For the most popular x-vector-based approaches to speaker anonymisation, the bulk of the anonymisation can stem from vocoding rather than from the core anonymisation function which is used to substitute an original speaker x-vector with that of a fictitious pseudo-speaker. This phenomenon can impede the design of better anonymisation systems since there is a lack of fine-grained control over the x-vector space. The work reported in this paper explores the origin of so-called vocoder drift and shows that it is due to the mismatch between the substituted x-vector and the original representations of the linguistic content, intonation and prosody. Also reported is an original approach to vocoder drift compensation. While anonymisation performance degrades as expected, compensation reduces vocoder drift substantially, offers improved control over the x-vector space and lays a foundation for the design of better anonymisation functions in the future.

翻译：在基于x-vector的说话人匿名化主流方法中，匿名化的主要效果往往源于声码处理，而非用于将原始说话人x-vector替换为虚构伪说话人x-vector的核心匿名化函数。这一现象阻碍了更优匿名化系统的设计，因为当前缺乏对x-vector空间的精细控制能力。本文研究探讨了声码器偏移的起源，揭示其根源在于替换后的x-vector与语言内容、语调及韵律的原始表征之间存在失配。此外，本文提出了一种创新的声码器偏移补偿方法。尽管匿名化性能会如预期般有所下降，但补偿机制能显著降低声码器偏移，增强对x-vector空间的控制能力，为未来设计更优的匿名化函数奠定基础。