15. A computer-readable storage device having instructions stored which, when executed by a processor, cause the processor to perform operations comprising: receiving data corresponding to a text query from a user; retrieving, based on the text query, a spoken document; searching a word index of the spoken document associated with the text query using the text query, to yield first search results; searching a sub-word index of the spoken document associated with the text query using the text query, to yield second search results; and returning, via a computer network and according to the first search results and the second search results, audio segments from the spoken document associated with the text query which correspond to the text query.
18. The computer-readable storage device of claim 15 , wherein searching the word index of the spoken document associated with the text query using the text query further comprises searching the word index for an in-vocabulary portion of the text query.