DIGITAL AUDIO RECORDING



Digital Audio Recording

Digital Audio Recording

Background of the Study

Over the last two decades, federal collaboration with local law enforcement and prosecutors to share intelligence, investigative efforts, and analytical processes through teamwork has demonstrated effectiveness in addressing traditional crimes involving drugs, weapons, gangs, and violence (www.controlrisks.com). By extension, many scholars and practitioners have asserted the importance of forming comparable teams to combat computer crime with the hope of similar positive outcomes (www.interpol.int). Only in recent years have state and local police departments pioneered cybercrime-related task forces consisting of law enforcement personnel, prosecutors, and computer technicians (www.controlrisks.com).

These entities are often created to follow up on tips and complaints received from the public, while also seeking to proactively address forms of interpersonal computer wrongdoing (such as the sexual exploitation of minors online) through investigations and digital forensics (www.interpol.int). Thus, these task forces often pursue traditional crime control objectives of identifying law violators and then locating, apprehending, and contributing to their prosecution and adjudication (www.controlrisks.com), while also attempting to prevent crime through education and public awareness.

Problem Statement

Although the development of state-of-the-art speaker recognition systems has shown considerable progress in the last decade, performance levels of these systems do not as yet seem to warrant large-scale introduction in anything other than relatively low-risk applications. Conditions typical of the forensic context such as differences in recording equipment and transmission channels, the presence of background noise and of variation due to differences in communicative context continue to pose a major challenge (www.interpol.int).

Consequently, the impact of automatic speaker recognition technology on the forensic scene has been relatively modest and forensic speaker identification practice remains heavily dominated by the use of a wide variety of largely subjective procedures. While recent developments in the interpretation of the evidential value of forensic evidence clearly favor methods that make it possible for results to be expressed in terms of a likelihood ratio, unlike automatic procedures, traditional methods in the field of speaker identification do not generally meet this requirement (www.controlrisks.com).

However, conclusions in the form of a binary yes/no-decision or a qualified statement of the probability of the hypothesis rather than the evidence are increasingly criticised for being logically flawed. Against this background, the need to put alternative validation procedures in place is becoming more widely accepted.

Theoretical Framework

Although speaker identification by earwitnesses differs in some important respects from the much more widely studied field of eyewitness identification, there are sufficient parallels between the two for speaker identification by earwitnesses to benefit greatly from a close study of the guidelines that have been proposed for the administration of line-ups in the visual domain. Rapid technical developments in the world of audio technology in which speech and data are increasingly transmitted through the same communication channels may soon blunt the efficacy of traditional telephone interception as an investigative and evidential tool (www.interpol.int).

The gradual shift from analogue to digital recording media and the increasingly widespread availability of digital sound processing equipment as well as its ease of operation make certain ...