Factored adaptation for separable compensation of speaker and environmental variability

While many algorithms for speaker or environment adaptation have been proposed, far less attention has been paid to approaches which address both factors. We recently proposed a method called factored adaptation that can jointly compensate for speaker and environmental mismatch using a cascade of CMLLR transforms that separately compensate for the environment and speaker variability. Performing adaptation in this manner enables a speaker transform estimated in one environment to be be applied when the same user is in different environments. While this algorithm performed well, it relied on knowledge of the operating environment in both training and test. In this paper, we show how unsupervised environment clustering can be used to eliminate this requirement. The improved factored adaptation algorithm achieves relative improvements of 10–18% over conventional CMLLR when applying speaker transforms across environments without needing any additional a priori knowledge.