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Phonetics Laboratory
Faculty of Linguistics, Philology, and Phonetics

IPOX Speech Synthesizer


IPOX is an experimental, all-prosodic speech synthesizer, developed many years ago by Arthur Dirksen and John Coleman. It is still available for downloading, and was designed to run on a 486 PC running Windows 3.1 or higher, with a 16-bit Windows-compatible sound card, such as the Soundblaster 16. It still seems to run on e.g. XP, but I haven't tried it on Vista.

Please note that IPOX is a rule compiler, not a text-to-speech system. With the codes bundled in the package, it can be used to generate short words in English, using a phonemic input (not normal spelling). It is also possible to adjust the relative durations of syllables (e.g. to alter the rhythm), and using a parameter editor, to tinker with the Klatt parameter files produced by IPOX in order to improve the quality of the sound files that it generates. It has been successfully used by researchers at many institutions to generate synthetic speech files for use in speech perception experiments.

Please take note that the documentation (in the form of Windows Help files) is  incomplete. Because neither of us has any continuing motivation to develop IPOX further, we have no plans for upgrades etc. It is what it is, an experimental/prototype. Note that if you are looking for a text-to-speech system, this is not one!

Arthur Dirksen's 1995 lecture notes about IPOX are a useful source of additional, unpublished information about the system.



Send any comments, questions or bug reports to john.coleman@phon.ox.ac.uk.

Although we are grateful for feedback, we do not offer any kind of support, and we do not undertake to reply. Please accept our apologies for that now.


On-line reference material

On-line information about IPOX and related systems is available from the following sources:

  • Demos

  • Audio demonstrations complementing our 1997 paper `All-Prosodic Speech Synthesis' (In J. P. H. van Santen, R. W. Sproat, J. P. Olive and J. Hirschberg, eds.) Progress in Speech Synthesis. New York: Springer-Verlag. 91-108.
    A few examples of Hindi-Urdu synthesis can be heard here.
  • YorkTalk Home Page

  • This page describes YorkTalk, the system which inspired the development of IPOX.
Arthur Dirksen / Fluency Speech Technology

John Coleman / Oxford University Phonetics Laboratory

IPOX Availability and Registration

IPOX is freely available for evaluation and non-profit research purposes. However, you are required to register your copy by filling in the form below.

To obtain a copy of IPOX, download the following files:

To install IPOX, follow the instructions in the file readme.txt


Registration form

Please fill in the form and click the Submit button.