A fast vocabulary independent algorithm for spotting words in speech

In applications such as audio-indexing, spoken message retrieval and video-browsing, it is necessary to have the ability to detect spoken words that are outside the vocabulary of the speech recognizer used in these systems, in large amounts of speech at speeds many times faster than real-time. In this paper we present a fast, vocabulary independent, algorithm for spotting words in speech. The algorithm consists of a preprocessing stage and a coarse-to-detailed search strategy for spotting a word/phone sequence in speech. The preprocessing method provides a phone-level representation of the speech that can be searched efficiently. The coarse search, consisting of phone-ngram matching, identifies regions of speech as putative word hits. The detailed acoustic match is then conducted only at the putative hits identified in the coarse match. This gives us the desired accuracy and speed in wordspotting. Overall, the algorithm has a speed of execution that is 2400 times faster than real-time.