Abstract: An improved topic discriminator includes an integrated speech recognizer or word and phrase spotter as part of a speech event detector, and a topic classifier trained on topic-dependent event frequencies. The event frequencies are determined from either or both transcribed data with a text event detector and untranscribed speech data with a speech event detector. In accordance with another aspect of the present invention, the phrase spotter is used to detect the presence of phrases without the need of parsing the output of a speech recognizer's hypothesized transcription. In accordance with another aspect of the invention, an improved technique is used to select a subset of the potential speech events on whose event frequencies the topic discrimination decision is made. Finally, in accordance with another aspect of the invention, an improved method of topic modeling is used to improve the performance of the topic discriminator.