Speech watermarking: an approach for the forensic analysis of digital telephonic recordings

TL;DR

This paper presents a digital speech watermarking method using spread spectrum techniques for forensic authentication of telephonic recordings, enabling reliable verification and embedding relevant metadata without impairing speaker identification.

Contribution

The authors introduce a novel digital signal processing approach for speech watermarking that works across various digital recording devices and preserves forensic analysis capabilities.

Findings

Watermarking does not significantly affect speaker identification.

The method allows embedding of recording metadata like date and time.

Approach is applicable to common digital telephonic recordings.

Abstract

In this article, the authors discuss the problem of forensic authentication of digital audio recordings. Although forensic audio has been addressed in several articles, the existing approaches are focused on analog magnetic recordings, which are less prevalent because of the large amount of digital recorders available on the market (optical, solid state, hard disks, etc.). An approach based on digital signal processing that consists of spread spectrum techniques for speech watermarking is presented. This approach presents the advantage that the authentication is based on the signal itself rather than the recording format. Thus, it is valid for usual recording devices in police-controlled telephone intercepts. In addition, our proposal allows for the introduction of relevant information such as the recording date and time and all the relevant data (this is not always possible with classical systems). Our experimental results reveal that the speech watermarking procedure does not interfere in a significant way with the posterior forensic speaker identification.