Continual Unsupervised Domain Adaptation for Audio Deepfake Detection

Audio deepfake detection (ADD) aims to verify the authenticity of audio. However, its performance declines sharply when facing significant domain discrepancies caused by unknown datasets. Unsupervised domain adaptation (UDA) has been applied to mitigate domain mismatch. However, as generative models evolve, existing UDA methods struggle with catastrophic forgetting when facing continuously emerging spoofing methods. To address this challenge, we introduce continual UDA for ADD, which involves sequentially training across multiple target domains with continual learning. We propose a causality-distillation-based continual domain adversarial training framework for continual UDA, called CD-DAT. Specifically, we employ the domain adversarial training (DAT) framework to learn both spoofing-discriminative and domain-invariant deep features. In addition, we design a continual learning algorithm utilizing causality distillation to capture the mapping between utterances and classes, effectively mitigating forgetting and maintaining generalization. Experiments demonstrated that CD-DAT improved detection performance across all domains, confirming its memory stability and learning plasticity.