Warped Minimum Variance Distortionless Response based bottle neck features for LVCSR

This paper presents the results of our experiments on bottleneck feature applied to a wMVDR (Warped Minimum Variance Distortionless Response) frontend. We examine how to best optimize wMVDR-BNF features and wMVDR combined with MFCC bottleneck features (wMVDR+MFCC-BNF). Our wMVDR+MFCC-BNF frontend improves a single pass system from 18.7% (20.7%) to 18.1% compared to a MFCC-BNF (MFCC) system tested on the Quaero 2010 German evaluation set. When used in a system combination our wMVDR-BNF and wMVDR+MFCC-BNF systems reduced the overall WER from 14.3% to 13.3% on the IWSLT 2010 test set while at the same time reducing the number of systems needed from 9 to 5. Our result of 11.9% on the 2012 IWSLT testset is better than the best result submitted during the evaluation campaign.