REPORT com-03-08/IDIAP Information Retrieval on Noisy Text Grangier, David Vinciarelli, Alessandro Bourlard, Hervé Information Retrieval Noisy Text Speech Spoken Documents Retrieval EXTERNAL PUBLIC Idiap-Com-08-2003 2003 IDIAP Spoken Document Retrieval (SDR) consists in retrieving segments of a speech database that are relevant to a query. The state-of-the-art approach to the SDR problem consists in transcribing the speech data into digital text before applying common Information Retrieval (IR) techniques. The transcription, produced by an Automatic Speech Recognition system, contains recognition errors. These errors can be referred to as noise. This thesis investigates the effect of this noise on the retrieval process. We compare the results obtained with clean and noisy data at different steps of the retrieval process. To perform such a task, standard IR measures (precision, recall, break-even point, etc.) are used. It is shown that even with very different error rates (10\% vs 30\%,',','), the performances obtained over noisy text are only slightly lower than those over clean text (9\% degradation of average precision for our complete IR system, 45.2\% vs 41.2\%).