Cross-domain speech recognition using nonparallel corpora with cycle-consistent adversarial networks

Automatic speech recognition (ASR) systems often does not perform well when it is used in a different acoustic domain from the training time, such as utterances spoken in noisy environments or in different speaking styles. We propose a novel approach to cross-domain speech recognition based on acoustic feature mappings provided by a deep neural network, which is trained using nonparallel speech corpora from two different domains and using no phone labels. For training a target domain acoustic model, we generate “fake” target speech features from the labeleld source domain features using a mapping Gf. We can also generate “fake” source features for testing from the target features using the backward mapping Gb which has been learned simultaneously with G f. The mappings G f and Gb are trained as adversarial networks using a conventional adversarial loss and a cycle-consistency loss criterion that encourages the backward mapping to bring the translated feature back to the original as much as possible such that Gb(Gf (x)) ≈ x. In a highly challenging task of model adaptation only using domain speech features, our method achieved up to 16 % relative improvements in WER in the evaluation using the CHiME3 real test data. The backward mapping was also confirmed to be effective with a speaking style adaptation task.