVox project from Carnegie Mellon University.

Festvox
The Festvox project aims to make the building of new synthetic voices more systemic and better documented, making it possible for anyone to build a new voice.

Flite: a small, fast run time synthesis engine
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.

The Epos Speech Synthesis System
Epos is a language independent rule-driven Text-to-Speech (TTS) system primarily designed to serve as a research tool. Epos is (or tries to be) independent of the language processed, linguistic description method, and computing environment.

by Christopher Pappas M.B.A., M.Ed.