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

speech signal-to-symbol conversion in the VOIS speech-to-text conversion system
[Eswar 19901.
From the cost matrix the cost nf substitlition for phonemes was estimated in the
following fzshioc: Let p be the observed phcriemc and q be the lnatching i;honeme.
Then the cost of substituting p by q during the lexical analysis was given by
C(p,q) = 0, if P =q;
C(p,q) = 1, if the row for p in the cost matrix contains q with a 'low' cost;
C(p,q) = 2, if the cost matrix contains 'mid';
C(p,q) = 4, if the cost matrix contains 'high';
C(p,q) is infinite; if there is no entry for q in the row for p.
In Fig.3.2, a small sentence segment, 'mcm na-m m-m was matched against the
lexicon and the various stages in matching are shown. As seen from the figure, initially
two words me: and me:rc were hypothesised as matching the initial portior? of the
input with zero cost and m l, me-la. and mai with a cost of one. From these, the lowest
cost alternative me:ra- was selected for further matching, producing the word strings
mra- M=, me.-ra- mzm with zero cost and me:ra.- na, rne:ru- nam, me:ra-.narnr and
me.m mu- with a cost of one. These word strings were then stored back in the memory
and match process was repeated. The figure shows all partial word sequences produced
by the match whose costs were less than or equal to 1. It can be seen that many of the
partial word sequences (for example, the word string me= nu-) were eliminated due
to the threshold on the maximum cost (one substitution). Complete word strings
I
matching with cost less than or equal to the maximum cost are shown highlighted in the
figure along with their cost.
33 Lexical analysis without word boundaries
The first study on the lexical analyser is to estimate its performance when the
input phoneme string contained no word boundaries. Two parameters were used to