  In this paper, we have analyzed the impact of confusions on the robustness of
phoneme recognitions system. The confusions are detected at the pronunciation
and the confusions matrices of the phoneme recognizer. The confusions show that
some similarities between phonemes at the pronunciation affect significantly
the recognition rates. This paper proposes to understand those confusions in
order to improve the performance of the phoneme recognition system by isolating
the problematic phonemes. Confusion analysis leads to build a new hierarchical
recognizer using new phoneme distribution and the information from the
confusion matrices. This new hierarchical phoneme recognition system shows
significant improvements of the recognition rates on TIMIT database.
