Order-Free Spoken Term Detection

In this paper, we propose Time-Marked Word (TMW) lists as a replacement for the lattices and Confusion Networks (CNs) widely used as indexing vehicles for Spoken Term Detection (STD). In a TMW list, candidates are simply tagged with posterior probabilities and time information and stored as a large list of words: the additional ordering present in a lattice or CN is discarded. TMW lists compactly summarize a large ASR search space. Representing a large search space is critical for STD metrics such as ATWV that heavily penalize misses of rare keywords. Comparisons on the OpenKWS 2014 Tamil limited language pack task [1] show that the new TMW-based indexing results in better performance while being faster and having a smaller footprint.