© 2000 Todd Neller.  A.I.M.A. text figures © 1995 Prentice Hall.  Used by permission.
Speech Recognition: language model
•mapping sound waves to a sequence of words
•“It’s hard to wreck a nice beach.”
•Probabilistic Context-Free Grammars (PCFGs)
•P(w1 w2 … wN) = P(w1) * P(w2|w1) * … * P(wN|w1 … w(N-1))
•CPTs too large:
–unigrams: Approximate as P(w1) * P(w2) * … * P(wN)
–bigrams: Approximate as P(w1) * P(w2|w1) * … * P(wN|w(N-1))
–trigrams:Approximate as P(w1) * P(w2|w1) * P(w3|w1,w2)… * P(wN|w(N-1),w(N-2))