Laboratory Report: Human-supervised and fully-automatic formant-trajectory measurement for forensic voice comparison – Female voices

Acoustic-phonetic approaches to forensic voice comparison often include analysis of vowel formants. Such methods typically depend on human-supervised formant measurement, which is often assumed to be relatively reliable and relatively robust to telephonetransmission-channel effects, but which requires substantial investment of human labor. Fully-automatic formant trackers require minimal human labor but are usually not considered reliable. This study assesses the effect of variability within three sets of formant-trajectory measurements made by four human supervisors on the validity and reliability of forensic-voice-comparison systems in a high-quality v high-quality recording condition. Measurements were made of the formant trajectories of /iau/ tokens in a database of recordings of 60 female speakers of Chinese. The study also assesses the validity of forensic-voice-comparison systems including a human-supervised and five fully-automatic formant trackers under landline-to-landline, mobile-to-mobile, and mobile-to-landline conditions, each of these matched with the same condition and mismatched with the highFVC, EE&T, UNSW – Laboratory Report 2 quality condition. In each case the formant-trajectory systems were fused with a baseline mel-frequency cepstral-coefficient (MFCC) system, and performance was assessed relative to the baseline system. The human-supervised systems always outperformed the fullyautomatic formant-tracker systems, but in some conditions the improvement was marginal and the cost of human-supervised formant-trajectory measurement probably not warranted.