>Is there a free database of Japanese phonetically balanced isolated words

I have not seen one, but that does not mean that one might not exist.

You might try the Julius Forum.  The Juilus web page states:

More various types of Japanese N-gram LM and acoustic models are available at CSRC. For more detail, please contact [email protected].

YOu might try thr CSRC to see if they have a free corpus.

Another option might be to contact the developers of a opene source text-to-speech engine, and see if they have any free audio ( like the MBROLA Project or the HTS project (more links on this page)

--- (Edited on 11/29/2011 12:14 pm [GMT-0500] by kmaclean) ---