What Frozen Speech Embeddings Reveal About Audio Deepfake Detection Difficulty

Yashas Harshad Patil, Krish Rawat, Anup Shanbhag


Abstract
Audio deepfake detectors perform unevenly across synthesis systems. Can frozen speech representations expose structure behind this variation? We construct a simple direction between genuine and synthetic WavLM embeddings and characterize each system’s position and spread along it. Across 61 MLAAD text-to-speech system–language groups, projected spread is strongly associated with mean detector difficulty across three runs (𝜌=0.60). It is the only feature surviving correction over 83 recorded tests, and leave-one-system-out ridge prediction gives R2=0.277. The genuine–synthetic directions also differ markedly across corpora, revealing domain-dependent representation geometry. As an auxiliary utterance score, the centroid projection reduces MLAAD detector equal error rate from 27.2% to 16.3%, improving on both component scores. Supervised probe comparisons further identify where adaptation gains originate. Together, these results establish a compact representation-space diagnostic of attack-specific detector behavior; the informative statistic and benefits of score adaptation depend on the corpus and detector.
Anthology ID:
2026.trustaudio-1.1
Volume:
Proceedings of the Workshop on Secure, Safe, and Privacy-Preserving Speech and Audio AI (TrustAudio 2026)
Month:
November
Year:
2026
Address:
Hengqin, Zhuhai, China
Editors:
Nancy F. Chen, Yiming Chen, Xiaoxue Gao, Haizhou Li, Björn Schuller, Berrak Sisman, Xianghu Yue
Venues:
TrustAudio | WS
SIG:
Publisher:
Association for Computational Linguistics
Note:
Pages:
1–10
Language:
URL:
https://aclanthology.org/2026.trustaudio-1.1/
DOI:
Bibkey:
Cite (ACL):
Yashas Harshad Patil, Krish Rawat, and Anup Shanbhag. 2026. What Frozen Speech Embeddings Reveal About Audio Deepfake Detection Difficulty. In Proceedings of the Workshop on Secure, Safe, and Privacy-Preserving Speech and Audio AI (TrustAudio 2026), pages 1–10, Hengqin, Zhuhai, China. Association for Computational Linguistics.
Cite (Informal):
What Frozen Speech Embeddings Reveal About Audio Deepfake Detection Difficulty (Patil et al., TrustAudio 2026)
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PDF:
https://aclanthology.org/2026.trustaudio-1.1.pdf