Title: The effect of correlation on strength of evidence estimates in Forensic Voice Comparison: uni- and multivariate Likelihood Ratio-based discrimination with Australian English vowel acoustics

Authors: Phil Rose

Addresses: Linguistics Program, School of Language Studies, The Australian National University, Canberra, ACT 0200, Australia

Abstract: The consequences of ignoring correlations between features in traditional forensic speaker recognition are investigated. Two likelihood ratio-based discrimination experiments on the same multivariate formant data are described, one taking correlation into account and the other not doing so. The discrimination is performed using Naive Bayes univariate, and multivariate generative Likelihood Ratios (LRs) as discriminant functions, exemplified with Tippett plots and evaluated with the C_llr cost function. It is shown that ignoring within-segment correlation can result in considerable over- or under-estimation of the strength of evidence when traditional features are used, and there is poorer overall discrimination between same-speaker and different-speaker pairs. The use of logistic-regression fusion to handle between-segment correlation is also demonstrated.

Keywords: FVC; forensic voice comparison; likelihood ratio; vowel formants; correlation; logistic-regression fusion; Australian English; speaker recognition; biometrics.

DOI: 10.1504/IJBM.2010.035447

International Journal of Biometrics, 2010 Vol.2 No.4, pp.316 - 329

Published online: 30 Sep 2010 *

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