The sound track is then broken down into 'Phonemes' or 'Phonetic syllables'.

Phoneme is the sound produced while uttering the word. Combination of phonemes forms a word. It is a basic unit of any language.
(Reference: https://en.wikipedia.org/wiki/Phoneme)

The Images of sound track are divided into phonemes.

Number of frames required for each syllable is counted and written down in the exposure sheet.