Praat uses a file format called textgrids, which are time aligned speech transcripts. This library isn't just a data struct for reading and writing textgrids--many utilities are provided to make it easy to work with with transcripts and associated audio files. This library also provides some other tools for use with praat.

Praat is an open source software program for doing phonetic analysis and annotation of speech. Praat can be downloaded here http://www.fon.hum.uva.nl/praat/