Automatic-type calibration of traditionally derived likelihood ratios:Forensic analysis of Australian English /o/ formant trajectories

Abstract

A traditional-style phonetic-acoustic forensic-speaker-recognition analysis was conducted on Australian English /o/ recordings. Different parametric curves were fitted to the formant trajectories of the vowel tokens, and cross-validated likelihood ratios were calculated using a single-stage generative multivariate kernel density formula. The outputs of different systems were compared using C llr, a metric developed for automatic speaker recognition, and the cross-validated likelihood ratios were calibrated using a procedure developed for automatic speaker recognition. Calibration ameliorated some likelihood-ratio results which had offered strong support for a contrary-to-fact hypothesis.