Phone duration modeling for LVCSR

Modeling phone durations in a word-specific fashion has previously been shown to lead to improvements in LVCSR recognition performance. We report results on the Switchboard database which confirm that at least small improvements (around 0.2-0.3% absolute) can be obtained. The duration probabilities are applied to time-marked recognition lattices. Features of the system include a novel data-driven method for smoothing discrete distributions, and a form of discrete distribution which allows phone and word lengths to be modeled simultaneously within a consistent probabilistic framework.