  Recent advances in neural network based acoustic modelling have shown
significant improvements in automatic speech recognition (ASR) performance. In
order for acoustic models to be able to handle large acoustic variability,
large amounts of labeled data is necessary, which are often expensive to
obtain. This paper explores the application of adversarial training to learn
features from raw speech that are invariant to acoustic variability. This
acoustic variability is referred to as a domain shift in this paper. The
experimental study presented in this paper leverages the architecture of Domain
Adversarial Neural Networks (DANNs) [1] which uses data from two different
domains. The DANN is a Y-shaped network that consists of a multi-layer CNN
feature extractor module that is common to a label (senone) classifier and a
so-called domain classifier. The utility of DANNs is evaluated on multiple
datasets with domain shifts caused due to differences in gender and speaker
accents. Promising empirical results indicate the strength of adversarial
training for unsupervised domain adaptation in ASR, thereby emphasizing the
ability of DANNs to learn domain invariant features from raw speech.
