Patent ID: 7584098

Claim:
A method of identifying a location of a query string in an audio signal, the method comprising: receiving a query string; selecting a segment of the audio signal from a plurality of segments of the audio signal; determining a probability of the query string given the segment of the audio signal by determining the product of probabilities of overlapping sequences of tokens, the probabilities of overlapping sequence of tokens formed through steps comprising: applying the audio speech signal to a speech recognizer that identifies a lattice of tokens from the audio speech signal and that assigns a probability to each token in the lattice based on the degree to which the audio speech signal matches an acoustic model for the token; determining expected term frequencies for overlapping sequences of tokens in the lattice through steps comprising: for each path through the lattice: determining a probability of the path by multiplying the probabilities of the tokens along the path together; and at each token along the path updating an expected term frequency for an overlapping sequence of tokens that ends at the token by adding the probability of the path to a current expected term frequency for the overlapping sequence of tokens; and determining the probability of an overlapping sequence of tokens based on the expected term frequency for the overlapping sequence of tokens; using the probability of the query string given the segment of the audio speech signal to identify whether the segment of the audio speech signal is likely to contain the query string.