An Empirical Study of the Effects of Pure Real-World Conditions on the Reliability of Forensic Phonetic Features

Abstract

Forensic phonetic features have been being the most commonly used features in forensic voice comparison technology, and few dispute that they are dramatically affected by real-world conditions, which leads to within-speaker variations and consequently reduces the reliability of forensic voice comparison results as evidence. In this study two experiments are designed and the conversations recorded in pure real-world conditions are adopted as experiment materials to respectively demonstrate the effects of real-world conditions on quantitative phonetic feature of formant trajectory and qualitative phonetic feature of formants pattern that have been tested valid in researches or practice. The results of experiments vividly display that pure real-world conditions do reduce both the amount and quality of available quantitative and qualitative phonetic features, which consequently makes forensic voice comparison impossible or forensic voice comparison results less valid and reliable.