word boundary- hypothesisation in hindi speech - Speech and ...

increase with increasing mismatch. A plot of the number of alternate word strings
against the mismatch for a sentence is shown in Fig.3.5. It can be seen that the growth
rate in the number of alternate word strings is still exponential.
The performance of the lexical analyser was also measured in terms of the time
spent on the lexical analysis. These results are shown in Table - 3.6. It can be seen that
the time spent on lexical analysis is small when the input sentence contained word
boundaries. A plot of the time against the mismatch is shown in Fig.3.6. It can be seen
that the increase in the time spent is also small.
3.5 Comparison of the lexical analysis results
To estimate the effect of word boundaries on the performance of the lexical
analyser, the results of the above two studies were compared. From the results of the
previous sections, it can be seen that the number of word sequences matching an input
sentence decreased when word boundaries were present in the input. This is illustrated
in Fig.3.7, where the ratio between the number of alternate word strings for the two
cases: (i) when the input sentences had no word boundaries, and (ii) when the input
sentences had all the word boundaries, is plotted against the mismatch cost. It can be
seen that the ratio, which represents the factor of reduction in the number of alternate
word boundary sequences, increases with increasing mismatch. However, it can also be
seen that the reduction is quite small (about 2.3 at a mismatch of 5). Moreover, the
growth in the ratio is also small, indicating that for small errors, one cannot expect
significant reduction in the number of alternate word strings produced by the lexical
analyser due to word boundaries.
On the other hand, a comparison of the times spent on lexical analysis shows a
significant improvement when the word boundaries were present in the input. To
illustrate this, the ratio of the lexical analysis times for a sentence for the cases: (i)
when the input sentences had no word boundaries, and (ii) when the input sentences