A comparison of procedures for the calculation of forensic likelihood ratios from acoustic-phonetic data: Multivariate kernel density (MVKD) versus Gaussian mixture model-universal background model (GMM-UBM)

  • Authors:
  • Geoffrey Stewart Morrison

  • Affiliations:
  • School of Language Studies, Australian National University, Canberra, ACT 0200, Australia and Forensic Voice Comparison Laboratory, School of Electrical Engineering & Telecommunications, Universit ...

  • Venue:
  • Speech Communication
  • Year:
  • 2011

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Abstract

Two procedures for the calculation of forensic likelihood ratios were tested on the same set of acoustic-phonetic data. One procedure was a multivariate kernel density procedure (MVKD) which is common in acoustic-phonetic forensic voice comparison, and the other was a Gaussian mixture model-universal background model (GMM-UBM) which is common in automatic forensic voice comparison. The data were coefficient values from discrete cosine transforms fitted to second-formant trajectories of /a@?/, /e@?/, /o@?/, /a@?/, and /@?@?/ tokens produced by 27 male speakers of Australian English. Scores were calculated separately for each phoneme and then fused using logistic regression. The performance of the fused GMM-UBM system was much better than that of the fused MVKD system, both in terms of accuracy (as measured using the log-likelihood-ratio cost, C"l"l"r) and precision (as measured using an empirical estimate of the 95% credible interval for the likelihood ratios from the different-speaker comparisons).