In this paper, we present a novel system for detecting known audio. We start with Waveprint, an audio identification system that, given a probe snippet, efficiently provides reliable forced-choice ranking of entries from an audio database. For open-set detection, we can re-examine the best-ranked matches from Waveprint using simple temporal-ordering-based processing. The resulting system has excellent detection capabilities for small snippets of audio that have been degraded in a variety of manners, including competing noise, poor recording quality, and cell-phone playback. The system is more accurate than the previous state-of-the-art system while being more efficient and flexible in memory usage and computation.