Vocoder drift compensation by x-vector alignment in speaker anonymisation

TL;DR

This paper investigates vocoder drift in x-vector-based speaker anonymisation, identifies its cause as a mismatch in speech content and prosody, and proposes a compensation method to improve control and anonymisation quality.

Contribution

It introduces a novel approach to compensate for vocoder drift by aligning x-vectors, enhancing control over anonymisation and reducing drift effects.

Findings

Vocoder drift is caused by mismatch between x-vector and speech content.

Compensation significantly reduces vocoder drift.

Improved control over anonymisation process.

Abstract

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.