Dynamic knowledge condensation with audio-selective transformer for audio deepfake detection

The rapid evolution of audio deepfakes has raised significant challenges for the security and reliability of voice-driven systems. While recent detection frameworks achieve high accuracy in controlled environments, their performance often degrades under real-world conditions involving codec compression, signal preprocessing, or domain shifts. To address these challenges, we propose dynamic knowledge condensation with audio-selective transformer (DK-CAST), a novel tri-stream knowledge distillation framework designed for robust audio deepfake detection. DK-CAST employs a high-capacity XLS-R teacher trained on clean speech to supervise a compact student model operating on degraded and preprocessed audio. The student employs a custom audio-selective transformer with dual-stream encoding, dynamic fusion, and phoneme-gated attention to emphasize linguistically relevant cues. Knowledge is transferred via multi-level supervision, including logits, embeddings, and phoneme posteriors, and modulated through a codec-aware loss weighting scheme. To enhance generalization, DK-CAST also includes a compression-agnostic embedding alignment module based on MMD and Center Loss. Evaluations on ASVspoof 2019-LA and ASVspoof 2021-DF demonstrate state-of-the-art performance, achieving EERs of 0.38 and 2.18%, respectively. Furthermore, DK-CAST maintains strong performance under codec degradation, achieving an EER of 3.01% on ASVspoof 2021-DF when tested under MP3 compression.